Observation of feedback-directed quantum dynamics in large-scale quantum processors

TL;DR

This paper demonstrates feedback-controlled quantum circuits on large-scale quantum processors, enabling non-unitary dynamics and asymmetry in quantum simulations through real-time measurements and adaptive operations.

Contribution

It introduces a novel feedback-directed circuit architecture that actively controls quantum dynamics, expanding the capabilities of programmable quantum hardware.

Findings

Successfully simulated feedback-induced asymmetry on 100-qubit processors.

Observed noise-resilient signatures of feedback-driven non-Hermitian effects.

Demonstrated directional information flow in large-scale quantum circuits.

Abstract

Programmable quantum hardware provides an emerging platform for exploring and controlling non-unitary quantum dynamics through measurement-based operations. In this work, we introduce feedback-directed circuit architectures that integrate spatially structured mid-circuit measurements with real-time conditional operations to steer the evolution of random dynamics, and perform their large-scale simulations (up to 100 qubits) on programmable digital quantum processors. By promoting measurement from a passive readout to an active control signal, these adaptive monitored circuits enable directional information flow and generate intrinsic asymmetry in random circuit simulations. We implement this framework on IBM superconducting quantum processors and observe robust, noise-resilient signatures of feedback-induced asymmetry distinct from the more well-known non-Hermitian skin effect. Our results establish feedback as a programmable resource for non-unitary control, opening new avenues for engineering measurement-based dynamics, non-equilibrium phenomena, and tunable open-system behavior on large-scale quantum hardware.