Independent density and coherence skin effects in adaptive fermion circuits
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.
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BibTeX
@misc{chahine2026independent,
title = {{Independent density and coherence skin effects in adaptive fermion circuits}},
author = {Karim Chahine and Markus Siegl and Michael Buchhold},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.36017},
eprint = {2609.36017},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36017},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Independent density and coherence skin effects in adaptive fermion circuits
AU - Karim Chahine
AU - Markus Siegl
AU - Michael Buchhold
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.36017
UR - https://arxiv.org/abs/2609.36017
AB - 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.
ER -