Optimal phase control of a measurement-assisted quantum refrigerator
Abstract
A tilted nonselective measurement can close the upper transition of a three-level quantum refrigerator, but it also generates coherence that feeds back on the populations and suppresses the cooling current. We formulate randomized open-loop control of the measurement azimuthal phase α, sampled independently at each event from a probability distribution P(α), while keeping the event rate, polar angle, and single-event population-transfer probability fixed. Direct population transfer is phase independent, whereas the coherence source carries the factor e−iα. Exact elimination of the stationary coherence gives 0≤ keff[P]≤ Am, where keff[P] is the effective population-transfer rate between the upper levels and Am is the bare direct mixing rate. When the fixed measurement couples populations and coherence, the upper bound is attained if and only if ⟨ eiα⟩P=0, where ⟨·⟩P denotes an average over the phase distribution. The minimal realization uses two equally weighted phases separated by π: the population-to-coherence source and its return to the populations then vanish at the generator level, while the full direct mixing remains. Because the cold current increases strictly with keff in the refrigeration window, the same condition maximizes the stationary cooling power over the independent random-phase distributions considered here. For one representative parameter set, phase cycling increases the fixed-gap cooling power by about 32% relative to a fixed-phase measurement, while leaving the ratio of extracted cold heat to supplied measurement energy unchanged.
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BibTeX
@misc{liu2026optimal,
title = {{Optimal phase control of a measurement-assisted quantum refrigerator}},
author = {Jinkai Liu and Xian He and Jizhou He and Jianhui Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.04237},
eprint = {2610.04237},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.04237},
}
RIS
TY - UNPB
TI - Optimal phase control of a measurement-assisted quantum refrigerator
AU - Jinkai Liu
AU - Xian He
AU - Jizhou He
AU - Jianhui Wang
PY - 2026
DA - 2026/10/03
PB - arXiv
DO - 10.48550/arxiv.2610.04237
UR - https://arxiv.org/abs/2610.04237
AB - A tilted nonselective measurement can close the upper transition of a three-level quantum refrigerator, but it also generates coherence that feeds back on the populations and suppresses the cooling current. We formulate randomized open-loop control of the measurement azimuthal phase α, sampled independently at each event from a probability distribution P(α), while keeping the event rate, polar angle, and single-event population-transfer probability fixed. Direct population transfer is phase independent, whereas the coherence source carries the factor e^−iα. Exact elimination of the stationary coherence gives 0≤ k_eff[P]≤ A_m, where k_eff[P] is the effective population-transfer rate between the upper levels and A_m is the bare direct mixing rate. When the fixed measurement couples populations and coherence, the upper bound is attained if and only if ⟨ e^iα⟩_P=0, where ⟨·⟩_P denotes an average over the phase distribution. The minimal realization uses two equally weighted phases separated by π: the population-to-coherence source and its return to the populations then vanish at the generator level, while the full direct mixing remains. Because the cold current increases strictly with k_eff in the refrigeration window, the same condition maximizes the stationary cooling power over the independent random-phase distributions considered here. For one representative parameter set, phase cycling increases the fixed-gap cooling power by about 32% relative to a fixed-phase measurement, while leaving the ratio of extracted cold heat to supplied measurement energy unchanged.
ER -