Quantum Feedback Delay Networks

Feedback delay networks are signal-processing structures, extensively used in digital audio effects and artificial reverberation, that can be designed around a unitary matrix that multiplies the vector output of a bunch of delay lines. Replacing matrix-vector multiplication with unitary evolution of a quantum state, a new class of signal-processing structures is created, whose behaviour and sonic properties are being explored. The output of 2n delay lines is encoded in an n-qubit quantum state that is made to be evolved and temporarily stored in the feedback loop, being subject to quantum as well as to classical operations.