The noise cost of reservoir locality in broadband quantum amplifier chains
Abstract
Directional quantum amplifiers enable weak-signal readout while protecting the source, but reservoir noise limits sensitivity. Finite-band suppression must reconcile frequency-dependent responses with fixed local couplings and finite rates. We construct adjacent-site loss channels attaining the known single-frequency minimum under local compatibility conditions, as an uncapped benchmark. For specified uniform and dimerized chains, we compare fixed reservoirs at matched drift, ports, high-gain band and complete gain/loss rate caps. At the representative cap R=8 and halfwidth Ω=0.05, nearest-neighbor arithmetic band average noise exceeds the unrestricted optimum by more than $1.01265$ quanta in the uniform chain for every finite N≥64. Boundary-response bounds give necessary rates and targets requiring range two. At N=64, finite-auxiliary calculations retain a noise advantage under matched total coupling budgets; response bounds quantify noise-resolution tolerances. These theoretical results guide reservoir design and noise calibration for a proposed cryogenic microwave array with a $100$ kHz design band.
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BibTeX
@misc{li2026noise,
title = {{The noise cost of reservoir locality in broadband quantum amplifier chains}},
author = {Chengxi Li and Hao Zhu and Tie-Fu Zhang and Lin Zhuang and Wanzi Sun and Wuming Liu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20654},
eprint = {2610.20654},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20654},
}
RIS
TY - UNPB
TI - The noise cost of reservoir locality in broadband quantum amplifier chains
AU - Chengxi Li
AU - Hao Zhu
AU - Tie-Fu Zhang
AU - Lin Zhuang
AU - Wanzi Sun
AU - Wuming Liu
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.20654
UR - https://arxiv.org/abs/2610.20654
AB - Directional quantum amplifiers enable weak-signal readout while protecting the source, but reservoir noise limits sensitivity. Finite-band suppression must reconcile frequency-dependent responses with fixed local couplings and finite rates. We construct adjacent-site loss channels attaining the known single-frequency minimum under local compatibility conditions, as an uncapped benchmark. For specified uniform and dimerized chains, we compare fixed reservoirs at matched drift, ports, high-gain band and complete gain/loss rate caps. At the representative cap R=8 and halfwidth Ω=0.05, nearest-neighbor arithmetic band average noise exceeds the unrestricted optimum by more than $1.01265$ quanta in the uniform chain for every finite N≥64. Boundary-response bounds give necessary rates and targets requiring range two. At N=64, finite-auxiliary calculations retain a noise advantage under matched total coupling budgets; response bounds quantify noise-resolution tolerances. These theoretical results guide reservoir design and noise calibration for a proposed cryogenic microwave array with a $100$ kHz design band.
ER -