What is a qubit?
The basic unit of a quantum computer: it can be 0, 1, or a blend of both until it is measured.
A qubit holds two numbers, called amplitudes, one for 0 and one for 1. Their sizes set the chance of each result when the qubit is measured, and measuring always returns a plain 0 or 1.
Qubits are built from tiny physical systems that follow quantum rules. Google and IBM use loops of superconducting metal cooled close to absolute zero. Other companies use single charged atoms held in place by electric fields, neutral atoms held by lasers, or particles of light.
In the lessonsSee it in a simulation
Related
- BitThe smallest unit of ordinary information: a 0 or a 1.
- SuperpositionA qubit state that is a blend of 0 and 1, with an amplitude for each.
- AmplitudeThe number a qubit holds for each possible result. Squaring it gives the chance of that result.
- MeasurementReading a qubit. It returns 0 or 1 at random, with chances set by the squared amplitudes, and ends the blend.
- Physical qubitOne actual qubit on a chip or in a trap. Physical qubits make errors, roughly once every few hundred to few thousand operations today.