Or and Aharonov.
Scaling up the number of these things allows the controlling of noise-based error below a certain threshold according to a theorem proved by Or and Aharonov. Rapid phase shifts of these things can prevent their amplitude evolution in a procedure called "bang-bang control." Two paths through a Mach-Zender interferometer are used to distinguish states of these things in time-bin encoding. Superdense coding is a procedure for sending one of these things after forming a (*) Bell pair. These things are a superposition of the ket of zero and the ket of one, which allows unitary transformations of these things to be represented as rotations on a Bloch (block) sphere; those unitary transformations of them include the Hadamard and C-NOT gates. The fact that these things can be entangled allows them to perform several calculations simultaneously. For 10 points, name these simplest units of information in a quantum computer.
Scaling up the number of these things allows the controlling of noise-based error below a certain threshold according to a theorem proved by
qubit [or quantum bit; prompt on "quantum computer" until mention; prompt on "quantum states"]