Journal Article

FZJ-2025-02251

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Stabilizing two-qubit entanglement with dynamically decoupled active feedback

Greenfield, S. ; Martin, L. ; Motzoi, F.FZJ* ; Whaley, K. B. ; Dressel, J. ; Levenson-Falk, E. M.

2024
American Physical Society College Park, Md. [u.a.]

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Please use a persistent id in citations: doi:10.1103/PhysRevApplied.21.024022

Abstract: We propose and analyze a protocol for stabilizing a maximally entangled state of two noninteracting qubits using active state-dependent feedback from a continuous two-qubit half-parity measurement in coordination with a concurrent, noncommuting dynamical decoupling drive. We demonstrate that such a drive can be simultaneous with the measurement and feedback, while also playing a key part in the feedback protocol itself. We show that robust stabilization with near-unit fidelity can be achieved even in the presence of realistic nonidealities, such as time delay in the feedback loop, imperfect state-tracking, inefficient measurements, dephasing from 1/𝑓-distributed qubit-frequency noise, and relaxation. We mitigate feedback-delay error by introducing a forward-state-estimation strategy in the feedback controller that tracks the effects of control signals already in transit. More generally, the steady state is globally attractive without the need for ancillas, regardless of the error state, in contrast to most known feedback and error-correction schemes.

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Contributing Institute(s):

1. Quantum Control (PGI-8)

Research Program(s):

1. 5221 - Advanced Solid-State Qubits and Qubit Systems (POF4-522) (POF4-522)

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Essential Science Indicators ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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