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EconoMeter: Sluggish population means slow economy?
Question: Is San Diego County's long-term economic health in danger due to very slow population growth?
Yes, 1; No, 14
Marney Cox, San Diego Association of Governments
Answer: YES
Although population growth does not equal economic growth, at times it can be an indicator of prosperity trends. California and San Diego at one time were strong magnets of economic opportunity and attracted more people into the state and county than moved out, referred to as net domestic migration. Over the past two decades California is 4 million short on this exchange with other states and San Diego has contributed its proportional share to the net exodus. Both are still growing but not because our relative economic opportunities are more appealing - they're not - and some people have voted with their feet.
Is San Diego County's long-term economic health in danger due to very slow population growth?
Yes 41% (16)
No 59% (23)
39 total votes.
Phil Blair, Manpower
Answer: NO
San Diego County's economic growth should not be based merely on population growth. Population growth is a false crutch that does not have a core underpinning. Our economy will thrive on innovative San Diego companies, hiring current talented San Diegans, new startups and outside companies wanting to move into the San Diego region. We need to be educating and training San Diegans, and the natural population growth from their offspring that want to stay in San Diego, for the skills needed for jobs currently open here in San Diego, and for the jobs of the future that this talented workforce will attract. We don't need to depend on outsiders moving into San Diego; we need to depend on ourselves.
Kelly Cunningham, National University System
Answer: NO
It is not so much slow growth, but the type of population growth that is the issue. We are losing a rising generation of workers in their 30s and 40s just entering more productive phases of their careers. Along with losing their skill sets, they take considerable spending power as well as their children to establish families and homes elsewhere. We are left with an aging workforce that will eventually exit the labor market leaving a significant skill gap. We are also increasing the population of un- or less-skilled workers unable to afford living in ever more expensive San Diego.
Gina Champion-Cain, American International Investments
Answer: NO
The county's many positive attributes are far more powerful than the manageable population variances we have seen. San Diego's weather, military complex, biotech, telecom, academic and research hubs all contribute to the base strongly enough to ensure long-term economic stability. The region's challenge is to find an equilibrium between lower wage tourism/service sector jobs, which are here to stay, and more highly compensated sectors, of which many are flight risks. A symbiotic balance between sectors, bolstered by a strong "middle" will ensure long term economic health.
Alan Gin, University of San Diego
Answer: NO
San Diego's economy is heavily impacted by outside forces, e.g., defense spending and tourism. Whether San Diego's population is growing or not, those forces will continue to positively impact the local economy. Potential problems of slow population growth are not enough workers in some industries and reduced consumer spending, which would affect retailers, restaurants, and others. Positives would be a stronger labor market for workers (which could lead to rising wages and incomes), reduced pressure on the housing market, and less demand for government services such as education. Finally, as the local economy recovers, some of the internal migration will reverse, which would help mitigate any problems.
Stephan Goss, Zeeto Media
Goss is not participating this week.
James Hamilton, University of California San Diego
Answer: NO
No. California and San Diego were hit harder than the rest of the country by the recession, and that may be one factor that caused some people to move out. But San Diego house prices are up almost 20 percent over the last year, one of the sharpest increases in the nation. Our unemployment rate fell by 1.5 percentage points over the last year, compared with only a 0.8 percentage point drop for the U.S. as a whole. I expect the San Diego job market to continue to improve over the next year, and that should make a big difference for the local economy.


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Like so many other parents Anne Zehren has plopped her two young sons in front of the TV from time to time to get some work done without worrying too much about it. But what's on the TV and how long it's on — along with computers, videogames and other media — is something all parents should be concerned about, according to Zehren, the president and chief operating officer of Common Sense Media, a nonprofit organization that helps parents make sense of the digital world and offers ways to make informed media decisions for their families. The amount of time kids spend in that digital world is at a crisis level, she believes.
Zehren has been delving into the minds of youths long before she became a first-time mom just days before she turned 42. She was the publisher of Teen People, which let teens dictate the content and issues, and president of sales and marketing for Al Gore's Current TV before joining Common Sense Media in 2003. Earlier this year, Common Sense Media partnered with Disney to get kids and their parents thinking about how to safely navigate the Internet and other digital platforms.
Zehren lives with her husband, Harvey, 9-year-old stepson and 6-year-old son in San Francisco.
In many fields, women who rise to the top are either single or childfree. What has been your experience before you had children and once you became a mom?
I got married when I was 41, and it was very different. I didn't mind staying out late or sleeping in on a Saturday; those days are pretty much have stopped. I try to limit my travel. I race home, take red-eyes, get up at of the middle of dawn to race home to kiss my kids goodnight. I'm constantly shrinking more time into my day at work; before, I might linger around the halls or stay an extra 20 minutes at lunch and now I'm just crunching and crunching and crunching. I make it a rule to be home at 6 at night. That's really important; our kids are so young, they're going to bed at 7:30, 8 o'clock. But, I am going back on the computer at 9, but that's in my time, not theirs.
When I was growing up, we had a few media options — TV, radio, print and my beloved Princess phone. My mother didn't allow comic books, but I still managed to sneak in some Archie and Veronica comics anyway. How has media made parenting easier and how has it made it harder?
Every mom needs that movie they put their child in front of or that TV show or that game to play because it's really hard to find that "me" time, or to blow dry your hair in the morning, and there's nothing wrong with that. If you choose the right stuff, it actually can be good for your kids. What's happened, however, is the media has become "the other parent" in our kids' lives now, and the media might not be imparting values to them that we wanted to impart. The kind of shocking news that brought me to Common Media is that average child in the U.S., when you consider texting, is spending nine hours a day in front of a screen. That's incredibly sad. I think it's a national crisis. As parents, we're competing with this other influential parent and you're asking yourself, "What values are they teaching my child, what kind of role models are they seeing, what are they learning to improve their character and intelligence?"
One of the beliefs of Common Sense Media is that the media industry needs to act responsibly in creating and marketing content. But in a free marketplace, isn't it up to the consumer — in this case, the parents — to ultimately take control of what their kids watch or read?
That used to be the case. In the old days, we had a TV in our living room and parents could talk with their kids or just tell them what they could and couldn't watch. They had control over that TV. Now, it's completely different. The access our kids have to media has changed 100 percent. A television in their bedroom, a laptop on their desk, a gaming console in the basement, and an iTouch in their backpack. They have a cell phone, which is really like having a computer in their pocket, and so the content they're accessing, parents don't have control over. Parents now need to teach their kids to make good decisions on their own.
You used market research and Trendspotters, your own network of ahead-of-the-curve readers, to help marketers and companies shape their decisions. Then you became a mom. Has motherhood changed your perspective, and if so, in what ways?
I've always had a lot of soul and integrity around the marketing process, so I don't know if I would have done anything differently. One of our core beliefs at Teen People was to treat teenagers with respect. I think overall, one of the things I've learned is the responsibility of marketers to think about the impact they're having on kids in terms of their role models they're putting out there, and I think that's especially true for girls. Regrettably, sex and violence sell and often the riskier the content, the higher the audience, I know from experience that having a conscience and doing the right thing can have big audiences and big sales as well.
You've said you joined Common Sense Media because you were "alarmed" by how much time kids spend with media. But our parents probably could have said the same about us once they brought the second TV home. Kids who grow up with the various new media adapt to it and learn how to navigate it quickly. So, what's so alarming especially since parents themselves have started embracing Facebook and online dating and banking?
Parents do need to be role models with technology, and take a break from their Blackberry, iPhone, computer when they're with their kids. … I think the difference with media use is considering the vast differences between adults versus kids. The judgment part of the brain in tweens and teens is not fully developed at all. Combine that with the fact that these are the years where they're pushing boundaries, finding their way, and experimenting, and there's trouble! When our tweens and teens go online to a social network, or text, they're really experimenting in public and potentially leaving a permanent digital footprint at a time when they can't think through things. And they don't quite understand the long-term implications. … Now, if our kids are online and posting and revealing too much information or being unkind, it can be permanent, viral and searchable.
Some women say they could never work full time, others say they could never stay home. Where do you see yourself in that spectrum, and why?
I think my kids would kill me if I stayed at home full time (laughs). That said, I pick up my son Friday at 3 o'clock and he comes to work with me, most days, and hangs out. We have a lot of working mothers at Common Sense Media. I think it's really important for my kids to see me working out of the home. At the same time, I have tremendous respect for women who choose to work in the home. It's probably the hardest job anyone could imagine. The reward for me was, when I asked my son, "What do you want to be when you grow up?" my little 6-year-old, Cole, he paused and said, "You know Mom, I think I want to be the boss." That just kind of thrilled me that he was thinking that way. He was thinking he wanted to be in a leadership role.
You're a mom to one and stepmom to one. What have been some of the challenges of being a blended family?
We're blended in a couple of ways. Yes, I have a stepson and the second is, we're a biracial family; my husband is African-American and I'm Caucasian. So, it's really enriching our family in a number of ways. I think step-parenting is the most unbelievable gift. It's challenging in some of the logistics; my stepson lives in Piedmont and my husband works in Mountain View so logistically it's challenging and takes some time in planning. But both families are incredibly collaborative and cooperative. If I could offer new stepmoms one piece of advice it would be have realistic expectations walking in, to do all you can to honor and reinforce the unique place their birth moms occupy.
What do you think you're sacrificed as a working mom, and what have you gained?
I really don't think I've sacrificed much. There are times when I sigh about not being able to be there in the carpool lane after school and have those little moments with the boys. But in the big picture I feel totally blessed to have such a full life with my kids while working. Luckily, our organization is all about families, so no matter what, families always come first. Whether you have a family or not, I really believe you won't be successful unless you have a full life outside of the office
In what ways has motherhood surprised you?
Oh, it's a crack up. My kids keep me laughing constantly. And you just never realized that your heart could have so much love in it. People talk about it, and there really is that moment when you see that little one staring up at you in your arms at the hospital, and you just cannot really explain the love you feel. And it's amazing how inspiring kids are and how much they teach you about what's important in life. My sons have taught me the importance of imagination, forgiveness, laughter, silliness, play, curiosity and kind hearts.
How do you manage the home-work balance?
It's hard. I find prayer helpful to calm me down. My husband is very helpful despite the fact that he has an hour and a half commute each way. So, we really try to divide and conquer. The mornings are mine and, again, I made a commitment to home at 6 o'clock. We are fortunate to have a great, great nanny. I think it's also very important to pay attention to your spouse, so my husband and I have a date night every Saturday night and sometimes that's just walking around the block but we're doing it together.
When your boys look back on their childhood, what do you hope they'll think of their childhood and you as a mom?
I just hope they feel really cared for. And that my husband and I were an inspiration for them in terms of them reaching their potential, and that we were supportive of them going for their heart's desire.
Common Sense Media President and COO Anne Zehren was interviewed by Vicki Larson, Around the Watercooler [0] contributor. She is a journalist and single mom.

subset: commoncrawl


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PESWiki.com -- Pure Energy Systems Wiki: Finding and Facilitating the Best Exotic Free Energy Technologies
PowerPedia:Quantum mechanics
From PESWiki
Quantum mechanics is a first quantized quantum theory that supersedes classical mechanics at the atomic and subatomic levels. It is a fundamental branch of physics that provides the underlying mathematical framework for many fields of physics and chemistry, including condensed matter physics, atomic physics, molecular physics, computational chemistry, quantum chemistry, particle physics, and nuclear physics. Quantum mechanics is sometimes used in a more general sense, to mean quantum physics.
Terminology and theories
The term quantum (Latin, "how much") refers to discrete units that the theory assigns to certain physical quantities, such as the energy of an atom at rest (see Figure 1, at right). The discovery that waves could be measured in particle-like small packets of energy called quanta led to the branch of physics that deals with atomic and subatomic systems which we today call Quantum Mechanics. The foundations of quantum mechanics were established during the first half of the 20th century by Max Planck, Albert Einstein, Niels Bohr, Louis de Broglie, Werner Heisenberg, Erwin Schrödinger, Max Born, John von Neumann, Paul Dirac, Wolfgang Pauli and others. Some fundamental aspects of the theory are still actively studied.
A quantum theory is a theory of physics that uses Planck's constant. In contrast to classical physics, where variables are often continuous, many of the variables in a quantum theory take on discrete values. The quantum was concept that grew out of the realisation that electromagnetic radiation came in discrete packets, called quanta. The process of converting a classical theory into a quantum theory is called quantisation and is divided into stages: first quantisation, second quantisation, etc depending on the extent to which the theory is quantised. Quantum physics is the set of quantum theories. There are several of them:
- quantum mechanics -- a first quantised or semi-classical theory in which particle properties are quantised, but not particle numbers, fields and fundamental interactions.
- quantum field theory or QFT -- a second or canonically quantized theory in which all aspects of particles, fields and interactions are quantised, with the exception of gravitation. Quantum electrodynamics, quantum chromodynamics and electroweak theory are examples of relativistic fundamental QFTs which taken together form the Standard Model. Solid state physics is a non-fundamental QFT.
- quantum gravity -- a third quantised theory in which general relativity (i.e. gravity) is also quantised. This theory is incomplete, and is hoped to be finalised within the framework of a theory of everything, such as string theory or M-theory.
History of Quantum mechanics
In 1900, the German physicist Max Planck introduced the idea that energy is quantized, in order to derive a formula for the observed frequency dependence of the energy emitted by a black body. In 1905, Einstein explained the photoelectric effect by postulating that light energy comes in quanta called photons. The idea that each photon had to consist of energy in terms of quanta was a remarkable achievement as it effectively removed the possibility of black body radiation attaining infinite energy if it were to be explained in terms of wave forms only. In 1913, Bohr explained the spectral lines of the hydrogen atom, again by using quantization, in his paper of July 1913 On the Constitution of Atoms and Molecules. In 1924, the French physicist Louis de Broglie put forward his theory of matter waves by stating that particles can exhibit wave characteristics and vice versa.
These theories, though successful, were strictly phenomenological: there was no rigorous justification for quantization (aside, perhaps, for Henri Poincaré's discussion of Planck's theory in his 1912 paper Sur la théorie des quanta). They are collectively known as the old quantum theory. The phrase "quantum physics" was first used in Johnston's Planck's Universe in Light of Modern Physics. Modern quantum mechanics was born in 1925, when the German physicist Heisenberg developed matrix mechanics and the Austrian physicist Schrödinger invented wave mechanics and the non-relativistic Schrödinger equation. Schrödinger subsequently showed that the two approaches were equivalent.
Heisenberg formulated his uncertainty principle in 1927, and the Copenhagen interpretation took shape at about the same time. Starting around 1927, Paul Dirac began the process of unifying quantum mechanics with special relativity by discovering the Dirac equation for the electron. He also pioneered the use of operator theory, including the influential bra-ket notation, as described in his famous 1930 textbook. During the same period, Hungarian polymath John von Neumann formulated the rigorous mathematical basis for quantum mechanics as the theory of linear operators on Hilbert spaces, as described in his likewise famous 1932 textbook. These, like many other works from the founding period still stand, and remain widely used. The field of quantum chemistry was pioneered by physicists Walter Heitler and Fritz London, who published a study of the covalent bond of the hydrogen molecule in 1927. Quantum chemistry was subsequently developed by a large number of workers, including the American theoretical chemist Linus Pauling at Cal Tech, and John Slater into various theories such as Molecular Orbital Theory or Valence Theory.
Beginning in 1927, attempts were made to apply quantum mechanics to fields rather than single particles, resulting in what are known as quantum field theories. Early workers in this area included Dirac, Pauli, Weisskopf, and Jordan. This area of research culminated in the formulation of quantum electrodynamics by Feynman, Dyson, Schwinger, and Tomonaga during the 1940s. Quantum electrodynamics is a quantum theory of electrons, positrons, and the electromagnetic field, and served as a role model for subsequent quantum field theories.
The theory of quantum chromodynamics was formulated beginning in the early 1960s. The theory as we know it today was formulated by Politzer, Gross and Wilzcek in 1975. Building on pioneering work by Schwinger, Higgs, Goldstone, Glashow, Weinberg and Salam independently showed how the weak nuclear force and quantum electrodynamics could be merged into a single electroweak force.
Quantum mechanics formalism
Quantum mechanics is a more fundamental theory than Newtonian mechanics and classical electromagnetism, in the sense that it provides accurate and precise descriptions for many phenomena that these "classical" theories simply cannot explain on the atomic and subatomic level. It is necessary to use quantum mechanics to understand the behavior of systems at atomic length scales and smaller. For example, if Newtonian mechanics governed the workings of an atom, electrons would rapidly travel towards and collide with the nucleus. However, in the natural world the electron normally remains in a stable orbit around a nucleus -- seemingly defying classical electromagnetism. Quantum mechanics was initially developed to explain the atom, especially the spectra of light emitted by different atomic species. The quantum theory of the atom developed as an explanation for the electron's staying in its orbital, which could not be explained by Newton's laws of motion and by classical electromagnetism.
In the formalism of quantum mechanics, the state of a system at a given time is described by a complex number wave functions (sometimes referred to as orbitals in the case of atomic electrons), and more generally, elements of a complex vector space. This abstract mathematical object allows for the calculation of probabilities of outcomes of concrete experiments. For example, it allows to compute the probability of finding an electron in a particular region around the nucleus at a particular time. Contrary to classical mechanics, one cannot in general make predictions of arbitrary accuracy. For instance electrons cannot in general be pictured as localized particles in space but rather should be thought of as "clouds" of negative charge spread out over the entire orbit. These clouds represent the regions around the nucleus where the probability of "finding" an electron is the largest. Heisenberg's Uncertainty Principle quantifies the inability to precisely locate the particle. The other exemplar that led to quantum mechanics was the study of electromagnetic waves such as light. When it was found in 1900 by Max Planck that the energy of waves could be described as consisting of small packets or quanta, Albert Einstein exploited this idea to show that an electromagnetic wave such as light could be described by a particle called the photon with a discrete energy dependent on its frequency. This led to a theory of unity between subatomic particles and electromagnetic waves called wave-particle duality in which particles and waves were neither one nor the other, but had certain properties of both. While quantum mechanics describes the world of the very small, it also is needed to explain certain "macroscopic quantum systems" such as superconductors and superfluids.
Broadly speaking, quantum mechanics incorporates four classes of phenomena that classical physics cannot account for: (i) the quantization (discretization) of certain physical quantities, (ii) wave-particle duality, (iii) the uncertainty principle, and (iv) quantum entanglement. Each of these phenomena will be described in greater detail in subsequent sections. Since the early days of quantum theory, physicists have made many attempts to combine it with the other highly successful theory of the twentieth century, Albert Einstein's General Theory of Relativity. While quantum mechanics is entirely consistent with special relativity, serious problems emerge when one tries to join the quantum laws with general relativity, a more elaborate description of spacetime which incorporates gravity. Resolving these inconsistencies has been a major goal of twentieth- and twenty-first-century physics. Despite the proposal of many novel ideas, the unification of quantum mechanics—which reigns in the domain of the very small—and general relativity—a superb description of the very large—remains a tantalizing future possibility. (See quantum gravity, string theory.) Because everything is composed of quantum-mechanical particles, the laws of classical physics must approximate the laws of quantum mechanics in the appropriate limit. This is often expressed by saying that in case of large quantum numbers quantum mechanics "reduces" to classical mechanics and classical electromagnetism. This requirement is called the correspondence, or classical limit.
There are numerous mathematically equivalent formulations of quantum mechanics. One of the oldest and most commonly used formulations is the transformation theory invented by Cambridge theoretical physicist Paul Dirac, which unifies and generalizes the two earliest formulations of quantum mechanics, matrix mechanics (invented by Werner Heisenberg)<ref> Especially since Werner Heisenberg was awarded the Nobel Prize in Physics in 1932 for the creation of quantum mechanics, the role of Max Born has been obfuscated. A 2005 biography of Born details his role as the creator of the matrix formulation of quantum mechanics. This was recognized in a paper by Heisenberg, in 1950, honoring Max Planck. See: Nancy Thorndike Greenspan, "The End of the Certain World: The Life and Science of Max Born (Basic Books, 2005), pp. 124 - 128, and 285 - 286. </ref> and wave mechanics (invented by Erwin Schrödinger). In this formulation, the instantaneous state of a quantum system encodes the probabilities of its measurable properties, or "observables". Examples of observables include energy, position, momentum, and angular momentum. Observables can be either continuous (e.g., the position of a particle) or discrete (e.g., the energy of an electron bound to a hydrogen atom).
Generally, quantum mechanics does not assign definite values to observables. Instead, it makes predictions about probability distributions; that is, the probability of obtaining each of the possible outcomes from measuring an observable. Naturally, these probabilities will depend on the quantum state at the instant of the measurement. There are, however, certain states that are associated with a definite value of a particular observable. These are known as "eigenstates" of the observable ("eigen" meaning "own" in German). In the everyday world, it is natural and intuitive to think of everything being in an eigenstate of every observable. Everything appears to have a definite position, a definite momentum, and a definite time of occurrence. However, Quantum Mechanics does not pinpoint the exact values for the position or momentum of a certain particle in a given space in a finite time, but, rather, it only provides a range of probabilities of where that particle might be. Therefore, it became necessary to use different words for a) the state of something having an uncertainty relation and b) a state that has a definite value. The latter is called the "eigenstate" of the property being measured.
A concrete example will be useful here. Let us consider a free particle. In quantum mechanics, there is wave-particle duality so the properties of the particle can be described as a wave. Therefore, its quantum state can be represented as a wave, of arbitrary shape and extending over all of space, called a wavefunction. The position and momentum of the particle are observables. The Uncertainty Principle of quantum mechanics states that both the position and the momentum cannot simultaneously be known with infinite precision at the same time. However, we can measure just the position alone of a moving free particle creating an eigenstate of position with a wavefunction that is very large at a particular position x, and zero everywhere else. If we perform a position measurement on such a wavefunction, we will obtain the result x with 100% probability. In other words, we will know the position of the free particle. This is called an eigenstate of position. If the particle is in an eigenstate of position then its momentum is completely unknown. An eigenstate of momentum, on the other hand, has the form of a plane wave. It can be shown that the wavelength is equal to h/p, where h is Planck's constant and p is the momentum of the eigenstate. If the particle is in an eigenstate of momentum then its position is completely blurred out.
Usually, a system will not be in an eigenstate of whatever observable we are interested in. However, if we measure the observable, the wavefunction will immediately become an eigenstate of that observable. This process is known as wavefunction collapse. If we know the wavefunction at the instant before the measurement, we will be able to compute the probability of collapsing into each of the possible eigenstates. For example, the free particle in our previous example will usually have a wavefunction that is a wave packet centered around some mean position x0, neither an eigenstate of position nor of momentum. When we measure the position of the particle, it is impossible for us to predict with certainty the result that we will obtain. It is probable, but not certain, that it will be near x0, where the amplitude of the wavefunction is large. After we perform the measurement, obtaining some result x, the wavefunction collapses into a position eigenstate centered at x.
Wave functions can change as time progresses. An equation known as the Schrödinger equation describes how wave functions change in time, a role similar to Newton's second law in classical mechanics. The Schrödinger equation, applied to our free particle, predicts that the center of a wave packet will move through space at a constant velocity, like a classical particle with no forces acting on it. However, the wave packet will also spread out as time progresses, which means that the position becomes more uncertain. This also has the effect of turning position eigenstates (which can be thought of as infinitely sharp wave packets) into broadened wave packets that are no longer position eigenstates. Some wave functions produce probability distributions that are constant in time. Many systems that are treated dynamically in classical mechanics are described by such "static" wave functions. For example, a single electron in an unexcited atom is pictured classically as a particle moving in a circular trajectory around the atomic nucleus, whereas in quantum mechanics it is described by a static, spherically symmetric wavefunction surrounding the nucleus. (Note that only the lowest angular momentum states, labeled s, are spherically symmetric).
The time evolution of wave functions is deterministic in the sense that, given a wavefunction at an initial time, it makes a definite prediction of what the wavefunction will be at any later time. During a measurement, the change of the wavefunction into another one is not deterministic, but rather unpredictable, i.e., random. The probabilistic nature of quantum mechanics thus stems from the act of measurement. This is one of the most difficult aspects of quantum systems to understand. It was the central topic in the famous Bohr-Einstein debates, in which the two scientists attempted to clarify these fundamental principles by way of thought experiments. In the decades after the formulation of quantum mechanics, the question of what constitutes a "measurement" has been extensively studied. Interpretations of quantum mechanics have been formulated to do away with the concept of "wavefunction collapse"; see, for example, the relative state interpretation. The basic idea is that when a quantum system interacts with a measuring apparatus, their respective wavefunctions become entangled, so that the original quantum system ceases to exist as an independent entity. For details, see the article on measurement in quantum mechanics.
As mentioned in the introduction, there are several classes of phenomena that appear under quantum mechanics which have no analogue in classical physics. These are sometimes referred to as "quantum effects". The first type of quantum effect is the quantization of certain physical quantities. Quantization first arose in the mathematical formulae of Max Planck in 1900 as discussed in the introduction. Max Planck was analyzing how the radiation emitted from a body was related to its temperature, in other words, he was analyzing the energy of a wave. The energy of a wave could not be infinite, so Planck used the property of the wave we designate as the frequency to define energy. Max Planck discovered a constant that when multiplied by the frequency of any wave gives the energy of the wave. This constant is referred to by the letter h in mathematical formulae. It is a cornerstone of physics. By measuring the energy in a discrete non-continuous portion of the wave, the wave took on the appearance of chunks or packets of energy. These chunks of energy resembled particles. So energy is said to be quantized because it only comes in discrete chunks instead of a continuous range of energies.
In the example we have given, of a free particle in empty space, both the position and the momentum are continuous observables. However, if we restrict the particle to a region of space (the so-called "particle in a box" problem), the momentum observable will become discrete; it will only take on the values , where L is the length of the box, h is Planck's constant, and n is an arbitrary nonnegative integer number. Such observables are said to be quantized, and they play an important role in many physical systems. Examples of quantized observables include angular momentum, the total energy of a bound system, and the energy contained in an electromagnetic wave of a given frequency. Another quantum effect is the uncertainty principle, which is the phenomenon that consecutive measurements of two or more observables may possess a fundamental limitation on accuracy. In our free particle example, it turns out that it is impossible to find a wavefunction that is an eigenstate of both position and momentum. This implies that position and momentum can never be simultaneously measured with arbitrary precision, even in principle: as the precision of the position measurement improves, the maximum precision of the momentum measurement decreases, and vice versa. Those variables for which it holds (e.g., momentum and position, or energy and time) are canonically conjugate variables in classical physics.
Another quantum effect is the wave-particle duality. It has been shown that, under certain experimental conditions, microscopic objects like atoms or electrons exhibit particle-like behavior, such as scattering. ("Particle-like" in the sense of an object that can be localized to a particular region of space.) Under other conditions, the same type of objects exhibit wave-like behavior, such as interference. We can observe only one type of property at a time, never both at the same time. Another quantum effect is quantum entanglement. In some cases, the wave function of a system composed of many particles cannot be separated into independent wave functions, one for each particle. In that case, the particles are said to be "entangled". If quantum mechanics is correct, entangled particles can display remarkable and counter-intuitive properties. For example, a measurement made on one particle can produce, through the collapse of the total wavefunction, an instantaneous effect on other particles with which it is entangled, even if they are far apart. (This does not conflict with special relativity because information cannot be transmitted in this way.)
Mathematical formulation
In the mathematically rigorous formulation of quantum mechanics, developed by Paul Dirac and John von Neumann, the possible states of a quantum mechanical system are represented by unit vectors (called "state vectors") residing in a complex separable Hilbert space (variously called the "state space" or the "associated Hilbert space" of the system) well defined upto a complex number of norm 1 (the phase factor). In other words, the possible states are points in the projectivization of a Hilbert space. The exact nature of this Hilbert space is dependent on the system; for example, the state space for position and momentum states is the space of square-integrable functions, while the state space for the spin of a single proton is just the product of two complex planes. Each observable is represented by a densely defined Hermitian (or self-adjoint) linear operator acting on the state space. Each eigenstate of an observable corresponds to an eigenvector of the operator, and the associated eigenvalue corresponds to the value of the observable in that eigenstate. If the operator's spectrum is discrete, the observable can only attain those discrete eigenvalues.
The time evolution of a quantum state is described by the Schrödinger equation, in which the Hamiltonian, the operator corresponding to the total energy of the system, generates time evolution. The inner product between two state vectors is a complex number known as a probability amplitude. During a measurement, the probability that a system collapses from a given initial state to a particular eigenstate is given by the square of the absolute value of the probability amplitudes between the initial and final states. The possible results of a measurement are the eigenvalues of the operator - which explains the choice of Hermitian operators, for which all the eigenvalues are real. We can find the probability distribution of an observable in a given state by computing the spectral decomposition of the corresponding operator. Heisenberg's uncertainty principle is represented by the statement that the operators corresponding to certain observables do not commute.
The Schrödinger equation acts on the entire probability amplitude, not merely its absolute value. Whereas the absolute value of the probability amplitude encodes information about probabilities, its phase encodes information about the interference between quantum states. This gives rise to the wave-like behavior of quantum states. It turns out that analytic solutions of Schrödinger's equation are only available for a small number of model Hamiltonians, of which the quantum harmonic oscillator, the particle in a box, the hydrogen-molecular ion and the hydrogen atom are the most important representatives. Even the helium atom, which contains just one more electron than hydrogen, defies all attempts at a fully analytic treatment. There exist several techniques for generating approximate solutions. For instance, in the method known as perturbation theory one uses the analytic results for a simple quantum mechanical model to generate results for a more complicated model related to the simple model by, for example, the addition of a weak potential energy. Another method is the "semi-classical equation of motion" approach, which applies to systems for which quantum mechanics produces weak deviations from classical behavior. The deviations can be calculated based on the classical motion. This approach is important for the field of quantum chaos. An alternative formulation of quantum mechanics is Feynman's path integral formulation, in which a quantum-mechanical amplitude is considered as a sum over histories between initial and final states; this is the quantum-mechanical counterpart of action principles in classical mechanics.
Interactions with other scientific theories
The fundamental rules of quantum mechanics are very broad. They state that the state space of a system is a Hilbert space and the observables are Hermitian operators acting on that space, but do not tell us which Hilbert space or which operators. These must be chosen appropriately in order to obtain a quantitative description of a quantum system. An important guide for making these choices is the correspondence principle, which states that the predictions of quantum mechanics reduce to those of classical physics when a system moves to higher energies or equivalently, larger quantum numbers . This "high energy" limit is known as the classical or correspondence limit. One can therefore start from an established classical model of a particular system, and attempt to guess the underlying quantum model that gives rise to the classical model in the correspondence limit. When quantum mechanics was originally formulated, it was applied to models whose correspondence limit was non-relativistic classical mechanics. For instance, the well-known model of the quantum harmonic oscillator uses an explicitly non-relativistic expression for the kinetic energy of the oscillator, and is thus a quantum version of the classical harmonic oscillator.
Early attempts to merge quantum mechanics with special relativity involved the replacement of the Schrödinger equation with a covariant equation such as the Klein-Gordon equation or the Dirac equation. While these theories were successful in explaining many experimental results, they had certain unsatisfactory qualities stemming from their neglect of the relativistic creation and annihilation of particles. A fully relativistic quantum theory required the development of quantum field theory, which applies quantization to a field rather than a fixed set of particles. The first complete quantum field theory, quantum electrodynamics, provides a fully quantum description of the electromagnetic interaction. The full apparatus of quantum field theory is often unnecessary for describing electrodynamic systems. A simpler approach, one employed since the inception of quantum mechanics, is to treat charged particles as quantum mechanical objects being acted on by a classical electromagnetic field. For example, the elementary quantum model of the hydrogen atom describes the electric field of the hydrogen atom using a classical Coulomb potential. This "semi-classical" approach fails if quantum fluctuations in the electromagnetic field play an important role, such as in the emission of photons by charged particles.
Quantum field theories for the strong nuclear force and the weak nuclear force have been developed. The quantum field theory of the strong nuclear force is called quantum chromodynamics, and describes the interactions of the subnuclear particles: quarks and gluons. The weak nuclear force and the electromagnetic force were unified, in their quantized forms, into a single quantum field theory known as electroweak theory. It has proven difficult to construct quantum models of gravity, the remaining fundamental force. Semi-classical approximations are workable, and have led to predictions such as Hawking radiation. However, the formulation of a complete theory of quantum gravity is hindered by apparent incompatibilities between general relativity, the most accurate theory of gravity currently known, and some of the fundamental assumptions of quantum theory. The resolution of these incompatibilities is an area of active research, and theories such as string theory are among the possible candidates for a future theory of quantum gravity.
Quantum mechanics has had enormous success in explaining many of the features of our world. The individual behaviour of the subatomic particles that make up all forms of matter - electrons, protons, neutrons, photons and so forth - can often only be satisfactorily described using quantum mechanics. Quantum mechanics has strongly influenced string theory, a candidate for a theory of everything (see Reductionism). It is also related to statistical mechanics. Quantum mechanics is important for understanding how individual atoms combine covalently to form chemicals or molecules. The application of quantum mechanics to chemistry is known as quantum chemistry. (Relativistic) quantum mechanics can in principle mathematically describe most of chemistry. Quantum mechanics can provide quantitative insight into ionic and covalent bonding processes by explicitly showing which molecules are energetically favorable to which others, and by approximately how much. Most of the calculations performed in computational chemistry rely on quantum mechanics. Much of modern technology operates at a scale where quantum effects are significant. Examples include the laser, the transistor, the electron microscope, and magnetic resonance imaging. The study of semiconductors led to the invention of the diode and the transistor, which are indispensable for modern electronics. Researchers are currently seeking robust methods of directly manipulating quantum states. Efforts are being made to develop quantum cryptography, which will allow guaranteed secure transmission of information. A more distant goal is the development of quantum computers, which are expected to perform certain computational tasks exponentially faster than classical computers. Another active research topic is quantum teleportation, which deals with techniques to transmit quantum states over arbitrary distances.
Philosophical consequences
An interpretation of quantum mechanics is an attempt to answer the question, What exactly is quantum mechanics talking about? The question has its historical roots in the nature of quantum mechanics itself which was considered as a radical departure from previous physical theories. However, quantum mechanics has been described as "the most precisely tested and most successful theory in the history of science" (c.f. Jackiw and Kleppner, 2000.)
Since its inception, the many counter-intuitive results of quantum mechanics have provoked strong philosophical debate and many interpretations. Even fundamental issues such as Max Born's basic rules concerning probability amplitudes and probability distributions took decades to be appreciated. The Copenhagen interpretation, due largely to the Danish theoretical physicist Niels Bohr, is the interpretation of quantum mechanics most widely accepted amongst physicists. According to it, the probabilistic nature of quantum mechanics predictions cannot be explained in terms of some other deterministic theory, and does not simply reflect our limited knowledge. Quantum mechanics provides probabilistic results because the physical universe is itself probabilistic rather than deterministic.
An interpretation can be characterized by whether it satisfies certain properties, such as:
- Realism
- Completeness
- Local realism
- Determinism
To explain these properties, we need to be more explicit about the kind of picture an interpretation provides. To that end we will regard an interpretation as a correspondence between the elements of the mathematical formalism M and the elements of an interpreting structure I, where:
- The mathematical formalism consists of the Hilbert space machinery of ket-vectors, self-adjoint operators acting on the space of ket-vectors, unitary time dependence of ket-vectors and measurement operations. In this context a measurement operation can be regarded as a transformation which carries a ket-vector into a probability distribution on ket-vectors. See also quantum operations for a formalization of this concept.
- The interpreting structure includes states, transitions between states, measurement operations and possibly information about spatial extension of these elements. A measurement operation here refers to an operation which returns a value and results in a possible system state change. Spatial information, for instance would be exhibited by states represented as functions on configuration space. The transitions may be non-deterministic or probabilistic or there may be infinitely many states. However, the critical assumption of an interpretation is that the elements of I are regarded as physically real.
In this sense, an interpretation can be regarded as a semantics for the mathematical formalism.
In particular, the bare instrumentalist view of quantum mechanics outlined in the previous section is not an interpretation at all since it makes no claims about elements of physical reality. The current use in physics of "completeness" and "realism" is often considered to have originated in the paper (Einstein et al., 1935) which proposed the EPR paradox. In that paper the authors proposed the concept "element of reality" and "completeness" of a physical theory. Though they did not define "element of reality", they did provide a sufficient characterization for it, namely a quantity whose value can be predicted with certainty before measuring it or disturbing it in any way. EPR define a "complete physical theory" as one in which every element of physical reality is accounted for by the theory. In the semantic view of interpretation, an interpretation of a theory is complete if every element of the interpreting structure is accounted for by the mathematical formalism. Realism is a property of each one of the elements of the mathematical formalism; any such element is real if it corresponds to something in the interpreting structure. For instance, in some interpretations of quantum mechanics (such as the many-worlds interpretation) the ket vector associated to the system state is assumed to correspond to an element of physical reality, while in others it does not.
Determinism is a property characterizing state changes due to the passage of time, namely that the state at an instant of time in the future is a function of the state at the present (see time evolution). It may not always be clear whether a particular interpreting structure is deterministic or not, precisely because there may not be a clear choice for a time parameter. Moreover, a given theory may have two interpretations, one of which is deterministic, and the other not.
Local realism has two parts:
- The value returned by a measurement corresponds to the value of some function on the state space. Stated in another way, this value is an element of reality;
- The effects of measurement have a propagation speed not exceeding some universal bound (e.g., the speed of light). In order for this to make sense, measurement operations must be spatially localized in the interpreting structure.
A precise formulation of local realism in terms of a local hidden variable theory was proposed by John Bell. Bell's theorem and its experimental verification restrict the kinds of properties a quantum theory can have. For instance, Bell's theorem implies quantum mechanics cannot satisfy local realism.
Albert Einstein, himself one of the founders of quantum theory, disliked this loss of determinism in measurement. He held that there should be a local hidden variable theory underlying quantum mechanics and consequently the present theory was incomplete. He produced a series of objections to the theory, the most famous of which has become known as the EPR paradox. John Bell showed that the EPR paradox led to experimentally testable differences between quantum mechanics and local hidden variable theories. Experiments have been taken as confirming that quantum mechanics is correct and the real world cannot be described in terms of such hidden variables. "Loopholes" in the experiments, however, mean that the question is still not quite settled.
The Everett many-worlds interpretation, formulated in 1956, holds that all the possibilities described by quantum theory simultaneously occur in a "multiverse" composed of mostly independent parallel universes. This is not accomplished by introducing some new axiom to quantum mechanics, but on the contrary by removing the axiom of the collapse of the wave packet: All the possible consistent states of the measured system and the measuring apparatus (including the observer) are present in a real physical (not just formally mathematical, as in other interpretations) quantum superposition. (Such a superposition of consistent state combinations of different systems is called an entangled state.) While the multiverse is deterministic, we perceive non-deterministic behavior governed by probabilities, because we can observe only the universe, i.e. the consistent state contribution to the mentioned superposition, we inhabit. Everett's interpretation is perfectly consistent with John Bell's experiments and makes them intuitively understandable. However, according to the theory of quantum decoherence, the parallel universes will never be accessible for us, making them physically meaningless. This inaccessiblity can be understood as follows: once a measurement is done, the measured system becomes entangled with both the physicist who measured it and a huge number of other particles, some of which are photons flying away towards the other end of the universe; in order to prove that the wave function did not collapse one would have to bring all these particles back and measure them again, together with the system that was measured originally. This is completely impractical, but even if one can theoretically do this, it would destroy any evidence that the original measurement took place (including the physicist's memory).
Consistent histories
The consistent histories generalizes the conventional Copenhagen interpretation and attempts to provide a natural interpretation of quantum cosmology. The theory is based on a consistency criterion that then allows the history of a system to be described so that the probabilities for each history obey the additive rules of classical probability while being consistent with the Schrödinger equation. According to this interpretation, the purpose of a quantum-mechanical theory is to predict probabilities of various alternative histories.
Many worlds
The many-worlds interpretation (or MWI) is an interpretation of quantum mechanics that rejects the non-deterministic and irreversible wavefunction collapse associated with measurement in the Copenhagen interpretation in favor of a description in terms of quantum entanglement and reversible time evolution of states. The phenomena associated with measurement are explained by decoherence which occurs when states interact with the environment. As result of the decoherence the world-lines of macroscopic objects repeatedly split into mutally unobservable, branching histories -- distinct universes within a greater multiverse.
The Copenhagen Interpretation
The Copenhagen interpretation is an interpretation of quantum mechanics formulated by Niels Bohr and Werner Heisenberg while collaborating in Copenhagen around 1927. Bohr and Heisenberg extended the probabilistic interpretation of the wavefunction, proposed by Max Born. The Copenhagen interpretation rejects questions like "where was the particle before I measured its position" as meaningless. The act of measurement causes an instantaneous "collapse of the wave function". This means that the measurement process randomly picks out exactly one of the many possibilities allowed for by the state's wave function, and the wave function instantaneously changes to reflect that pick.
Quantum Logic
Quantum logic can be regarded as a kind of propositional logic suitable for understanding the apparent anomalies regarding quantum measurement, most notably those concerning composition of measurement operations of complementary variables. This research area and its name originated in the 1936 paper by Garrett Birkhoff and John von Neumann, who attempted to reconcile some of the apparent inconsistencies of classical boolean logic with the facts related to measurement and observation in quantum mechanics.
The Bohm interpretation
The Bohm interpretation of quantum mechanics is an interpretation postulated by David Bohm in which the existence of a non-local universal wavefunction allows distant particles to interact instantaneously. The interpretation generalizes Louis de Broglie's pilot wave theory from 1927, which posits that both wave and particle are real. The wave function 'guides' the motion of the particle, and evolves according to the Schrödinger equation. The interpretation assumes a single, nonsplitting universe (unlike the Everett many-worlds interpretation) and is deterministic (unlike the Copenhagen interpretation). It says the state of the universe evolves smoothly through time, without the collapsing of wavefunctions when a measurement occurs, as in the Copenhagen interpretation. However, it does this by assuming a number of hidden variables, namely the positions of all the particles in the universe, which, like probability amplitudes in other interpretations, can never be measured directly.
Transactional interpretation
The transactional interpretation of quantum mechanics (TIQM) by John Cramer is an unusual interpretation of quantum mechanics that describes quantum interactions in terms of a standing wave formed by retarded (forward-in-time) and advanced (backward-in-time) waves. The author argues that it avoids the philosophical problems with the Copenhagen interpretation and the role of the observer, and resolves various quantum paradoxes.
Consciousness causes collapse
Consciousness causes collapse is the speculative theory that observation by a conscious observer is responsible for the wavefunction collapse. It is an attempt to solve the Wigner's friend paradox by simply stating that collapse occurs at the first "conscious" observer. Supporters claim this is not a revival of substance dualism, since (in a ramification of this view) consciousness and objects are entangled and cannot be considered as distinct. The consciousness causes collapse theory can be considered as a speculative appendage to almost any interpretation of quantum mechanics and most physicists reject it as unverifiable and introducing unnecessary elements into physics.
Relational Quantum Mechanics
The essential idea behind Relational Quantum Mechanics, following the precedent of Special Relativity, is that different observers may give different accounts of the same series of events: for example, to one observer at a given point in time, a system may be in a single, "collapsed" eigenstate, while to another observer at the same time, it may be in a superposition of two or more states. Consequently, if quantum mechanics is to be a complete theory, Relational Quantum Mechanics argues that the notion of "state" describes not the observed system itself, but the relationship, or correlation, between the system and its observer(s). The state vector of conventional quantum mechanics becomes a description of the correlation of some degrees of freedom in the observer, with respect to the observed system. However, it is held by Relational Quantum Mechanics that this applies to all physical objects, whether or not they are conscious or macroscopic. Any "measurement event" is seen simply as an ordinary physical interaction, an establishment of the sort of correlation discussed above. Thus the physical content of the theory is to do not with objects themselves, but the relations between them [1]. For more information, see Rovelli (1996).
Modal Interpretations of Quantum Theory
Modal interpretations of Quantum mechanics were first conceived of in 1972 by B. van Fraassen, in his paper "A formal approach to the philosophy of science". However, this term now is used to describe a larger set of models that grew out of this approach. The Stanford Encyclopedia of Philosophy describes several versions:
- The Copenhagen Variant
- Kochen-Dieks-Healey Interpretations
- Motivating Early Modal Interpretations, based on the work of R. Clifton, M. Dickson and J. Bub.
Explanation of quantum mechanics enigmas
The Spacetime Model can be considered as the continuation of Eintein's works. Instead of limiting spacetime to General Relativity (mass and gravity), the author has extended it to all elements of the universe. The result is that spacetime explains with logic and consistency 53 enigmas of Quantum Mechanics: wave-particle duality, elementary particles (quarks and leptons), mass, gravity, charge, antimatter, Standard Model.... It unifies the three basic forces (electroweak, stong nuclear and gravity) in two generic forces. Contrary to other theories, the Spacetime Model requires only four dimensions: x, y, z and t. To get additional information concerning this new theory, please download the free 220 pages document at www.spacetime-model.com.
Founding experiments
- Thomas Young's double-slit experiment demonstrating the wave nature of light (c1805)
- Henri Becquerel discovers radioactivity (1896)
- Joseph John Thomson's cathode ray tube experiments (discovers the electron and its negative charge) (1897)
- The study of black body radiation between 1850 and 1900, which could not be explained without quantum concepts.
- The photoelectric effect: Einstein explained this in 1905 (and later received a Nobel prize for it) using the concept of photons, particles of light with quantized energy
- Robert Millikan's oil-drop experiment, which showed that electric charge occurs as quanta (whole units), (1909)
- Ernest Rutherford's gold foil experiment disproved the plum pudding model of the atom which suggested that the mass and positive charge of the atom are almost uniformly distributed. (1911)
- Professor Walter Ernhart-Plank's Proton Collapse experiment disproved the Rutherford model and temporarily cast doubt on the distribution of protons throughout an atom.
- Otto Stern and Walther Gerlach conduct the Stern-Gerlach experiment, which demonstrates the quantized nature of particle spin (1920)
- Clinton Davisson and Lester Germer demonstrate the wave nature of the electron [2] in the Electron diffraction experiment (1927)
- Clyde L. Cowan and Frederick Reines confirm the existence of the neutrino in the neutrino experiment (1955)
- Claus Jönsson`s double-slit experiment with electrons (1961)
Research and Development
- Marine Algae Using Quantum Mechanics Principles for Light Harvesting - Experimental results suggest that the energy of absorbed light resides in two places at once — a quantum superposition state, or coherence – and such a state lies at the heart of quantum mechanical theory. (The Green Optimistic; Feb. 4, 2010)
- One small step for a man, one giant leap for teleportation - According to LiveScience, the university's Joint Quantum Institute for the first time was able to teleport information between two separate atoms across a distance of a meter - about one step for an adult, using "entanglement". (CNet News; Jan. 26, 2009)
External articles and references
- citations
- ^ The Davisson-Germer experiment, which demonstrates the wave nature of the electron
- ^ http://plato.stanford.edu/entries/qm-relational/
- Books
- P. A. M. Dirac, The Principles of Quantum Mechanics (1930) -- the beginning chapters provide a very clear and comprehensible introduction
- David Griffiths, Introduction to Quantum Mechanics, Prentice Hall, 1995. ISBN 0-13-111892-7
- Richard P. Feynman, Robert B. Leighton and Matthew Sands (1965). The Feynman Lectures on Physics, Addison-Wesley. Richard Feynman's original lectures (given at CALTECH in early 1962) can also be downloaded as an MP3 file from www.audible.com[1]
- Hugh Everett, Relative State Formulation of Quantum Mechanics, Reviews of Modern Physics vol 29, (1957) pp 454-462.
- Bryce DeWitt, R. Neill Graham, eds, The Many-Worlds Interpretation of Quantum Mechanics, Princeton Series in Physics, Princeton University Press (1973), ISBN 0-691-08131-X
- Albert Messiah, Quantum Mechanics, English translation by G. M. Temmer of Mécanique Quantique, 1966, John Wiley and Sons, vol. I, chapter IV, section III.
- Richard P. Feynman, QED: The Strange Theory of Light and Matter -- a popular science book about quantum mechanics and quantum field theory that contains many enlightening insights that are interesting for the expert as well
- Marvin Chester, Primer of Quantum Mechanics, 1987, John Wiley, N.Y. ISBN 0-486-42878-8
- Hagen Kleinert, Path Integrals in Quantum Mechanics, Statistics, Polymer Physics, and Financial Markets, 3th edition, World Scientific (Singapore, 2004)(also available online here)
- George Mackey (2004). The mathematical foundations of quantum mechanics. Dover Publications. ISBN 0-486-43517-2.
- Griffiths, David J. (2004). Introduction to Quantum Mechanics (2nd ed.). Prentice Hall. ISBN 0-13-805326-X.
- Omnes, Roland (1999). Understanding Quantum Mechanics. Princeton University Press. ISBN 0-691-00435-8.
- J. von Neumann, Mathematical Foundations of Quantum Mechanics, Princeton University Press, 1955.
- H. Weyl, The Theory of Groups and Quantum Mechanics, Dover Publications 1950.
- Max Jammer, "The Conceptual Development of Quantum Mechanics" (McGraw Hill Book Co., 1966)
- Gunther Ludwig, "Wave Mechanics" (Pergamon Press, 1968) ISBN 08-203204-1
- General
- J J O'Connor and E F Robertson, A history of quantum mechanics www-history.mcs.st-andrews.ac.uk
- James Higgo A Lazy Layman's Guide to Quantum Physics higgo.com 1999
- Introduction to Quantum Theory at Quantiki, cam.qubit.org. Content is available under GNU Free Documentation License.
- Wikipedia contributors, Wikipedia: The Free Encyclopedia. Wikimedia Foundation.
- Quantum Physics Made Relatively Simple: three video lectures by Hans Bethe
- Decoherence by Erich Joos
- Course material
- MIT OpenCourseWare: Chemistry. See 5.61, 5.73, and 5.74
- MIT OpenCourseWare: Physics. See 8.04, 8.05, and 8.06.
- Imperial College Quantum Mechanics Course to Download
- A set of downloadable tutorials on Quantum Mechanics, Imperial College
- Spark Notes - Quantum Physics
- FAQs
- Many-worlds or relative-state interpretation
- Measurement in Quantum mechanics
- A short FAQ on quantum resonances
- Media
- Everything you wanted to know about the quantum world — archive of articles from New Scientist magazine.
- Quantum Physics Research From ScienceDaily
- {{{last}}}, {{{first}}}, "Quantum Trickery: Testing Einstein's Strangest Theory". The New York Times, December 27, 2005 (Accessed: {{{accessdate}}})
- The mystery of the wave-particle duality
- Explanation of 53 enigmas of Quantum Physics. The PDF document available on this link is also edited by AC42 ISBN 97829531234-0-1.
- Philosophy
- Quantum Mechanics (Stanford Encyclopedia of Philosophy)
- David Mermin on the future directions of physics
- "Quantum Physics Quackery" by Victor Stenger, Skeptical Inquirer (January/February 1997).
- Crank Dot Net's quantum physics page — "cranks, crackpots, kooks & loons on the net"
- Hinduism & Quantum Physics


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STERLING, Va. (WUSA9) -- Loudoun County fire officials say a house fire on December 2 was accidental.
The fire, which destroyed a single-family home on Dairy Lane in Broad Run, was caused by an electrical short in the attic, officials said.
Fire and rescue personnel from Sterling, Ashburn, Moorefield, Leesburg and Fairfax responded to the scene.
Fire officials say they found the home fully involved. Since the home was located in a non-hydrant area, rural water supply was established.
The damage is an estimated $350,000. The family of four who lived in the home was not inside during the fire.
No one was injured.


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Smartphone technology has undergone a progressive change over the past few years, and it has enhanced and even altered the way we spend our 24 hours. In this digital era, we often work or communicate on different screens, right from tablets, PCs to smartphones. We not only use these multiple screens for getting in touch with one another but also use it as a medium to keep us updated on current news, latest trends in fashion, music, advertisements for new products, etc. Even while watching TV, smartphones continue to remain the first screen and hence the accessibility of mobile devices remains strong. According to Milward Brown, smartphones are the most used screens globally and with the consumption of content on the smartphone on the rise, many companies and brands see it as a leveraging tool to market their products to the end consumer in an effective manner.
With the smartphone explosion, advertising agencies have also started developing campaigns that reach out to the smartphone users. Today, marketers are looking at working towards creating a 360-degree marketing plan which comprises all the relevant touch points to reach the consumers. Advertisers have to now think beyond ad banners and start leveraging interactive and engaging mobile advertising formats; this could mean building ad experiences for smartphones or more effectively monetising mobile content to the consumer.
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For every marketer, location is a significant quotient in reaching out to the target market. With the availability of various location based mobile applications and the large presence of social media on smartphones, marketing to the end-consumer has become easier. But the inevitable question always remains as to how to reach the end-customer on a real-time basis, as it is a crucial factor in increasing consumer engagement and improving customer experience. There are various channels for


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I can generally agree with what you said here. I do not think it negates my point though. My point was not to argue for anyone using a specific bar height, but that they should consider using something similar to what they use on their road bike. They just might find that higher bars may not allow more comfort and may actually cause more back and butt discomfort.
On the distribution of weight... I'd argue that a large portion of the rider's weight should be supported by their legs and sitting upright does not promote that in my experience.
I concede that there is a very broad range of what works for a broad range of individuals and that I am probably pretty close to an extreme end of that continuum.


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MORGANTOWN - After giving up 45 or more points in each of the first three Big 12 Conference games, the West Virginia defensive unit knows the time of making excuses has passed.
''You can't make excuses just because of a new scheme and new coaches,'' defensive back Darwin Cook said. ''We still have to go out there as players and make plays. You can't just blame it on new coaches and new schemes. You just have to make plays.''
That much-maligned unit will again be tested as No. 4 Kansas State, 5-0 overall and 2-0 in the Big 12, comes to Morgantown for a 7 p.m. Saturday contest that will be televised across the nation on Fox. WVU comes into the game ranked 17th with a 5-1 overall record and 2-1 in the conference.
Article Photos
Darwin Cook (25) and the WVU defense says no excuses are good enough for their poor play.
West Virginia coach Dana Holgorsen has said the front seven of his defense has played well, particularly in shutting down opposing running games. That ability should help against the Wildcats' power game.
''They are only snapping the ball 63 times a game, but they are scoring 40 points a game,'' Holgorsen said. ''They have big-play potential. They do it in a different way.''
Holgorsen said the biggest challenge for the Mountaineers will be stopping K-State's vaunted running attack.
''That's what I'm built for,'' linebacker Doug Rigg said. ''That's what I love to see. I'm excited for this game. I'll be ready to play this weekend.''
The Wildcats are led by quarterback Collin Klein, a dual-threat. He averages about 100 yards a game running, but has talented speedsters on the wings waiting for the pass play to be called.
''Then when they throw the ball, we need to be making plays down field,'' Holgorsen said. ''We haven't done a very good job of making plays down field, and that is a little bit of an understatement.''
''A lot of times, (Klein) will look like he's running the ball, then he'll pretend to run the ball but throw it deep,'' Rigg said. ''He has the arm to complete it. We can't just assume it's going to be a run and give up the receivers deep.''
Cook said many of the deep plays surrendered by the secondary this season have not been because of confusion, but a lack of mental effort.
''We have to get our calls known around us,'' he said. ''You have to communicate that to everybody. We just have to get better on that part - communication.''


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How can Hopkins have so much hate thrown at him. Many people change teams (& jobs even) because it seems right at the time (I know I did the same) Ever since the world champs started there have been riders who should not have been there but somehow conjured up support. Back in the 50s Gilera would give a local a ride in his home GP in the hope he could help keep the opposition away from the points & therefore help their chosen 1
Anyone read Rossi's pleas for the performance level of "private" bikes to be raised to enable them to have a chance???


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Pennoni awarded oceanfront survey contract in NJ
Pennoni Associates, an Engineering News Record Top 100 engineering, design, and consulting firm with an office in Milton, has been awarded a contract by the City of Long Branch, N.J., to carry out an oceanfront survey of its beaches, boardwalk, and easternmost roadways. The survey will include the beachfront bluff that was damaged by Hurricane Sandy in 2012.
This survey will use airborne and ground-based Lidar as well as state-of-the-art high-definition laser scanning. After assessing the conditions of the bluff, which helps support the boardwalk, the survey will assist the City of Long Branch in choosing a new design for it. Pennoni will also survey the five arterial roads that extend from Ocean Avenue to Ocean Boulevard to see how much damage they suffered from the storm. The roads include Brighton Avenue, West End Avenue, Cottage Place, South Bath Avenue, and North Bath Avenue.
Pennoni offers support to communities affected by natural disasters through the restorative and recovery processes. The beaches along the Atlantic Coast are continually under siege by Mother Nature. While many enjoy days spent at the shore, few realize how much effort goes into maintaining this ever-changing landscape.
To assist communities in responding to the increased frequency and intensity of storm events, Pennoni has developed a decision support tool for improving coastal resilience. Pennoni's Coastal Resilience Toolkit provides the basic tools necessary to measure a community's preparedness for coastal storms and provide guidance on how to plan and respond before, during and after a major flooding event.
For more information on Pennoni go to www.pennoni.com.


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If you love dice games and math games, Yamslam will be right up your alley. You're rolling the dice in order to collect the corresponding chips before your oppponents do. You roll in the tin container...that looks like it's a travel game for the Ocean Eleven crowd. The Vegas/poker style look of this one attracted some of our older testers. A good game for building math skills.
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Are you one of the few that were lucky enough to nab the elusive Nexus 4 by Google? If you do possess Android's hard to attain device and are into modding/rooting, then finding the perfect ROM can be hard, and maybe even overwhelming at times. RasBean Jelly is a custom AOSP ROM made by the developer Rascarlo and has been around since the Galaxy Nexus days when it was called Rascream (back when Ice Cream Sandwich was the latest ROM). If you're an avid ROM flasher, then you're well aware that a handful of the ones you flash tend to have bugs and other problems that you'll frequently encounter. While that's expected, that's one thing that I don't particularly enjoy about flashing custom ROM's.
With RasBean, I have never encountered a bug or any problems in any build that I've tried, even in my ICS Galaxy Nexus days. RasBean is an AOSP based ROM that's dedicated to speed and overall stability. While Rascarlo does include several additional features to the ROM, he makes sure to clean the ROM of necessary codes and "bloat." Thus, if you're a huge CM or AOKP fan, then this ROM may not be for you as it doesn't have the dozens upon dozens of added features that those two ROM's tend to have. But if you're looking for a super fast ROM with no bugs, then RBJ just might be for you! Hit the break to find out more.


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my 2004 saturn ion makes a very LOUD rumbling noise when driving. The front wheel hub on the driver's side has been replaced but it still makes this unbearable noise, it sounds like it's coming from the front driver's side. What else could be the promblem?
by jce in Macon, GA on August 25, 2009


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– Kanye West now has two sex tapes floating around, one of which might feature Kim Kardashian. [The Superficial]
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– Newborn panda found tragically dead at National Zoo. [Jezebel]
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– The best frozen moments from the 2012 Emmy Awards. [Vulture]
– Helen Mirren and The Queen screenwriter Peter Morgan reunite to bring Elizabeth II to the stage. [Anglophenia]


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Hi folks,
Before we begin, please note: I don't have much experience as a sysadmin, so please excuse me if I'll ask newbie questions.
OS & Details:
- CentOS 6x64
- Virtualized: yes, on OpenVZ
- ZCS: Release 7.1.4_GA_2555.RHEL6_64_20120105094542 CentOSUNKNOWN_64 FOSS edition.
- DNS - EXTERNAL, hosted on a cPanel server.
- ZCS installed after this tutorial (obviously I've changed the IPs properly)
Explanation: I've created a separate VPS in order to test Zimbra, named "zimbra.myhost.tld". In cPanel I've created a A entry and pointed it to the test VPS IP. Also I've reversed the IP in .arpa (on the cPanel server, obviously).
- the installation was stopping at "ldap...". This solution solved the problem, the installation finished
- when executing /opt/zimbra/libexec/zmsetup.pl I receive a lot of:
ANDERROR: service.FAILURE (system failure: unable to lookup server by name: zimbra.webhipo.ro message: [LDAP: error code 80 - internal error]) (cause: javax.naming.NamingException [LDAP: error code 80 - internal error])]
ANDCould not create the Java virtual machine.
- when trying to login I receive the following error:/opt/zimbra/bin/zmshutil: line 39: Error: command not found
Can you please give me a hand? Thanks a lot!system failure: unable to lookup account via query: (&(|(email@example.com. ro)(email@example.com))(obje ctclass=zimbraAccount)) message: [LDAP: error code 80 - internal error]


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In the past 3 weeks:
Printable View
In the past 3 weeks:
To put this in perspective, less people on the American side died in WW2... in a period of 3 years.
29.5 million per month. 7 million per week.
unequivocal proof that libertarians are out of their fucking minds:
pathetic internet
so... does that count people who re-watched it on different computers?
if you watch it, refresh, and watch it again, it gets another tick
so that could be the same 5 people watching it on loop... O_O
also you dont have to watch to the end, just start it and watch I think 20% of the vid for it to count as a view... so I bet most of those ppl didnt make it to the end
Keke Le Cat; Destroyer of Dreams.


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Inyo National Forest
Contact Information
Inyo National Forest
351 Pacu Lane
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Inyo National Forest contains over 800,000 acres of wilderness, in nine wilderness areas. Wilderness areas include the Hoover, Ansel Adams, Owens River Headwaters, John Muir, Golden Trout, South Sierra, Boundary Peak, White Mountains and Inyo Mountains.
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"A wilderness, in contrast with those areas where man and his works dominate the landscape, is hereby recognized as an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain...land retaining its primeval character and influence...protected and managed so as to preserve its natural conditions..."
Wilderness Act of 1964 - Section 2(c)
Areas for Backpacking at Wilderness Areas
Areas for Horse Riding at Wilderness Areas
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Quick Links
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To the editor:
The future of America is now in the hands of its youngest voters.
Their task on Nov. 6 will not be easy. They must now discern between two candidates who repeatedly accuse each other of lying.
One of them really does have less commitment to the truth; and, as is often the case with purveyors of false promises, he is now accusing the other of the same.
In promising a handout to all distressed segments of the population, he has laid the groundwork for a society that will be almost totally dependent on its central government. The ultimate cost will be in individual pride and freedom.
What those distressed citizens really need is a job. The American dream has always been working one�s way out of difficult circumstances.
If the candidate promising everyone a personal bonus gets his way, this country will almost certainly turn into a socialist welfare state. Try to spot some of those false promises and then vote for the other guy. He will undoubtedly be more capitalistic in his viewpoints.
While America is now in more danger than ever before, its young men and women are fully up to the challenge.
John Poole
Emerald Isle
Location, ST | website.com


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Premchand (1880-1936) is not an author most of us pick up eagerly to read. This is a fall-out from having to study him in school, as part of Hindi literature. Dhanno said the other day, while watching part of 'Bhagwan Dada', "Why are they talking like characters from a Premchand story?" and she did not mean it as a compliment.
I began re-reading Premchand again, only a couple of years ago. Yes, his characters do tend to pontificate, about their ideology and beliefs, rather a lot, but I think that was pretty standard practice in most novel writing in those days.
What had me hooked first was a scene in 'Nirmala'. Nirmala is a young girl, married off to a much older man, with 2 sons. Despite her understandable dislike of this relationship, she goes into the marriage determined to fulfill her duties. She likes little children and makes friends with her husband's children, but her husband's widowed sister, who lives with them, keeps indicating that she is a step-mother. At one point, Nirmala, as a mother, wants to scold and slap one of the boys, but holds back because she becomes conscious that she will be blamed for being a step-mother. It is a small moment, but leads to so many misunderstandings, and a growing distance between the family members that ends in break-ups, death and loneliness.
This scene also resonated with me, because I remember once, Teja scolding Dhanno, outside a restaurant. She was 6 or 7, we had barely started our relationship, she was being stubborn, and refusing to come off a toy horse, much after her stipulated share of rides. A close friend said to Teja, "It's amazing how you scold her. I would be so frightened to do it, scared to upset her, scared of what she would think of me." But Teja never treated Dhanno with kid gloves, and that had her accepting him without question.
Premchand also goes into great detail with each one of his characterizations. No one is black or white. At the most heroic moments, people have other thoughts racing in their minds, they are brave, but also petty, mean but also forthright, generous but also misguided, selfish and selfless, and everyone changes from time to time, growing, learning, affecting and being affected by not only each other's actions, but also each other's thoughts. The internal workings of Premchand's characters is fascinating, particularly for any aspiring writer. I would recommend reading Premchand, only if to study development of character.
Through the other novels, it is this unfailing logic of events rising from small decisions, good and bad, small cowardices and misdemeanors, small resolutions and courage, that bind a whole world together. This fits into my own perspective of how life is, each one of us, each act, each thought inextricably linked with the other.
The novels I have read are, apart from 'Nirmala', 'Premashram', 'Karmabhoomi' and 'Gaban'. 'Premashram' and 'Karmabhoomi' are the more difficult to get through, because they are also top-heavy with political ideology. 'Gaban' is quite an interesting tale of a weak, young man, fascinated by money, and all it can buy, and a wife who is naive enough not to question where the money is coming from, the chaos that unfolds because of this character flaw. However it leads to greater maturity and happiness for all in the end.
Another aspect of Premchand's novels, is the women despite their traditional roles, are very strong, and often come to their senses much faster than the men.
I see in my own self, the continuous flow of thoughts. In my actions, when I am hurt, miserable, angry, envious, I often get carried away in the moment. When I am friendly, confident, bright, positive, I can see myself from the outside. And I can also hear a litany of thoughts in my mind, quite contrary to my outward behavior. This is a matter of my own temperament. And I guess all enlightenment comes through one or the other, to lose oneself in the moment, and to observe every moment, or rather a balance of both.
While you are at it, my review of Premashram.
Banno, I read Premchand in school too! You are right, I didn't appreciate him much then. He seemed to hit me over the head with moral lessons (and I didn't want moral lessons. Besides, no one I knew spoke HIndi like that. Thankfully, in my misbegotten youth, I eventually learnt to appreciate him. Thank you for the review and the memories.
Dustedoff, I couldn't have liked Premchand, not with my Hindi teacher, who was a very good one by the way, but oh, gosh, the accent! She had half of us rolling in the aisles with splits. I learnt to appreciate him by accident. I was at my aunt's house for the summer hols and was bored out of my head because there was nothing to do, and I found an English translation of a collection of his short stories that belonged to my grandfather. So, in the age, where I read everything, including the wrapping on mungphali, I read it and was totally engrossed by the characters. So, of course, I had to hunt down and read the originals. Nirmala was shown on DD? I don't remember watching it. Perhaps they didn't show it down south.😦
Banno.. I am a Premchand addict.. have been reading his stories since I learnt to read, and continue to this day.. almost every evening. So to me, the familiarity is overwhelming, a way of life. There is no way that I can analyse his work or characters, but I definitely prefer his stories to his novels. I think I read his books because they take me back to Allahabad.. to my childhood home and serve as an escape mechanism. Well.. this is as nonsensical a comment as can be… but I'll post all the same.
Well.. I think I know why I posted that comment.. I trusted you to make sense out of it Whatever happened to our plans of catching up?


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Panic by Lauren Oliver Recommended Ages: 13+ Heather and Dodge are two sides of the same coin, just two kids looking to rectify the problems of their unpleasant home lives in the middle of Carp, population 12,000. And when Panic starts ups again, an annual summer contest for graduating high school seniors that pushes their fears and limits to the brink, both of them realize an opportunity to get themselves out of their respective troubles. ... Read More »
Tag Archives: friendship
Book Review: It's Kind of a Funny Story by Ned Vizzini
It's Kind of a Funny Story by Ned Vizzini Recommended Ages: 13+ At the risk of sounding too much like a trailer warning for the newest episode of Law & Order, I would like to preface this discussion by noting that the themes of It's Kind of a Funny Story may be of a more sensitive nature for some people out there. Craig Gilner is a fairly typical American teenager living in New York trying ... Read More »
Book Review: Aliens on Vacation by Clete Barrett Smith
Aliens on Vacation by Clete Barrett Smith Recommended Ages: 12+ "Intergalactic Bed & Breakfast" is the name of the series, as well as the place young David "Scrub" Elliott finds himself visiting over the summer between sixth and seventh grade. It isn't that Scrub is into science fiction, so much. His main interest is basketball. He would rather be back in Florida, trading insane dares with his best friend and training for the all-star team. ... Read More »
Book Review: Untold by Sarah Rees Brennan
Untold by Sarah Rees Brennan Recommended Ages: 13+ In Book 2 of "The Lynburn Legacy," a dark ultimatum looms over the outwardly charming town of Sorry-in-the-Vale. The evil sorcerer Rob Lynburn means to return the town to its old ways, in which the sorcerous few held power over the non-magical many—an arrangement whereby good weather and prosperous fortunes were given in exchange for blood sacrifice. Rob and his sorcerers demand a victim—a human victim, mind ... Read More »
Book Review: The Journal of Curious Letters by James Dashner
The Journal of Curious Letters by James Dashner Recommended Ages: 11+ Atticus Higginbottom, Tick to his friends, is a 13-year-old science geek who gets bullied at school, trips over his own feet, and plays champion-level chess. Few people would guess that such a boy would have the makings of a hero who might one day save the world. Somebody seems to have guessed, however. Somebody calling himself M. G. (short for Master George) begins sending ... Read More »
Book Review: The Throne of Fire by Rick Riordan
The Throne of Fire by Rick Riordan Recommended Ages: 12+ In Book 2 of the "Kane Chronicles," the Texas-based author of the "Tres Navarre" mysteries cleverly uses hilarious, romantic, magical, and thrill-packed entertainment to educate young adults about ancient Egyptian mythology. He's very sneaky that way. But we're not surprised, since he did the same thing with Greek mythology in the "Percy Jackson and the Olympians" series. Ditto Roman mythology in the "Heroes of Olympus" ... Read More »
Book Review: The Last Dragonslayer by Jasper Fforde
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Book Review: Brisingr by Christopher Paolini
Brisingr by Christopher Paolini Recommended Ages: 13+ Many things discouraged me from reading the third book of the Inheritance Cycle. There was the backlash against my mixed review of Book 2, Eldest—almost, but not quite, the harshest feedback I have received. There was the disappointment of the film based on Book 1, Eragon—a hint that there would be less pressure from Fandom in General to stay on top of this series. And finally, there was ... Read More »
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