A qubit—short for "quantum bit"—is probabilistic binary in the world of quantum mechanics.

While a bit in computing is either 0 or 1, a qubit (or quantum bit) is the analog of a bit for quantum computation. Unlike an ordinary bit, which may only assume two possible values (usually called 0 and 1), a qubit takes on a range of values between 0 and 1, each having different probabilities. Complex numbers are typically used to express this continuum of possible values.