Directional pumping of a two-level system by a fluctuation-regulated quantum source
Abstract
A resonant classical field drives a two-level system coherently and, with ordinary relaxation, produces saturation rather than directional population transfer. Here we show that directionality emerges when the excitation source is retained as a quantum subsystem and subsequently traced out. We model the source as a single-excitation degree of freedom, or equivalently a stream of two-level ancillas, exchange-coupled to a target two-level system. The source first moment generates the usual coherent drive, while its second moments produce upward and downward dissipative channels. For a number-diagonal, fully excited source, the first moment vanishes and only the upward channel remains, yielding monotonic pumping of the target. The same structure follows from both an exact collision map and a fluctuation-regulated second-order quantum master equation. For exponentially decaying source correlations, the pumping rate shows a Lorentzian detuning dependence governed by the correlation time τc, accompanied by a dispersive frequency shift. In the presence of thermal relaxation, the steady-state excited-state population can exceed the resonantly driven optical-Bloch limit of one half. Within the fluctuation-regulated master equation, this directional pumping arises as a drive-induced dissipative contribution whose strength and spectral response are controlled by τc.
Related
- Geometric heat pumping on a quantum processor
- Quantized valley source in bilayer graphene via adiabatic quantum pumping
- Adiabatic preparation of a fractional quantum Hall fluid by coherently pumping atoms from a Bose-Einstein condensate
- Physical-Work Fluctuation Relations from Accessible Quantum Macrostates
- Finite-frequency fluctuation-response bounds for open quantum systems
BibTeX
@misc{fency2026directional,
title = {{Directional pumping of a two-level system by a fluctuation-regulated quantum source}},
author = {Sarfraj Fency and Rangeet Bhattacharyya},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34885},
eprint = {2609.34885},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34885},
}
RIS
TY - UNPB
TI - Directional pumping of a two-level system by a fluctuation-regulated quantum source
AU - Sarfraj Fency
AU - Rangeet Bhattacharyya
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34885
UR - https://arxiv.org/abs/2609.34885
AB - A resonant classical field drives a two-level system coherently and, with ordinary relaxation, produces saturation rather than directional population transfer. Here we show that directionality emerges when the excitation source is retained as a quantum subsystem and subsequently traced out. We model the source as a single-excitation degree of freedom, or equivalently a stream of two-level ancillas, exchange-coupled to a target two-level system. The source first moment generates the usual coherent drive, while its second moments produce upward and downward dissipative channels. For a number-diagonal, fully excited source, the first moment vanishes and only the upward channel remains, yielding monotonic pumping of the target. The same structure follows from both an exact collision map and a fluctuation-regulated second-order quantum master equation. For exponentially decaying source correlations, the pumping rate shows a Lorentzian detuning dependence governed by the correlation time τ_c, accompanied by a dispersive frequency shift. In the presence of thermal relaxation, the steady-state excited-state population can exceed the resonantly driven optical-Bloch limit of one half. Within the fluctuation-regulated master equation, this directional pumping arises as a drive-induced dissipative contribution whose strength and spectral response are controlled by τ_c.
ER -