What question did this study set out to answer?

To develop a feedforward protocol that utilizes decoherence for better quantum control and measurement accuracy.

April 3, 2026Open Access

Bell Decay Clock: Extracting Useful Information from Decoherence via Mid-Circuit Measurement Feedforward

Key Points

To develop a feedforward protocol that utilizes decoherence for better quantum control and measurement accuracy.
Implemented a feedforward protocol to manage decoherence.
Conducted mid-circuit measurement on entangled states to extract classical information.
Compared the Bell Decay Clock with conventional ZZ clock over multiple qubit pairs.
Bell clock maintains GPS > 0 over a wider window compared to ZZ clock.
ZZ clock fails entirely while Bell clock performs successfully with positive GPS.
MCM feedback was identified as an active mechanism for enhancing performance.

Abstract

A feedforward protocol that converts decoherence into an information resource for quantum control. The Bell Decay Clock encodes timing information in measurement-resolved decay pathways of entangled states, enabling mid-circuit measurement (MCM) to extract useful classical information even after phase coherence is lost. Key results:- IBM Heron: Bell clock maintains GPS > 0 over 3-4x wider window than ZZ clock (18/18 points, z > 5σ)- IQM Garnet: ZZ clock fails completely (GPS < 0, all points), Bell clock succeeds (GPS = +0.19, 4.4σ)- Static vs Dynamic control: ΔGPS = +0.55 isolates MCM feedback as active mechanism- Universal feedforward phase ϕ* = 0.873 rad verified across 3 independent qubit pairs Related: EEDT protocol (DOI: 10.5281/zenodo.19029431)Code: https://github.com/okudat9/Quantum-6502

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