Four qubits in the dark, played as a sequencer. Gates put them into superposition and link them together. A measurement collapses each one to 0 or 1, and that result is the note. Linked qubits answer each other instantly, the vacuum hums underneath, and the environment slowly wears every link away.
Saved circuits keep the gates, qubits, decoherence, voice, filter, space and pulse in this browser.
Dephasing breaks interference: a step that should cancel to silence starts to sound at random. Relaxation leaks energy, like spontaneous emission, so 1s fade back to 0 and the qubits go quiet. Sparks on the stage mark each hit from the environment.
When measuring one qubit settles another one's answer, that partner sounds a quiet echo right away, before it is measured itself.
The drone never stops while playing. With one certain result it is a low open fifth; as the state spreads across many results, a minor second and a tritone creep in, following the entropy of the state. The environment gets louder with decoherence: each phase hit crackles, and each decay from 1 to 0 sighs downward. Dread rises into a measurement and cuts off as it lands, louder the less certain the result.
Uncertain results strike harder than certain ones. Between measurements each qubit hums both of its possible notes, weighted by their odds: bright while in clean superposition, darker once entangled or worn down. Its phase is heard as beating, slow and calm for |+⟩, uneasy for |−⟩. Echoes arrive reversed, an octave down.
How many Hadamards, links, measurements and phase moves the circuit holds sets how many hits each lane gets in the bar, one cell per step. Hadamards pound with a low, rumbling kick, links clank like chains at the second qubit's pitch, measurements click like a Geiger counter, phase moves slam sheet metal. Grit drives it all through a broken mixer; past halfway it starts to crush.
Left–right opens the filter, up adds resonance. The coloured lines are each qubit's notes; the shaded band is how far the sweep moves.
Each qubit's notes are scale degrees, so changing the key or scale moves every part together. "Two notes" plays the note two scale steps below for a 0. "Walk" climbs a step for each 1 and drops one for each 0.