What is phase in a qubit?
The part of an amplitude beyond its size. It decides how amplitudes add up or cancel.
In real qubits, amplitudes are complex numbers, so each has a size and a direction, like a clock hand. The direction is the phase. Two amplitudes with opposite phases cancel, and two with the same phase add up.
Positive and negative numbers are the simplest case: two opposite directions. The lessons use only those, and every idea in them works the same way with full phases.
Related
- AmplitudeThe number a qubit holds for each possible result. Squaring it gives the chance of that result.
- InterferenceAmplitudes adding up or cancelling when they combine. Quantum algorithms use it to make wrong answers unlikely.
- QubitThe basic unit of a quantum computer: it can be 0, 1, or a blend of both until it is measured.