Tuesday, March 22, 2005

 

Definition of a Qubit ....

The following is from a paper on Quantum Computers by Bernard Oemer


Definition 1 (Qubit) A qubit or quantum bit is a quantum system whose
state can be fully described by a superposition of two orthonomal eigenstates
labeled 0> and 1>.

The general state psi> in H of a qubit is given by

psi> = a0> + b1> with a**2 + b**2 = 1

The value of a qubit is the observable N with the Hermitian operator

Ni> = i> over the Hibert space H = C*2 .

[0 0]
N = [0 1] .

[0 0] [a]
= = ( a* b*) [0 1] [b] = b**2.


Thus gives the probability to find the system in state 1> if a
measurement is performed on the qubit.

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