Natalie Hawkins (return to Home)


Quantum Bits


Definition:

The qubit is a unit of quantum information and represents the state of entanglement in a system.

Two States Possible, Simultaneously

Qubits can be in a superposition of two states at the same time.
The two computational basis states are: |0> and |1>, known as ket0 and ket1.

A pure quantum state can be written as a linear combination of the 2 basis states: |w> = a |0> + b |1>

Probability of Measuring Each State

The probability of outcome |0> is |a|^2, and the probability of outcome |1> is |b|^2.
Since we must measure one state or the other, a and b must be constrained by the equation: |a|^2 + |b|^2 = 1.