047
Bloch sphere
A qubit driven from pole to pole until its answer flips.
Field
Detail
Study
047
Chapter
Quantum mechanics
Equation
|ψ⟩ = cos(θ/2)|↑⟩ + e^(iφ) sin(θ/2)|↓⟩, Ωt = π
What moves
Ωt, the drive angle; ω, the drive frequency
Structure
Film
Colour means
time
Posted

A single point on a sphere stands for the whole state of a qubit. A drive sets it turning, and it spirals from the north pole to the south, back up, and down again. Measured before the drive, the answer is always up; measured after, always down. The trajectory keeps the colour of the moment it was drawn. Each half-turn of the drive, Ωt = π, flips the state.