hole spin-orbit qubit structure. See also Ancilla bit Bell state, W state and GHZ state Bloch sphere Physical and logical qubits Quantum register Two-state quantum system The elements of the group U(2) are all possible single-qubit quantum gates The circle group U(1) define the phase about the qubits basis states Notes References Further reading A treatment of two-level quantum systems, decades before the term “qubit” was coined, is found in the third volume of The Feynman Lectures on Physics (2013 ebook edition), in chapters 9-11. A non-traditional motivation of the qubit aimed at non-physicists is found in Quantum Computing Since Democritus, by Scott Aaronson, Cambridge University Press (2013). An introduction to qubits for non-specialists, by the person who coined the word, is found in Lecture 21 of The science of information: from language to black holes, by Professor Benjamin Schumacher, The Great Courses, The Teaching Company (4DVDs, 2015). A picture book introduction to entanglement, showcasing a Bell state and the measurement of it, is found in Quantum entanglement for babies, by Chris Ferrie (2017). . Quantum computing Quantum states Teleportation Units of information Australian inventions