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Researchers release design for stable, scalable quantum processor
 Coupling Si:P spin qubits to electric fields

The phosphorus donor in silicon comprises an electron spin S = 1/2 with gyromagnetic ratio γ e = 27.97 GHz T−1 and basis states \(\left| \downarrow \right\rangle \), \(\left| \uparrow \right\rangle \), and a nuclear spin I = 1/2 with gyromagnetic ratio γ n = 17.23 MHz T−1 and basis states \(\left| \Downarrow \right\rangle ,\left| \Uparrow \right\rangle \). The electron interacts with the nucleus through the hyperfine coupling A ≈ 117 MHz. When placed in a large magnetic field B 0 (\({\gamma _ + }{B_0} \gg A\), with γ + = γ e + γ n ), the eigenstates of the system are the separable tensor products of the basis states, i.e., \(\left| { \downarrow \Uparrow } \right\rangle \), \(\left| { \downarrow \Downarrow } \right\rangle \), \(\left| { \uparrow \Downarrow } \right\rangle \), \(\left| { \uparrow \Uparrow } \right\rangle \) (Fig. 1c). The electron and the nucleus can be operated as single qubits by applying oscillating magnetic fields resonant with any of the transitions frequencies between eigenstates that differ by the flipping of one of the spins, e.g., \(\left| { \downarrow \Uparrow } \right\rangle \) ↔ \(\left| { \uparrow \Uparrow } \right\rangle \) for the electron qubit, etc. (Fig. 1c).

Fig. 1 Coupling donor spin qubits to electric fields via hyperfine modulation. a Qubit unit cell, in which the electron interface state, |i〉, is coupled to the donor-bound state, |d〉, by a tunnel rate V t . The solid black line represents the conduction band profile along z. b Bloch sphere of a flip-flop spin qubit coupled to a vertical electric field E z via the hyperfine interaction A. Electron-nuclear singlet and triplet states are denoted by \(S = \left( {\left| { \downarrow \Uparrow } \right\rangle - \left| { \uparrow \Downarrow } \right\rangle } \right){\rm{/}}\sqrt 2 \) and \({T_0} = \left( {\left| { \downarrow \Uparrow } \right\rangle + \left| { \uparrow \Downarrow } \right\rangle } \right){\rm{/}}\sqrt 2 \). c Si:P electron-nuclear spin levels, showing standard electron spin resonance (ESR) and nuclear magnetic resonance (NMR) transitions, together with hyperfine-enabled EDSR. d Atomistic tight-binding simulations72 (dots) of the electron-nucleus hyperfine interaction, for a z d = 15.2 nm deep donor, as a function of vertical electric field. The solid line is a fit using the simplified two-level Hamiltonian \({{\cal H}_{{\rm{orb}}}} + {\cal H}_A^{{\rm{orb}}}\), which yields V t = 9.3 GHz (see Supplementary Note 1). The insets show the electron ground-state wavefunction, \(\left| g \right\rangle \), in the region within dashed lines in a, for three different vertical electric fields. Scale bar is 10 nm Full size image

We envisage a device where a shallow 31P donor is embedded in an isotopically enriched 28Si crystal at a depth z d from the interface with a thin SiO 2 layer (Fig. 1a). The orbital wavefunction ψ of the donor-bound electron can be controlled by a vertical electric field E z applied by a metal gate on top. It changes from a bulk-like donor state at low electric fields to an interface-like state at high fields33, 34 (insets in Fig. 1d). The hyperfine interaction A(E z ), proportional to the square amplitude of the electron wavefunction at the donor site |ψ(0, 0, z d )|2, changes accordingly from the bulk value A ≈ 117 MHz to A ≈ 0 when the electron is fully displaced to the interface (Fig. 1d). Shifting the electron wavefunction also results in the creation of an electric dipole μ e = ed, where e is the electron charge and d is the separation between the mean positions of the donor-bound and interface-bound wavefunctions (d ≲ z d , see Supplementary Note 1). The induced electric dipole μ e has been largely overlooked in the past, but plays a crucial role in this proposal.

The key idea is to define a new qubit, called henceforth the flip-flop qubit, described in the subspace spanned by the states \(\left| { \downarrow \Uparrow } \right\rangle \), \(\left| { \uparrow \Downarrow } \right\rangle \). Transitions between these basis states cannot be induced by magnetic resonance, because there is no change in the z-component of the total angular momentum. However, the hyperfine interaction, A S ⋅ I, is a transverse term in the flip-flop basis, since its eigenstates are \(S = \left( {\left| { \downarrow \Uparrow } \right\rangle - \left| { \uparrow \Downarrow } \right\rangle } \right){\rm{/}}\sqrt 2 \) and \({T_0} = \left( {\left| { \downarrow \Uparrow } \right\rangle + \left| { \uparrow \Downarrow } \right\rangle } \right){\rm{/}}\sqrt 2 \) (Fig. 1b). Therefore, electrically modulating A(E z ) at the frequency

$${\epsilon _{{\rm{ff}}}}(A) = \sqrt {{{\left( {{\gamma _ + }{B_0}} \right)}^2} + {{\left[ {A\left( {{E_{\rm{z}}}} \right)} \right]}^2}} ,$$ (1)

corresponding to the flip-flop qubit energy splitting, causes an electric dipole spin resonance (EDSR) transition between the \(\left| { \downarrow \Uparrow } \right\rangle \), \(\left| { \uparrow \Downarrow } \right\rangle \) basis states35, 36 (Fig. 1c). This transition is faster at the “ionization point”, where the electron is shared halfway between donor and interface, since A(E z ) can vary strongly upon the application of a small voltage on the top gate.

Electrical noise and relaxation

Since the qubit operation is based upon the use of electric fields, a natural concern is the fragility of the qubit states in the presence of electric noise. Below we show that there are special bias points that render the flip-flop qubit operation highly robust against noise.

A quantum-mechanical description of the system is obtained by treating also the electron position as a two-level system (effectively a charge qubit; see Supplementary Note 1 for a justification of this two-level approximation), where the vertical position of the electron is represented by a Pauli σ z operator, with eigenvectors |d 〉, for the electron at the donor, and |i 〉 at the interface (Fig. 1a, d). The simplified orbital Hamiltonian reads (in units of Hz):

$${{\cal H}_{{\rm{orb}}}} = \frac{{{V_{\rm{t}}}{\sigma _{\rm{x}}} - \left[ {e\left( {{E_{\rm{z}}} - E_{\rm{z}}^0} \right)d{\rm{/}}h} \right]{\sigma _{\rm{z}}}}}{2},$$ (2)

where V t is the tunnel coupling between the donor and the interface potential wells, \(E_{z}^0\) is the vertical electric field at the ionization point, and h is the Planck constant. The electron ground |g 〉 and excited |e 〉 orbital eigenstates depend on E z (Fig. 1d) and have an energy difference given by:

$${\epsilon _{\rm{o}}} = \sqrt {{{\left( {{V_{\rm{t}}}} \right)}^2} + {{\left[ {e\left( {{E_{z}} - E_{z}^0} \right)d{\rm{/}}h} \right]}^2}}$$ (3)

At the ionization point, the energy difference between eigenstates \(\left| e \right\rangle = \left( {\left| d \right\rangle + \left| i \right\rangle } \right){\rm{/}}\sqrt 2 \) and \(\left| g \right\rangle = \left( {\left| d \right\rangle - \left| i \right\rangle } \right)/\sqrt 2 \) is minimum and equal to V t (Fig. 2a), and therefore first-order insensitive to electric noise, ∂\({\epsilon _o}\)/∂E z = 0. This bias point is referred to as the “charge qubit sweet spot”37 (CQSS—Fig. 2a).

Fig. 2 Robustness to electric noise. a Charge, \({\epsilon _o}\), and flip-flop, \({\epsilon _{{\rm{ff}}}}\), qubit transition frequencies as a function of vertical electric field E z , for B 0 = 0.4 T, A = 117 MHz, d = 15 nm, Δ γ = −0.2% and V t = 11.44 GHz. The inset shows the level diagram of flip-flop states coupled to charge states. CT stands for “clock transition” and CQSS for “charge qubit sweet spot”. b Estimated flip-flop qubit dephasing rate, assuming electric field noise \(E_{z{\rm{,rms}}}^{{\rm{noise}}} = 100\) V m−1. c E z -dependence of flip-flop precession frequency for the three indicated tunnel coupling values. d Flip-flop qubit relaxation rate, with arrows indicating the adiabatic path used for z-gates. e Flip-flop qubit dephasing rate due to E z noise and relaxation, at second-order CTs for each B 0 . f Device structure to tune the tunnel coupling V t of the charge qubit. Scale bar is 30 nm. g V t as a function of right gate voltage, calculated using a finite element Poisson solver (Synopsis TCAD) and atomistic tight biding (NEMO-3D)72. The insets illustrate the NEMO-3D wavefunctions inside dashed region in f, for three right gate voltages V r = −1, −0.35 and −0.27 V. The left gate voltage is V l = −0.5 V for all the simulations, and the top gate is biased such that the position of the electron is in between the donor and interface. Scale bar is 20 nm. The donor is assumed to be z d = 9.2 nm below the Si/SiO 2 interface Full size image

Conversely, the bare flip-flop qubit energy is expected to depend strongly on E z , through the combined effect of the hyperfine interaction A (Eq. 1) and the orbital dependence of the electron gyromagnetic ratio, γ e . Indeed, the gyromagnetic ratio of an electron confined at a Si/SiO 2 interface can differ from that of a donor-bound electron by a relative amount Δ γ up to 0.7%38. Therefore, the Zeeman terms in the Hamiltonian must include a dependence of the electron Zeeman splitting on its orbital position, i.e., the charge qubit σ z operator:

$${\cal H}_{{B_0}}^{{\rm{orb}}} = {\gamma _{\rm{e}}}{B_0}\left[ {1 + \left( {\frac{{1 + {\sigma _{z}}}}{2}} \right){\Delta_\gamma }} \right]{S_{\rm{z}}} - {\gamma _{\rm{n}}}{B_0}{I_{z}}.$$ (4)

We can also write the hyperfine coupling as an operator that depends on the charge qubit state:

$${\cal H}_A^{{\rm{orb}}} = A\left( {\frac{{1 - {\sigma _{\rm{z}}}}}{2}} \right){\bf{S}} \cdot {\bf{I}}$$ (5)

Indeed, this simple two-level approximation, shown as a black line in Fig. 1d, reproduces the full tight-biding simulations (yellow dots).

The overall flip-flop qubit transition frequency as a function of E z becomes:

$${\epsilon _{{\rm{ff}}}}\left( {A,{\gamma _{\rm{e}}}} \right) = \sqrt {{{\left[ {{\gamma _{\rm{e}}}\left( {{E_{\rm{z}}}} \right) + {\gamma _{\rm{n}}}} \right]}^2}{B_0}^2 + {{\left[ {A\left( {{E_{\rm{z}}}} \right)} \right]}^2}} ,$$ (6)

shown in Fig. 2a (dashed line), where we assumed Δ γ = −0.2%38. \({\epsilon _{{\rm{ff}}}}\)(A, γ e ) shows a steep slope around the ionization point, mostly caused by the E z -dependence of γ e (the dependence on A is less significant because \({\gamma _ + }{B_0} \gg A\)). Therefore, while \({E_{z}} \approx E_{z}^0\) is the fastest operation point for the flip-flop qubit driven by a resonant modulation of A, one might expect it to be the most prone to qubit dephasing from charge and gate noise, through the influence of E z on γ e .

However, computing instead the full flip-flop qubit Hamiltonian,

$${{\cal H}_{{\rm{ff}}}} = {\cal H}_{{B_0}}^{{\rm{orb}}} + {\cal H}_A^{{\rm{orb}}} + {{\cal H}_{{\rm{orb}}}},$$ (7)

reveals that the qubit transition frequency has an extra bend around the ionization point (Fig. 2a, thick yellow line). This comes from Eq. (5), which provides a transverse coupling g so between the flip-flop and charge qubits (inset in Fig. 2a):

$${g_{{\rm{so}}}} = \frac{A}{4}\frac{{{V_{\rm{t}}}}}{{{\epsilon _{\rm{o}}}}}$$ (8)

As a result, the electron orbit dispersively shifts the flip-flop qubit by, to second order:

$${D_{{\rm{orb}}}}\left( {{E_{z}}} \right) = \frac{{{{\left[ {{g_{{\rm{so}}}}\left( {{E_{z}}} \right)} \right]}^2}}}{{{\delta _{{\rm{so}}}}\left( {{E_{z}}} \right)}},$$ (9)

where δ so = \({\epsilon _o}\) − \({\epsilon _{{\rm{ff}}}}\), reducing the flip-flop qubit frequency to:

$${\epsilon _{{\rm{ff}}}}\left( {A,{\gamma _{\rm{e}}},{D_{{\rm{orb}}}}} \right) = {\epsilon _{{\rm{ff}}}}\left( {A,{\gamma _{\rm{e}}}} \right) - {D_{{\rm{orb}}}}\left( {{E_{z}}} \right),$$ (10)

D orb (E z ) is largest around \({E_{z}} \approx E_{z}^0\), since δ so is lowest (i.e., the charge qubit frequency comes closest to the flip-flop qubit, Fig. 2a) and g so is highest. Equation (10) (thin black line in Fig. 2a) agrees with full numerical simulations of the Hamiltonian in Eq. (7).

Such a dispersive shift stabilizes the flip-flop precession frequency against noise. To quantify that, we assume a quasi-static electric field noise with 100 V m−1 r.m.s. amplitude along the donor-dot direction (z-axis in Fig. 1a). This noise is equivalent to a 1.5 μeV charge detuning noise for d = 15 nm, consistent with experimentally observed values in similar silicon devices39,40,41—see Supplementary Note 3. The estimated—see Methods section—dephasing rates can be as low as \(1{\rm{/}}T_2^ * \approx 3\) kHz (Fig. 2b), comparable to the ones due to magnetic noise (\(1/T_2^ * \approx 1\) kHz in 28Si nanostructures7). This can be understood from Fig. 2c, which shows the qubit precession frequency dependence on E z , for three different values of V t . For small detunings δ so , i.e., V t close to \({\epsilon _{{\rm{ff}}}}\), the dispersive shift around the ionization point is strong, yielding two first-order “clock transitions” (CT), where ∂\({\epsilon _{{\rm{ff}}}}\)/∂E z = 0 where the dephasing rate is reduced. By increasing V t , the two first-order points merge into a single one in which both the first and second derivatives vanish, yielding the slowest qubit dephasing.

Another source of errors could come from relaxation via coupling to phonons. This is not an issue for bulk donors, where electron spin relaxation time is \({T_{1,{\rm{s}}}} \gg 1\) s18. However, due to the particular valley composition of the flip-flop qubit near the ionization point, its relaxation rate 1/T 1,ff due to charge-phonon coupling is enhanced42. We estimate it by noting that, if \({\delta _{{\rm{so}}}} \gg {g_{{\rm{so}}}}\), 1/T 1,ff is equal to the amount of charge excited state in the flip-flop eigenstates43 times the charge relaxation rate42:

$$1{\rm{/}}{T_{1,{\rm{ff}}}} = {\left( {{g_{{\rm{so}}}}{\rm{/}}{\delta _{{\rm{so}}}}} \right)^2}{\rm{/}}{T_{1,{\rm{o}}}},$$ (11)

$$1{\rm{/}}{T_{1,{\rm{o}}}} = \Theta {\epsilon _{\rm{o}}}{V_{\rm{t}}}^2,$$ (12)

where T 1,o is the charge qubit lifetime and Θ ≈ 2.37 × 10−24 s2 is determined by the silicon crystal properties42. Therefore, as can be seen from Fig. 2d, the higher the detuning δ so , the slower the relaxation. In particular, at the second-order CT, the qubit dephasing can be limited by relaxation, \(1{\rm{/}}T_2^* = 1{\rm{/}}2{T_1} \approx {10^4}\) Hz. This limitation can be overcome by reducing B 0 (Fig. 2e).

Tuning a flip-flop qubit into a clock transition requires the ability to tune the tunnel coupling V t . The latter is difficult to control at the fabrication stage, given its exponential dependence on donor depth, together with oscillations at the atomic scale44 arising from a similar valley interference effect as the one afflicting the exchange interaction16. Indeed, ion-implanting a donor at z d ≈ 15 nm below the interface happens with a vertical uncertainty of order ±10nm45, resulting in more than two orders of magnitude uncertainty in V t 44. Therefore, it is crucial to implement a method to tune V t in situ. A possible solution is to displace the location of the interface wavefunction laterally, which in turn modifies the overlap between the donor and interface wavefunctions and therefore V t . This can be done by adding two gates on either side of the top gate, which pulls the donor electron to the interface (Fig. 2f), in such a way that a relative voltage between the gates can modify the interface lateral potential landscape. This gate stack is identical to the well-established scheme for the confinement of single electrons in Si quantum dots10. This technique allows V t to be tuned by at least wo orders of magnitude (Fig. 2g), therefore circumventing the uncertainty in donor depth and V t arising from ion-implantation.

Adiabatic phase control

The presence of slow dephasing regions is important to control the qubit phase with high fidelity. In our quantum processor, idle qubits are decoupled from electric fields by fully displacing the electron either to the interface or to the donor. Performing quantum operations on the qubit requires displacing the electrons close to the ionization point, which in turn changes its precession frequency (Fig. 2a). As a result, the accumulated phase must be corrected after quantum operations. This is optimally done by moving the electron to the second-order clock transition, therefore minimizing dephasing errors. At this point, the flip-flop qubit phase precesses \({\rm{\∼}}{\Delta _\gamma }{\gamma _{\rm{e}}}{B_0}{\rm{/}}2 - {D_{{\rm{orb}}}}\) faster than its idle point, and therefore any phase correction in a 2π period can be applied within tens of ns. The dephasing rate at the CT, on the order of a few kHz, would cause very small errors (<10−4). However, while moving the electron from the interface toward the donor, the flip-flop qubit goes through regions of fast dephasing (Fig. 2b), and therefore this operation has to be performed as quickly as possible. It also has to be slow enough as to avoid erros due to non-adiabaticity, which include, e.g., leakage to unwanted high-energy states. These errors depend on the adiabatic factor K, which quantifies the fractional rate of change of the system’s eigenstates (the higher the value of K, the more adiabatic and slower is the process—see Methods section).

In Fig. 3a, we plot the time dynamics of an initial state \(\left| g \right\rangle \otimes \left( {\left| { \downarrow \Uparrow } \right\rangle + \left| { \uparrow \Downarrow } \right\rangle } \right){\rm{/}}\sqrt 2 \) while sweeping E z adiabatically (K = 50) to move the electron from the interface to the second-order CT and back, in order to realize a π z-gate. The initial adiabatic set-up part consists of a fast sweep (0.8 ns), allowed by the large charge qubit splitting when \({E_{\rm{z}}} \gg E_{\rm{z}}^0\), followed by a slower sweep (3.5 ns), limited by the proximity of excited charge states to the flip-flop qubit when \({E_{\rm{z}}} \approx E_{\rm{z}}^0\). The electron then remains at the CT for 60 ns, before adiabatically moving back to the interface. During the total 69 ns, the flip-flop qubit phase is shifted by π, with adiabatic errors, averaged over a set of initial flip-flop states—see Methods section—around 10−4. These errors can be controlled with the factor K, which determines the set-up time (see Fig. 3b).

Fig. 3 High-fidelity adiabatic z-gates. a Time-evolution of an adiabatic (K = 50) π z-gate on state \(\left| g \right\rangle \otimes \left( {\left| { \downarrow \Uparrow } \right\rangle + \left| { \uparrow \Downarrow } \right\rangle } \right){\rm{/}}\sqrt 2 \), showing applied electric field and flip-flop/charge states. Outer brackets denote the expectation value of an operator. \(\sigma _{z}^{{\rm{ff}}} = \left| { \uparrow \Downarrow } \right\rangle \left\langle { \uparrow \Downarrow } \right| - \left| { \downarrow \Uparrow } \right\rangle \left\langle { \downarrow \Uparrow } \right|\) and \(\sigma _x^{{\rm{ff}}} = \left| { + _x^{{\rm{ff}}}} \right\rangle \left\langle { + _x^{{\rm{ff}}}} \right| - \left| { - _x^{{\rm{ff}}}} \right\rangle \left\langle { - _x^{{\rm{ff}}}} \right|\), where \(\left| { + _x^{{\rm{ff}}}} \right\rangle = \left( {\left| { \uparrow \Downarrow } \right\rangle + {\rm{exp}}\left( { - i2\pi \epsilon _{{\rm{ff}}}^{t = 0}} \right)\left| { \downarrow \Uparrow } \right\rangle } \right){\rm{/}}\sqrt 2 \) and \(\left| { - _x^{{\rm{ff}}}} \right\rangle = \left( {\left| { \uparrow \Downarrow } \right\rangle + {\rm{exp}}\left( { - i2\pi \epsilon _{{\rm{ff}}}^{t = 0} - i\pi } \right)\left| { \downarrow \Uparrow } \right\rangle } \right){\rm{/}}\sqrt 2 \). Fast oscillations between the charge and flip-flop states are due to small deviations from perfect adiabaticity. b π z-gate leakage error for different adiabatic set-up times, which are set by the factor K. c π z-gate error due to quasi-static E z noise, at the second-order CT at B 0 = 0.4 T, for different noise amplitudes and adiabatic set-up times Full size image

Quasi-static E z noise can increase errors, due to dephasing (Fig. 3c). At realistic noise levels (100 V m−1), the gate error rate is found to be <10−4. Similar error levels arise due to relaxation, which remains below 3 × 104 Hz (Fig. 2d).

Note that the presence of clock transitions does not affect the ability to use E ac to resonantly drive the qubit, since the transverse term A(E z ) still responds fully to the electric field (this is similar to the case of magnetic clock transitions, e.g,. in Si:Bi46).

Electric drive of the flip-flop qubit

We now explain how high-fidelity one-qubit x(y)-gates can be achieved via electric drive of the flip-flop qubit. The fastest one-qubit gates are obtained when the electron is around the ionization point, where ∂A/∂E z is maximum (Fig. 1d). A vertical oscillating electric field of amplitude E ac is applied (Fig. 4a) in resonance with the flip-flop qubit, i.e., ν E = \({\epsilon _{{\rm{ff}}}}\). A large detuning \({\delta _{{\rm{so}}}} \gg {g_{{\rm{so}}}}\) (Fig. 4b) ensures the least amount of the charge excited state \(\left| e \right\rangle \) in the qubit eigenstates, minimizing qubit relaxation via charge-phonon coupling. The flip-flop qubit is still driven, via a second-order process, at a rate (half-Rabi frequency):

$$g_{\rm{E}}^{{\rm{ff}}} = \frac{{{g_{{\rm{so}}}}{g_{\rm{E}}}}}{2}\left( {\frac{1}{{{\delta _{{\rm{so}}}}}} + \frac{1}{{{\delta _{\rm{E}}}}}} \right),$$ (13)

where δ E = ν E − \({\epsilon _o}\) and g E is the driven electric coupling rate between the two charge eigenstates:

$${g_{\rm{E}}} = \frac{{e{E_{{\rm{ac}}}}d}}{{4h}}\frac{{{V_{\rm{t}}}}}{{{\epsilon _{\rm{o}}}}},$$ (14)

where E ac is the amplitude of a sinusoidal drive. Equation (13) provides another explanation of why the fastest one-qubit gates are obtained when the electron is at the ionization point: δ so and δ E are minimum (\({\epsilon _o}\) is minimum), and g so and g E are maximum (Eqs. (8) and (14)).

Fig. 4 High-fidelity electrically driven adiabatic x(y)-gates. a Spatial representation and b level diagram, for electrical drive of a flip-flop qubit, showing partially ionized electron wavefunction and spin arrows. c Time-dependent adiabatic drive amplitude and qubit dynamics of a π/2 x-gate, for K = 30, B 0 = 0.4 T, \({E_{\rm{z}}} = E_{\rm{z}}^0,\) and V t = 11.5 GHz. Bottom plot shows flip-flop z state, \(\left\langle {\sigma _{z}^{{ff}}} \right\rangle \), electron position, 〈σ z 〉, and charge qubit state, \(\left\langle {\left| e \right\rangle \left\langle e \right| - \left| g \right\rangle \left\langle g \right|} \right\rangle \). For the same parameters, d shows the averaged drive power and gate time, and e the error rates for different V t . To estimate the drive power, we assumed a 50 Ω line in which a 1 μV AC voltage produces a 10 V m−1 AC vertical electric field. f Estimated flip-flop qubit π/2 x-gate error due to quasi-static noise with amplitude \(E_{z{\rm{,rms}}}^{{\rm{noise}}} = 100\) V m−1. g Dependence of gate error rate on the electric noise r.m.s. amplitude and adiabatic factor K (which sets the gate time) Full size image

The electrical drive can cause some excitation of the charge qubit. It is therefore convenient to turn E ac on/off adiabatically to make sure the charge is de-excited at the end of the gate. Figure 4c shows the E ac time evolution needed for a π/2 x-gate, where we have assumed an adiabatic factor K = 30, sufficient for leakage errors <10−3. E ac increases steadily until a π/4 rotation is completed, after which E ac is gradually switched off to achieve an adiabatic π/2 x-gate. An average 4% excitation of the charge qubit causes a ~4 × 104 Hz relaxation rate of the encoded quantum state (Eq. 12), or error levels close to 10−3.

We then investigate how the total π/2 x-gate errors depend on the biasing of the electron wavefunction. At the ionization point, \(E_{z} = E_{z}^0\), error levels close to 10−3 are found over a wide range of V t (Fig. 4e). The K = 30 choice ensures adiabatic errors <10−3 with an oscillatory character typical of adiabatic processes47. At small V t (and therefore small detuning δ so ), the qubit eigenstates contain a substantial amount of charge, causing more errors due to charge-phonon relaxation. Increasing the detuning δ E with larger V t allows for a faster adiabatic sweep and higher powers (Fig. 4d), yielding shorter gate times and therefore less errors due to quasi-static noise. Still, the incident power is at least three orders of magnitude lower than the one needed to drive donor electron spin qubits, at the same Rabi frequency, with oscillating magnetic fields7, 19.

As Fig. 4f shows, low error rates are still available away from the ionization point, even though best values are found at \({E_{z}} = E_{z}^0\). This is because our gate times are so fast that dephasing, and therefore CTs, do not play a crucial role. Instead, quasi-static E z noise cause errors mainly by modulating the driving strength \(g_{\rm{E}}^{{\rm{ff}}}\), causing “gate time jitter”. Indeed, the gate time is sensitive to the orbital transition frequency \({\epsilon _o}\) (Eq. 13), and therefore gate errors are minimized close to the charge qubit sweet spot (CQSS), where ∂\({\epsilon _o}\)/∂E z = 0 (Fig. 2a).

Finally, as Fig. 4g shows, lower quasi-static E z noise can cause less errors, provided that the adiabatic factor K is increased, to reduce leakage errors, up to an optimum value where gate times are still fast as to keep noise errors low. Relaxation errors could also be reduced by reducing B 0 (recall Fig. 2e).

A number of other noise sources, including high frequency charge noise, Johnson-Nyquist, and evanescent-wave Johnson noise48 (EWJN) also affect qubits that are sensitive to electric fields. However, as we discuss in Supplementary Note 3, the corresponding error rates are much lower than the ones already previously mentioned—see all estimated error levels in Table 1.

Table 1 Error rates of x(y)-gates from different noise sources as discussed in Supplementary Note 3 Full size table

Two-qubit coupling via electric dipole interaction

We now present the method to couple donor spins that lies at the heart of our scalable quantum processor. It exploits the electric dipole that naturally arises when a donor-electron wavefunction is biased to the ionization point (Fig. 5a), due to the fact that a negative charge has been partly displaced away from the positive 31P nucleus. The electric field produced by this induced dipole in turn, modifies the energy of a nearby donor which is also biased at the ionization point, resulting in a long-range coupling between the two.

Fig. 5 Robust electric dipole-dipole interactions between two distant flip-flop qubits. a Device scheme for coupling qubits, showing dipole field lines, E dip , produced by the dipole on the left. b Level diagram for two-qubit coupling via electric dipole-dipole interaction. c Lowest molecular eigenstates for the two charge qubits inside dashed rectangle in b. The eigenenergy shift equals D dd = (δ so,2 − δ so,1 )\((\sqrt {1+[2g_{dd}/({\delta _{{\rm{so}},2}}-{\delta _{{\rm{so}},1}})]^2}-1)/2 \). The eigenstate coefficients are \(\beta = \theta {\rm{/}}\sqrt {{\theta ^2} + 1} \) and \(\alpha = \phi {\rm{/}}\sqrt {{\phi ^{\rm{2}}}{\rm{ + 1}}} \), with \(\theta ,\phi = \left[ {\left( {{\delta _{{\rm{so}},2}} - {\delta _{{\rm{so}},1}}} \right) \pm \sqrt {{{\left( {{\delta _{{\rm{so}},2}} - {\delta _{{\rm{so}},1}}} \right)}^2} + {{\left( {2{g_{{\rm{dd}}}}} \right)}^2}} } \right]{\rm{/}}\left( {2{g_{{\rm{dd}}}}} \right)\). Effective coupling between two flip-flop qubits as a function of V t,1 = V t,2 = V t , interdistance r (d) and electric field E z,1 = E z,2 = E z (e). The arrows in e represent the adiabatic path followed for two-qubit gates. \(E_{z}^{{\rm{0}},2{\rm{q}}}\) is the ionization point in the presence of a second qubit, \(E_{z}^{{\rm{0,2q}}} = E_{z}^0 - 2{g_{{\rm{dd}}}}h{\rm{/}}\left( {2e{d_{\rm{i}}}} \right)\) Full size image

The interaction energy between two distant dipoles, μ 1 and μ 2 , oriented perpendicularly to their separation, r, is49 \({V_{{\rm{dip}}}} = {\mu _1}{\mu _2}{\rm{/}}\left( {4\pi {\varepsilon _{\rm{r}}}{\varepsilon _0}{r^3}} \right)\), where ε 0 is the vacuum permittivity and \(\epsilon \) r the material’s dielectric constant (ε r = 11.7 in silicon). The electric dipole of each donor-interface state is μ i = ed i (1 + σ z,i )/2, implying that the dipole-dipole interaction Hamiltonian is:

$${{\cal H}_{{\rm{dip}}}} = {V_{{\rm{dd}}}}\left( {{\sigma _{{\rm{z}},1}}{\sigma _{{\rm{z}},2}} + {\sigma _{{\rm{z}},1}} + {\sigma _{{\rm{z}},2}}} \right)$$ (15)

$${V_{{\rm{dd}}}} = \frac{1}{{16\pi {\varepsilon _0}{\varepsilon _{\rm{r}}}h}}\frac{{{e^2}{d_1}{d_2}}}{{{r^3}}}$$ (16)

This electric dipole-dipole interaction is therefore equivalent to a small shift in the equilibrium orbital position of both electrons plus a coupling term between the charge qubits (blue dashed rectangle in Fig. 5b) equal to:

$${g_{{\rm{dd}}}} = {V_{{\rm{dd}}}}\frac{{{V_{{\rm{t}},1}}{V_{{\rm{t}},2}}}}{{{\epsilon _{{\rm{o}},1}}{\epsilon _{{\rm{o}},2}}}}$$ (17)

Note that this interaction can be stronger due to the presence of a metallic interface on top of the qubits, which enhances vertical dipoles—see Supplementary Note 2. Most importantly, since each flip-flop qubit is coupled to their electron position (Eq. 5), the electric dipole-dipole interaction provides a natural way to couple two distant flip-flop qubits.

Indeed, the effective coupling rate between two flip-flop qubits at the ionization point, Fig. 5d, exceeds 10 MHz around two narrow regions. These bands can be understood from the energy-level diagram shown in Fig. 5c. The two charge qubits in Fig. 5b form hybridized molecular states, which are coupled to each flip-flop qubit. The two-qubit coupling rate is maximum when in resonance with a molecular state. However, this regime induces too many relaxation errors due to resonant charge excitation. Therefore, it is best to detune the flip-flop qubits from the molecular states, while still keeping a substantial inter-qubit coupling rate, via a second-order process, equal to:

$$g_{{\rm{2q}}}^{{\rm{ff}}} = {g_{{\rm{so,1}}}}{g_{{\rm{so,2}}}}\alpha \beta \left( {\frac{1}{{{D_{{\rm{dd}}}} - {\delta _{{\rm{so}},1}}}} + \frac{1}{{{D_{{\rm{dd}}}} + {\delta _{{\rm{so,2}}}}}}} \right),$$ (18)

where D dd is the charge eigenenergies shift and α, β the eigenstates coefficients—see Fig. 5c caption.

Two-qubit gates start with both electrons at the interface, where qubits are decoupled since the electric dipoles and the hyperfine interactions are first-order insensitive to vertical electric fields. Indeed, from Eq. (18), \(g_{{\rm{2q}}}^{{\rm{ff}}}\) is negligible since g so vanishes and δ so diverges. The electrons are then simultaneously and adiabatically displaced to the ionization point for a time necessary for an \(\sqrt {i{\rm{SWAP}}} \) gate, before returning to the interface. In Fig. 6a, we show the dynamics of a two-qubit gate performed with an adiabatic factor K = 30, following the trajectory shown in Fig. 5e. Similarly to one-qubit z-gates, the electron is first displaced in a fast time scale (~0.3 ns) set by the charge qubit parameters (\({\epsilon _0}\) and V t ), followed by a slower sweep (~19 ns) set by the spin-charge coupling parameters (δ so and g so ), until it reaches the ionization point. The electron remains still for a short time before the whole process is then reversed. In the end, a \(\sqrt {i{\rm{SWAP}}} \) gate is performed. While some amount of charge is excited during the process, it goes back to its ground state, \(\left| {gg} \right\rangle \), with an adiabatic error around 10−3.

Fig. 6 High-fidelity adiabatic \(\sqrt {i{\rm{SWAP}}} \) gates between two distant flip-flop qubits. a Time evolution of an adiabatic \(\sqrt {i{\rm{SWAP}}} \) gate, for K = 30, r = 180 nm, B 0 = 0.4 T, and V t = 11.58 GHz. b Optimized \(\sqrt {i{\rm{SWAP}}} \) gate error, gate time, and adiabatic factor K. c Optimized error rate arising from quasi-static E z -noise, for different noise amplitudes and adiabatic factor K (which sets the gate time) Full size image

We quantify the two-qubit gate fidelity in presence of the most deleterious noise types for our qubits, namely quasi-static E z noise and charge-phonon relaxation. For this, we observe that the optimal gate fidelities are achieved when \({E_{z}}\left( {{\tau _{\sqrt {i{\rm{SWAP}}} }}{\rm{/}}2} \right) \approx E_{z}^0\). Similarly to one-qubit x-gates, this happens because \(\sqrt {i{\rm{SWAP}}} \) gates are sensitive to gate time jitter, and therefore errors are minimized at the CQSS, where \(g_{{\rm{2q}}}^{{\rm{ff}}}\) is robust against E z noise to first order—recall Fig. 5e and Eq. (18). An optimization algorithm finds the best adiabatic factor K that minimizes errors due to E z noise for each value of V t,1 = V t,2 = V t . The result is shown in Fig. 6b. Smaller detunings δ so (small V t ) result in shorter gate times, which in turn reduces errors from quasi-static noise. However, this also implies a larger admixture of charge in the qubit eigenstates, which slightly increases relaxation errors. The lowest error rates, ~3 × 10−3 are found at small detunings, V t − \({\epsilon _{{\rm{ff}}}}\) − g dd ≈ 100 MHz (V t ≈ 11.59 GHz). At even smaller detunings, the two-qubit coupling rate becomes too fast, requiring faster adiabatic sweeps to avoid over-rotation (lower K, Fig. 6b) and generating more leakage errors. The gate errors remain within 10−3 − 10−2 for a wide range of V t . Finally, we estimate in Fig. 6c how noise errors depend on the noise amplitude and adiabatic factor K, which sets the gate time.

Our proposed two-qubit gates are not only well protected against noise, but also robust against donor misplacement. Variations in r, d 1 , and d 2 mainly cause variations in the charge qubits coupling g dd , therefore simply changing the energy separation between molecular charge states (Fig. 5c). However, the coupling \(g_{{\rm{2q}}}^{{\rm{ff}}}\) between the flip-flop qubits can be kept essentially constant by simply readjusting V t , using, e.g., the method described in Fig. 2f, g. Figure 5d shows that one can keep a constant value of, e.g., \(g_{{\rm{2q}}}^{{\rm{ff}}} = 1\) MHz for any inter-donor spacing between 180 and 500 nm, by adjusting V t between 11.3 and 11.8 GHz. In other words, since the flip-flop qubit coupling is mediated by a tunable interaction with their respective charge qubits, the inter-qubit interaction does not need to decay with r 3, as one would otherwise get when the dipole interaction couples the qubits directly26, 31. Therefore, two-qubit operations can be turned on between pairs of qubits separated by many sites in a two-dimensional array. This tunable long-range connectivity can be exploited to great advantage in large-scale quantum processors50. The large tolerance in g dd also accommodates very well the donor depth uncertainties inherent to ion implantation45, given the linear dependence of \(g_{{\rm{2q}}}^{{\rm{ff}}}\) on d i (Eqs. (16) and (17)).

We conclude that our scheme provides a dramatic reduction in the fabrication complexity, especially compared to schemes that require placing a gate between a pair of tightly spaced donors, such as the Kane’s proposal15, which requires r ≈ 15 nm separation between two 31P nuclear spins. Note that, by relocating the problem of valley oscillations from the exchange interaction15 to the tunnel coupling, we have effectively provided a way in which the delicate parameter can now be tuned using a much simpler gate geometry.

Scaling up using circuit quantum electrodynamics

In order to reach the long-term goal of a large-scale quantum processor, wiring up the control and read-out lines for each individual qubit is not trivial, given the high density in typical spin qubit architectures51. Recent solutions include cross-wiring using multilayer lithography26 or floating gate electrodes inspired by dynamic random access memory systems52. In both cases, using flip-flop qubits with long-distance interactions would result in widely spaced donors and loose fabrication tolerances. In addition, since flip-flop qubits are coupled via electric fields, they could be spaced further apart by using electrical mediators. These include floating metal gates53 or even microwave resonators. Indeed, the use of electric dipole transitions allows a natural integration of donor-based spin qubits into a circuit-quantum electrodynamics architecture43, 54,55,56 (see Fig. 7c for a possible device layout).

Fig. 7 Silicon hybrid quantum processor. a Figures of merit summarizing the speed and error rates of different gate schemes presented in this paper, assuming realistic noise sources. b Level diagram for distant flip-flop qubit coupling via a microwave resonator showing photon number states and off-resonant charge states. c Device scheme for coupling qubits via a photonic link. Distant donors, placed next to the resonator center line and biased to their ionization point, are subject to the vacuum electric field E vac of a shared microwave resonator. d Schematic view of a large-scale quantum processor based upon 31P donors in Si, operated and coupled through the use of an induced electric dipole. Idle qubits have electrons at the interface, leaving the 31P nucleus in the ultra-coherent ionized state. Electrons are partially shifted toward the donor for quantum operations. The sketch shows a possible architecture where a cluster of qubits is locally coupled via the electric dipole, and a subgroup thereof is further coupled to another cluster through interaction with a shared microwave cavity (aqua). The drawing is not to scale; control lines and readout devices are not shown Full size image

A full quantum mechanical treatment yields a charge-photon coupling rate given by Eq. (14), with ν E now representing the resonator fundamental mode frequency and E ac the resonator vacuum field, E vac . Again, it is best to have the charge-excited state detuned from the flip-flop transition and resonator photon (see Fig. 7b), therefore minimizing charge excitation while retaining a second-order flip-flop photon coupling given by Eq. (13). Assuming δ so ≈ δ E ≈ 10g so ≈ 10g E , a d = 15 nm deep 31P flip-flop qubit would be coupled to photons at a \(g_{\rm{E}}^{{\rm{ff}}} \approx 3\) MHz rate. This is three orders of magnitude faster than the electron-spin coupling rate to a resonator via its magnetic vacuum field57, 58, and comparable to the coupling strength obtained by using strong magnetic field gradients59, 60, but without the need to integrate magnetic materials within a superconducting circuit. This assumes a vacuum field amplitude E vac ≈ 30 V m−1, which can be obtained by using tapered coplanar waveguide or high-inductance resonators61.

The possibility of coupling the qubits to microwave photons provides a path for dispersive qubit readout, as well as for photonic interconnects. Near-quantum limited amplifiers have recently become available to obtain excellent read-out speed and fidelities62. The resonator can also be used as a quantum bus to couple two spin qubits separated by as far as 1 cm (Fig. 7c), a distance given by the mode wavelength. Figure 7b shows the detailed energy-level diagram. To avoid losses from photon decay, the qubits should be detuned from the resonator by an amount much greater than the qubit-photon coupling rates. Assuming \(\delta _{\rm{E}}^{{\rm{ff}}} = 10g_{\rm{E}}^{{\rm{ff}}}\), where \(\delta _{\rm{E}}^{{\rm{ff}}} = {

u _{\rm{E}}} - {\epsilon _{{\rm{ff}}}}\), the effective two-qubit coupling \(g_{{\rm{2q}}}^{{\rm{ff}}} \approx {\left( {g_{\rm{E}}^{{\rm{ff}}}} \right)^2}{\rm{/}}\delta _{\rm{E}}^{{\rm{ff}}} \approx 0.3\) MHz yields a \(\sqrt {i{\rm{SWAP}}} \) gate that takes only 0.4 μs.

Output: American and Australian researchers have published a paper in Nature outlining a design for a scalable, silicon quantum processor using electrical interactions to couple and integrate two-qubits logic gates into expandable arrays. The "flip-flop qubits" are made up of two phosphorus qubits coupled using donor electron interactions that have been extended over longer than normal distances (>150 nm) by microwave resonators. The team claims that the arrangement is much more fault- and noise-tolerant than previous designs and can be fabricated using existing silicon chip technology.


Instruction: create a high quality summary of the given input

Input:
This care center is combining child and senior care — and the results are beautiful!
 The Bethlehem Intergenerational Center has a unique approach to senior and child care: combine them!

The center in Grand Rapids, Michigan, is home to day care and senior care facilities, and when these two age groups get together there are benefits to both groups — not to mention heart-warming interactions.

“We live in a mobile society, so kids do not have access to their grandparents like they used to,” Sue Davidson, director of the center, told TODAY. “So having those seniors around that they can build those relationships with is not only heartwarming, but beneficial.”

With the hope of allowing the old and young to benefit from one another, Davidson and her staff set out to find similar care facilities, as well as research that supported their goals. They quickly found Dr. Shannon Jarrott’s research, and went to visit her program at the University of Virginia, where she had started a program with similar initiatives.

"We built a hallway that connects the two wings," said Davidson. "The kids call it the pathway because it goes both ways." Courtesy Bethlehem Intergenerational Center

“We know that children benefit from having that consistent, caring adult in their lives,” Jarrott told TODAY. “And when seniors are invited to contribute in an age appropriate and ability appropriate manner it gives a role back to them as well.”

Davidson's group took what they saw and traveled the country in search of other programs as well. They took everything that they learned, and developed a care center they felt would benefit their specific community's needs.

“The caregivers have a safe place where they can enhance their family member’s quality of life,” said Davidson. “It can give the caregivers a break that they desperately need for themselves.”

"The older adults tell us that they love to watch the children," said Jarrott. Courtesy Bethlehem Intergenerational Center

The Bethlehem Center launched this program in June, but the children’s program has been around for 46 years. The center operates as a day center for both age groups, and schedules one intergenerational group activity per day with children ranging in age from infancy to kindergarten. The older kids have plenty of time to interact with the elders as well as before and after school.

“There’s lots of activities for them to do, but they can also choose — one of our little ones taught a senior how to crab walk last week,” said Davidson. “The sweet thing is they now know each other’s names and they ask for each other. That’s the part that melts my heart.”

Jarrott confirmed that her research has consistently shown that elders are still “interested in being active and contributing members of society.” These programs fulfill that sense of purpose.

Jarrott emphasized that elders and children aren’t the only groups that can benefit from intergenerational relationships — they're great for all ages.

“There’s just something that you can achieve by bringing generations together,” said Jarrott. “I encourage people to take an intergenerational lens to everything that they do.”

As for the Bethlehem Center, the Grand Rapids community seems to agree. The program has been growing and Davidson is hopeful that it can provide a constant light for the community.

“The interactions are so real,” said Davidson. “It is so beautiful.”

Output: The center in Grand Rapids, Michigan, is home to day care and senior care facilities, and when these two age groups get together there are benefits to both groups — not to mention heart-warming interactions.


Instruction: create a high quality summary of the given input

Input:
'Ahead of the game': Florida seniors, nursing homes prep for Hurricane Irma
 Story highlights NEW: At least 24 nursing homes and 108 assisted-living facilities across South Florida are evacuating "They keep very close tabs on us, because this is our life," one senior says

CNN —

Cypress Village, a senior living facility in Jacksonville, Florida, is Herbert Dreisbach’s home – and when Hurricane Irma hits, he doesn’t plan to leave his home.

This will be the first hurricane that he and his wife, Joanne, will experience while living on the third floor at Cypress Village, with a view of a lake and surrounding pine and cypress trees, Dreisbach said.

Joanne and Herbert Dreisbach plan to stay at their senior living community in Jacksonville, Florida, when Hurricane Irma hits. Lisa Brown

“We are perfectly safe here. This is a very nice, sturdy concrete building, and we feel very secure here, and they are taking very good care of us, so we’re satisfied to stay here,” the 94-year-old said.

The power might go out, “and I know some of these things might happen to us, but it’s still better than being at a facility that would not be properly prepared to take care of us,” he said just a few hours before a 3 p.m. meeting to inform residents of how to prepare for the hurricane.

“We’re all meeting downstairs for another series of instructions if need be,” he said. “They keep very close tabs on us, because this is our life.”

Lisa Brown says her father's facility is the safest place for him. Lisa Brown

As Hurricane Irma barrels toward South Florida, Dreisbach’s daughter Lisa Brown knows that staying in his assisted-living community is the safest option for her father, she said.

Yet all the way across the country in Palo Alto, California, she still worries.

“Florida is, in my opinion, a gold standard state in that the Florida Health Care Association, state disaster planners and nursing home staff have been extremely proactive in making sure that facilities are ready for a hurricane,” said Brown, a professor of psychology and director of the Trauma Program at Palo Alto University.

One benefit is that the association has been “reaching out prior to a hurricane to emergency operation center leadership so they’re aware of … the needs that residents have and there’s no surprises that are taking place when the threat is imminent,” she said.

Brown, who is not involved with the health care association, has conducted research on how hurricane threats and evacuations affect nursing home residents.

“Not all residents, our research clearly showed, should be evacuated. Those who can safely shelter in place may fare much better than those who are physically evacuated,” she said. “There’s not a one-size-fits-all, is the main point.”

‘We are right now sheltering in place’

Nursing homes and assisted-living facilities across South Florida are preparing for Hurricane Irma to strike, and they have emergency and evacuation plans in place to help keep seniors safe.

The Florida Health Care Association, a federation representing 81% of the state’s nursing centers, has been hosting daily disaster calls with nursing homes and assisted-living facilities to help them prepare for the storm, association spokeswoman Kristen Knapp said.

As of Friday morning, at least 24 nursing homes and 108 assisted-living facilities have been evacuated, Knapp said. The association has been monitoring bed availabilities for evacuees across the state, she said, as well as availabilities in Alabama, Mississippi, Louisiana and Georgia.

The Florida Department of Health has coordinated the evacuation of 17 hospitals and 196 non-hospital health care facilities, according to the Florida Division of Emergency Management website.

On Friday, the Division of Emergency Management issued an executive order giving districts and out-of-state licensed nurses 30-day permission to provide health care services and treatment to Florida nursing home residents who are evacuating, Knapp said.

Additionally, “if, post-impact, we need more nurses to come in and assist, then out-of-state nurses can come and provide care,” Knapp said of the executive order.

In Florida, mandatory evacuations orders included parts of Miami-Dade County, Broward County east of US 1, Palm Beach County, low-lying parts of Brevard County and Monroe County, home to the Keys.

In the case of mandatory evacuations, many facilities are prepared with residents’ medications and other needs.

“Each facility has been instructed to prepare in advance seven to 10 days of medication, oxygen and other medical necessities for each resident. The facility packages the medications, along with the current orders, and sends (them) with the resident in the case of an evacuation,” Knapp wrote in an email.

“Pharmacies are refilling medications to ensure that facilities can send an ample supply with the residents,” she said. In other words, “if evacuation is instructed by local or state authorities, residents needing medication will be authorized for refills on any and all medications, regardless of last refill date.”

Holiday Retirement, which owns 30 assisted- and senior living communities across Florida, housing 3,900 seniors, has been working closely with the Florida Health Care Association in preparation, said Lori Colwell, the company’s district vice president of operations for Florida.

As of Friday afternoon, the only Holiday retirement community under mandatory evacuation orders wasn’t in Florida but rather in Savannah, Georgia, spokeswoman Hannah Rimar said.

The Hilton Head, South Carolina, facility may be evacuating shortly as well, she said.

Holiday Retirement communities in Florida have buses on standby in case of evacuation, more than 400 cots and linens, three days’ worth of nonperishable foods in addition to twice their normal supply of food, 300 gallons of spring water and generator backups in case the communities lose power, Colwell said.

As for residents’ medications, the communities have been supplied with a one-week emergency medication supply on top of the 30-day supply they have for residents, Colwell said.

“If we indeed need to evacuate, we do ask the residents to pack three to five days of clothing,” she said. “We are right now sheltering in place until we get the evacuation order.”

Shell Point Retirement Community, which houses 2,400 senior residents in the heart of Southwest Florida’s Gulf Coast, has two on-site hurricane shelters, spokeswoman Lynn Schneider said.

On Friday, Schneider said, the community started to move residents into those shelters, and evacuations into the shelters will continue Saturday morning.

Both shelters are above anticipated storm-surge levels and have emergency generators and emergency food and water supplies, she said.

“Shell Point has a detailed, organized hurricane plan that serves as a guideline in the event of a weather-related emergency. Active tracking begins the moment any tropical storm is named,” Schneider said.

Shell Point residents also are advised to pack personal evacuation kits that include a two-week supply of medications, a three-day supply of special dietary items and ample portable oxygen supplies, among other necessities, she said.

How the past helps prepare for the future

“While Hurricane Charley directly hit Southwest Florida in 2004, Shell Point evacuated 1,750 residents into its hurricane shelter. Medical supplies, food supplies, water and equipment were set up and a special room was dedicated to keeping residents and employee’s pets safe,” Schneider said.

Often, emergencies of the past help to inform preparation for the future, Knapp said.

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“Hurricane Andrew in 1992 brought much attention to how we prepare for these massive storms, both as individuals and as communities. And then, in 2004 and 2005, eight named storms were the catalyst for new preparedness tools and resources for long term care centers,” she wrote. “In 2016, Hurricanes Hermine in late September and Matthew in early October caused major power disruptions, evacuations and $1.59 billion in damages between the two storms, and lessons from these storms have been learned and applied.”

For extreme weather events, Brown said, “I think that everybody benefits – staff, administration, residents, and family members – by having a discussion before this type of weather threat occurs, because once it starts to unfold, it’s difficult to have that discussion then. … Even if you just kind of step through what you would do and how things would unfold, I think you’re ahead of the game.”

Output: Cypress Village, a senior living facility in Jacksonville, Florida, is Herbert Dreisbach's home -- and when Hurricane Irma hits, he doesn't plan to leave his home.


Instruction: create a high quality summary of the given input

Input:
Largest Assisted Living Chain In U.S. Sued For Poor Care Of Elderly
 About Capitol Desk Capitol Desk delivers the latest in health care policy and politics from Sacramento and around the state. Have an idea? Let us know.

Twenty residents of an assisted living complex in Palm Springs, Calif., missed their medications in a single day because no medical technician was on duty. A woman in a Paso Robles home for seniors pushed her emergency call button after falling in her room and waited 22 hours on the floor with broken bones until staff members responded.

A class-action lawsuit filed last month in a federal district court in Northern California details those incidents and other similar ones, which allegedly occurred in facilities owned by Brookdale Senior Living, the nation’s largest assisted living provider.

The complaint alleges that inadequate staffing, poor worker training and rising fees are part of a “callous and profit-driven approach” that has had “devastating” consequences for Californians living in Brookdale assisted living homes. Residents, it claims, “are left without assistance for hours after falling, they are given the wrong medications, they are denied clean clothing, showers, and nutritious food, and they are left in their own waste for long periods of time.”

Use Our Content This story can be republished for free ( details ).

Relatives of the seniors involved in the lawsuit declined to comment. The California Assisted Living Association, an industry group, also declined to comment.

Brookdale spokeswoman Heather Hunter said in an email that the lawsuit is “without merit” and the company will defend itself “vigorously.”

Tennessee-based Brookdale, which operates 1,121 facilities serving about 100,000 patients in 47 states, has encountered similar complaints elsewhere in the country. A class-action lawsuit filed earlier this year in federal court in Fort Lauderdale, Fla., alleges that the company does not adequately staff its assisted living facilities and is not providing the care it promises residents.

The plaintiff in that lawsuit, Gloria Runton, claimed the Brookdale home where she lives had assured her she would get personal care services based on an assessment of her individual needs, but that as those needs grew over time, the level of her care did not increase. At the same time, Brookdale nearly tripled her fees, she alleges.

The California lawsuit, believed to be the first class-action claim against an assisted living company under the Americans with Disabilities Act (ADA), was filed on behalf of four people currently residing in assisted living homes that Brookdale operates in the state. If the judge certifies the case as a class-action suit, the outcome could affect all residents of Brookdale assisted living facilities in California.

The lawsuit cites not only the federal disabilities law but also several California statutes, including ones that protect against unfair business practices and financial abuse of elders.

Because the goal is to win the case, good lawyers often file a number of claims, said Stephen Rosenbaum, a lecturer at the University of California-Berkeley’s law school and a directing attorney for California Rural Legal Assistance, which is not involved in the lawsuit. “Whether the ADA is the strongest claim is unclear from a strategic standpoint,” he said.

Rosenbaum said case law has not established exactly how the federal disability law applies to assisted living facilities. It is “ironic” that the attorneys in this case are using the disability law to sue Brookdale, given that the company by definition serves people with some kind of disability, he said.

The California lawsuit alleges that some of Brookdale’s facilities don’t meet federal and state accessibility standards. Some of their bathrooms can’t accommodate wheelchairs, and the company doesn’t have an evacuation or emergency plan for disabled residents, the suit claims. Of the four plaintiffs named in the complaint, three require wheelchairs.

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If the case is certified as a class-action lawsuit under the ADA, that would be “big news,” said William Goren, a Decatur, Ga.-based attorney and consultant who helps clients comply with the law. That’s because of the nature of the law itself, he said.

The ADA is designed to address the disabled as individuals whose disabilities can be accommodated in different ways, Goren said. But a class-action lawsuit requires the “class” of plaintiffs to show that they’ve been injured in the same way.

“It’s very, very unusual that you could go in and get a class-action certified under the ADA,” Goren said. “It can happen, but not often.”

In California, Brookdale Senior Living runs 89 homes and serves up to 5,000 patients, offering various combinations of independent living, assisted living and skilled nursing.

In 2014, the company acquired another large assisted living provider, Emeritus, which expanded its presence in California. But the $2.8 billion deal left publicly traded Brookdale with significant staff turnover, declining occupancy and a shaky stock price. A Chinese real estate conglomerate’s recent bid to buy the company reportedly has stalled, creating more uncertainty for Brookdale and the people living in its senior homes.

Residents of Brookdale’s assisted living facilities don’t require the kind of specialized medical care provided in skilled nursing facilities, but they may need help bathing, using the toilet, taking medications, eating or walking. Some residents need walkers or wheelchairs, while others have mild cognitive impairments or dementia. Seniors who require less care and can cook their own meals often choose independent living homes, which Brookdale also operates.

Like many assisted living companies, Brookdale typically charges monthly room and board fees, plus separate charges for additional care, such as help with medications. Its average monthly rate for assisted living, including rent, food and some personal care services, is about $4,000, according to the company’s website.

Both the California and Florida lawsuits claim that to keep its occupancy levels up, Brookdale accepted assisted living residents who might have required higher levels of care, then failed to provide enough staff to meet their needs.

The consequences of leaving residents unsupervised can be severe. In one case, a wheelchair-bound resident of the Brookdale assisted living facility in Elk Grove, Calif., rolled herself out an open door and fell off a curb, breaking her neck, according to an investigation by the California Department of Social Services, which regulates assisted living facilities. The April 2 incident merited a civil penalty, still to be determined, according to the agency’s investigator. That episode was not mentioned in the lawsuit.

Tony Chicotel, a staff attorney at California Advocates for Nursing Home Reform, which is not involved in the suit, said inadequate staffing is a problem at many assisted living facilities.

Assisted living salespeople tell seniors they can meet all their current and future needs, Chicotel said. “But … the facility will only staff based on revenue they’re getting … at least at the big facilities.” The bottom line, he said, is that residents “don’t get the care they need.”

Output: Twenty residents of an assisted living complex in Palm Springs, Calif., missed their medications in a single day because no medical technician was on duty. A woman in a Paso Robles home for seniors pushed her emergency call button after falling in her room and waited 22 hours on the floor with broken bones until staff members responded.


Instruction: create a high quality summary of the given input

Input:
UK MPs to quiz FCA over listing proposal amid Aramco suspicion

The Financial Conduct Authority is facing questions from MPs about whether political influence was behind proposed City rule changes that could lure the $2tn (£1.5tn) float of Saudi Aramco to London.

Andrew Bailey, the chief executive of the FCA, is being asked by the chairs of two powerful Commons committees whether there were any discussions between the City watchdog and ministers ahead of the consultation on the planned changes.

The FCA did not mention Aramco when it began consulting on its proposal to create a new category for firms controlled by a shareholder that is a sovereign country. But the plan was immediately seen as an attempt to lower any barriers to the $2tn Saudi oil company picking London for its stock market listing, which could boost the UK in the wake of Brexit.

Major City investors warned the plans could damage London’s reputation and the matter is now being raised by Nicky Morgan, the Conservative MP who chairs the Treasury select committee, and Rachel Reeves, the Labour MP who chairs the business, energy and industry committee.

In a joint letter, the two chairs tell Bailey: “We are interested to explore the rationale for this consultation, particularly given the concerns expressed by shareholders that these proposals would weaken protection for private investors against interference from foreign sovereign company owners.”

They pose seven questions for Bailey, including “to what extent was the FCA aware of any interest shown by Saudi Aramco in obtaining a UK listing, and if known, how far that interest influenced the consultation?”

They also ask: “What discussions did the FCA (whether at board or working level) have with ministers or officials from government departments in advance of and during the consultation, and in particular on the balance between attracting foreign investment and maintaining the integrity of the UK markets?”

The committees are being reformed after the July general election and are likely to be formally constituted next week. Both Morgan and Reeves said they would discuss Bailey’s response with their members, signalling further scrutiny from the MPs.

Saudi Arabia is planning to sell off a wide range of assets in the face of a weak oil price. The sale of a 5% stake in Aramco - probably next year – is key to the plan and could value the entire company at $2tn. The Financial Times reported on Thursday that some changes were made to parts of the economic transformation plan but that these would not affect Aramco’s sell-off.

London and New Year are regarded as vying for the listing and in April Theresa May and Xavier Rolet, chief executive of the London Stock Exchange, visited Riyadh to meet Aramco’s chief executive, Khalid al-Falih, who is also the kingdom’s energy minister.

The FCA proposals would enable state-owned companies to qualify for a premium listing – which has more onerous corporate governance rules and is valued by investors – but escape two key hurdles. One relates to how the company and the controlling shareholder conduct deals with each other; the second allows investors a vote on independent directors.

Morgan said: “The UK has a world-class reputation for upholding strong corporate governance. The FCA must protect this reputation, especially as the City looks to remain competitive and thrive post-Brexit. Any changes mustn’t dilute the protection afforded by the ‘premium listing’ brand.”

She said the FCA’s consultation would be examined by the Treasury select committee, which she was elected to chair after the general election in July.

Reeves said that while it is important for the UK to thrive after Brexit it should not be at the expense of a weaker corporate governance regime. “Getting this balance right will be vital to the UK’s long-term future as a key financial centre and an attractive market-place place for investors. The FCA’s consultation relating to its premium listing regime raises questions about the UK’s reputation for sound corporate governance.”

The FCA confirmed it had received the letter and that it would reply in due course. At the time of the consultation, Bailey said sovereign owners had different motivations from private sector individuals or companies. The consultation ends on 13 October.

Output: MPs on two powerful committees will probe the UK's financial regulator on whether political influence was brought to bear on a proposal to loosen listing rules that could have attracted the $2tn flotation of Saudi Arabian oil corporation Aramco. The head of the Financial Conduct Authority, Andrew Bailey, will face the Treasury select committee and the business, energy and industry committee on whether the watchdog met ministers before considering the proposal. The FCA didn't mention the company, Aramco, when announcing its intention to explore the plan.


Instruction: create a high quality summary of the given input

Input:
NFL launches subscription streaming service to conquer Europe
 The NFL is betting on a new subscription streaming service as it tries to push further into Europe.

American football has gone from hosting one live game in London to four over the last decade. But now, the NFL is trying to grow its streaming service that charges people £139.99 ($183) a year for access to more than 300 games on demand a season.

The Netflix-style Game Pass service has been overhauled for the 61 European markets the NFL operates in ahead of the new season, which started Sept. 7. Subscribers get access to award-winning shows and behind-the-scenes content as well as the option to watch every game. The NFL owns Game Pass, but a joint venture of Bruin Sports Capital, its sports media entity Deltatre and WPP runs the service.

To survive, sports organizations must own the relationship with their fans, said Alistair Kirkwood, the managing director of NFL UK. “Streaming hasn’t been at the forefront of our business, but increasingly over the next five years, Game Pass will be seen as a major part of our business strategy,” he said.

It’s a lofty goal for a sport that’s competing outside of its home base and at a time when illegal streaming is rife. Kirkwood believes there’s big value in having a fan database, though. Early results from the content tested on the service during the preseason have been encouraging; the NFL doesn’t disclose numbers but said Game Pass has posted record numbers of people signing up for free seven-day trials and then later purchasing the product, and people have streamed up to 12 live preseason games on some days, said Sam Jones, CEO of the joint venture for Game Pass. Kirkwood is also encouraged by meetings he’s had with Amazon Prime after the two organizations struck a deal earlier this year to stream 11 games to Prime subscribers.

But James Kirkham, head of sports publisher Copa90, said that to really scale, the NFL will have to create exclusive content that’s tied to the games: “stunning, iconic [film] content, which people will queue up to watch.”

The NFL has limited popularity beyond the U.S. But Game Pass and Amazon are also exercises in how data has quickly become a currency in sport. Amazon gets data on NFL fans to whom it could potentially sell products and attract sponsors, while the NFL gets the reach of a platform that has at least 66 million subscribers and potential interest from advertisers who want to target sports fans.

Yet for all of Amazon’s potential, Kirkwood stressed that the streaming partnership is still just an experiment and downplayed concerns that Amazon’s or Facebook’s moves into sports broadcasting are a threat to the NFL’s own efforts to own a larger slice of the league’s viewership. He believes the NFL will be able to deliver tailored content, targeted to those who want it most, when and how they want it.

“Maybe I’m naive, but I don’t think about what I’m not getting [from deals with the technology players],” he said. “I focus on what I will get, which will be complementary to other platforms we’re on. Facebook Live, for example, will give me something else that maybe our own channels like Game Pass or the BBC won’t get or vice versa.”

In 2022, the NFL will be at the end of its five-year game plan for streaming in Europe, the same year its lucrative TV rights are up for grabs in the U.S. By then, the league’s executives in each of those 61 markets will have shared so much information with the NFL’s main team in New York that it could be set to capitalize on any interest from the likes of Amazon or Facebook, should it manifest.

Photo courtesy of NFL UK

Output: The NFL has launched its subscription-based streaming service Game Pass in Europe as it seeks to expand its footprint beyond the US. For £139.99 ($183) per year, users have access to over 300 games of american football per season, as well as exclusive content. Record numbers of people had taken up the free trial and subscribed, said Sam Jones, CEO of the joint venture for Game Pass. NFL UK has also signed a deal with Amazon Prime to stream 11 games, which could be critical in 2022, when the NFL's five-year plan for streaming in Europe is slated to end.


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Chinese solar firms excluded from EU's minimum price undertaking

 The European Commission (EC) has decided to exclude Chinese PV manufacturers AE Solar and Wuxi Saijing from the minimum price undertaking for the import of solar modules from China, according to a document published in the EU Official Gazette on Wednesday.

The EC said that AE Solar has provided incomplete quarterly reports on its sales, while Wuxi Saijing has set up a trading system with an independent importer, which has allowed the company to sell the solar modules under minimum import prices in Europe after the entry into force of the undertaking. Furthermore, Wuxi Saijing has conducted compensation transactions with the customer, thus circumventing the rules. This would have been confirmed by customs investigations.

The two Chinese solar manufacturers were not able to provide evidence against the allegations, the EC said. Some invoices of AE Solar and even more of Wuxi Saijing were declared invalid by Brussels authorities. The custom authorities were instructed to impose antidumping and anti-subsidy duties on the companies.

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Currently, the EC is conducting a mid-term review of the undertaking, which is expected to investigate the gradual mitigation of the antidumping and anti-subsidy measures over the next 18 months. In July, the Commission had proposed a new mechanism for establishing the minimum import price for solar cells and solar modules manufactured in China. It proposed a timetable on how prices should fall by September 2018. A final settlement is currently being discussed. This should be announced in the autumn.

Output: Chinese photovoltaic manufacturers AE Solar and Wuxi Saijing have been excluded from the European Commission's minimum price undertaking and have been slapped with anti-dumping and anti-subsidy duties, according to the European Union Official Gazette. Both firms had invoices that were declared invalid, while AE Solar had provided incomplete quarterly sales reports. In addition, Wuxi Saijing had entered into an agreement with an independent importer before the minimum price undertaking came into effect, allowing it to sell solar modules under minimum import prices in Europe. It also broke the rules by conducting compensation transactions.


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Large firms say they're still unprepared for MiFID II
 With less than four months until MiFID II is implemented in Europe, more than a third of large businesses remain unsure if they will meet the deadline.

A survey carried out by communications technology firm TeleWare suggests smaller firms are more likely to be fully compliant with MiFID II come January 2018 than larger firms.

The poll of 100 senior decision makers across financial services found 28% of firms overall are unsure if they’ll be ready in time, but 38% of firms considered large stated they may not meet the deadline.

On the other hand, all firms considered small - with less than 10 employees overall - said they are fully confident about being MiFID II compliant by January next year.

Steve Haworth, CEO of TeleWare, explained MiFID II is a complex directive which affects a variety of functions within each business.

“Firms need to look outside of their immediate business to find the compliance answer… With technology underpinning operations, it’s highly encouraging that firms are investing in this area ahead of January 2018,” he added.

The research also found 71% of firms questioned investment in IT systems ahead of January 2018, following the European Commission’s decision to delay the regulation.

A separate survey of asset managers carried out by Liquidnet also suggests a lack of confidence about meeting the deadline, particularly around best execution requirements.

Just 6% of buy-side firms surveyed by Liquidnet said they are currently ready to meet MiFID II’s best execution rules.

Output: More than a third of large companies are unsure if they'll meet the deadline for MiFID II's wide-ranging regulatory reforms in January, according to a survey by communications technology firm TeleWare. Findings of the poll of 100 senior decision makers suggests smaller firms are more likely to be fully compliant with the European directive. A separate survey of asset managers by Liquidnet found just 6% of buy-side firms said they were ready to meet MiFID II’s best execution rules.


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Deutsche Börse, Illuminate lead $5m funding for RegTek.Solutions
 Deutsche Boerse and venture capital firm Illuminate Financial Management have co-led a $5 million funding round for RegTek.Solutions.

Launched earlier this year and based in New York, RegTek.Solutions is a specialist provider of regulatory compliance software.

It provides trade reporting tools and software in a bid to improve the quality, transparency and control of regulatory reporting obligations across various jurisdictions.

Deutsche Boerse’s head of market data and services, Holger Wohlenberg, and managing partner at Illuminate Financial Management, Mark Beeston, will become non-executive board members at RegTek.Solutions.

Brian Lynch, CEO at RegTek.Solutions, explained the investment from both parties is “real validation of our offering and prospects of growth”.

He added: “As the next bottleneck of regulatory deadlines nears and both sell-side and buy-side firms grapple with adhering to the new rules, we are seeing strong demand across the market for outsourced trade reporting tools.”

Ankur Kamalia, head of venture portfolio management at DB1 Ventures - Deutsche Boerse’s corporate venture capital arm - explained RegTek.Solutions established itself as a reliable service provider with knowledge within the post-trade space.

The investment made in exchange for a minority stake will be used to scale RegTek.Solutions’ operations ahead of MiFID II.

Output: German shares and securities marketplace operator Deutsche Börse has joined with venture capital firm Illuminate Financial Management in a $5m funding round for RegTek.Solutions, which provides regulator compliance software designed to improve the quality, transparency and control of regulatory reporting obligations in a number of jurisdictions. RegTek.Solutions anticipates a growing need for its services in light of new Mifid II regulations that are due to come into force next year.


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143 million Americans' private records stolen from Equifax
 Credit reporting agency Equifax announced today (Sept. 7) that hackers stole records containing personal information on 143 million of its customers in the United States.

“On July 29, 2017, Equifax discovered that criminals exploited a U.S. website application vulnerability to gain access to certain files,” the company said in a statement. “Most of the consumer information accessed includes names, Social Security numbers, birth dates, addresses, and in some instances, driver’s license numbers. In addition, credit card numbers for approximately 209,000 consumers.”

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The company added that 182,000 credit-dispute documents, which contain personal information, were also stolen.

Shortly after the announcement, Bloomberg News reported that three executives at Equifax sold nearly $1.8 million worth of company shares after the data breach had been discovered in late July. The company’s stock dropped more than 12% in after-hours trading following the announcement at about 4:30pm ET.

Equifax has created a website to help its customers find out whether their data has been stolen.

Output: Hackers have stolen masses of sensitive data from Credit reporting agency Equifax. The company revealed that data on 143 million US citizens - nearly half of the country's population - was illicitly accessed; the firm's stock plummeted following the news. The data included social security numbers, birthdays, addresses and credit card numbers. UK and Canadian citizens have also been affected by the breach.