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This research demonstrates how adaptive fermion circuits can independently tune density and coherence skin effects, enabling distinct localization at opposite edges through topological transitions. By decoupling these phenomena via conditioned feedback loops, the study offers new pathways for engineering nonreciprocal quantum dynamics without relying on postselection. Such control over stationary states and coherence decay is critical for advancing adaptive quantum computing architectures.
Independent density and coherence skin effects in adaptive fermion circuits
arXiv:2609.36017v1 Announce Type: new Abstract: Adaptive circuits use measurements and outcome-conditioned feedback to implement nonreciprocal dynamics without postselection. We show that fermion circuits host independently tunable density and coherence skin effects. The stationary state has an exact density tilt set only by measurement strength and feedback displacement: conditioned-gate details cancel, yielding an exponential one-particle profile and, at any filling, a tilted ensemble of configuration weights. Decaying coherences instead obey, in the bulk, an effective Hatano-Nelson generator controlled by the conditioned gates through a relative occupation phase. Tuning this phase drives a point-gap topological transition and reverses coherence localization at fixed density, allowing density and coherence to localize at opposite edges. We derive both exponents for conditioned $U(2)$ gates and propose a correlator-ratio probe using ensemble-averaged observables.
Abstract:Adaptive circuits use measurements and outcome-conditioned feedback to implement nonreciprocal dynamics without postselection. We show that fermion circuits host independently tunable density and coherence skin effects. The stationary state has an exact density tilt set only by measurement strength and feedback displacement: conditioned-gate details cancel, yielding an exponential one-particle profile and, at any filling, a tilted ensemble of configuration weights. Decaying coherences instead obey, in the bulk, an effective Hatano-Nelson generator controlled by the conditioned gates through a relative occupation phase. Tuning this phase drives a point-gap topological transition and reverses coherence localization at fixed density, allowing density and coherence to localize at opposite edges. We derive both exponents for conditioned $U(2)$ gates and propose a correlator-ratio probe using ensemble-averaged observables.
arXiv:2609.36017 [quant-ph]
(or arXiv:2609.36017v1 [quant-ph] for this version)
https://doi.org/10.48550/arXiv.2609.36017 Focus to learn more arXiv-issued DOI via DataCite
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Full text under the publisher's open licence · 210 words
