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

A qubit driven from pole to pole until its answer flips.

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.

Each study takes one equation and lets the computed result move.