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Physical Review Research

Entangled two-photon quantum heat engine: Dissipative nonequilibrium dynamics and correlated statistics

JunJie Chen, Konstantin E. Dorfman

Published Jun 3, 2024• 1 citation
Publisher

Abstract

Recently, the thermodynamics of open quantum systems driven by light fields has been investigated in the framework of quantum heat engines, whose output work can be measured as a spectroscopic signal. In this work, we investigate a four-level quantum heat engine that generates cascaded entangled photon pairs, treating the hot bath as an incoherent thermal pump and focusing on the correlation statistics of the output work and photon indistinguishability. We show that the dissipative nonequilibrium dynamics of this thermodynamic open quantum system can be reconstructed by correlation measurements under carefully mediated optical control. Comparing our findings with the traditional coherently pumped model, we find that the thermal pumping has the potential to generate nonclassical correlations resulting in photon indistinguishability, displaying an advantage in probing the nonequilibrium effects induced by the baths at different temperatures. Our work also demonstrates that incoherent pumping can optimize such correlations in output work beyond the classical limit. Lastly, we show that nonclassical correlations and resonant power at steady state cannot be simultaneously maximized in the weak coupling regime. Published by the American Physical Society 2024

DOI
10.1103/physrevresearch.6.023237

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We present a consistent optimization procedure for the optical measurements in open quantum systems using recently developed incoherent control protocol. Assigning an effective hot bath for the two-entangled-photon pump we recast the transmission of classical probe as a work in a quantum heat engine framework. We demonstrate that maximum work in such a heat engine can exceed that for the classical two-photon and one-photon pumps, while efficiency at maximum power can be attributed to conventional boundaries obtained for three-level maser heat engine. Our results pave the way for incoherent control and optimization of optical measurements in open quantum systems that involve two-photon processes with quantum light.
We present a consistent optimization procedure for the optical measurements in open quantum systems using recently developed incoherent control protocol. Assigning an effective hot bath for the two-entangled-photon pump we recast the transmission of classical probe as a work in a quantum heat engine framework. We demonstrate that maximum work in such a heat engine can exceed that for the classical two-photon and one-photon pumps, while efficiency at maximum power can be attributed to conventional boundaries obtained for the three-level maser heat engine. Our results pave the way for incoherent control and optimization of optical measurements in open quantum systems that involve two-photon processes with quantum light.
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We consider a recently proposed four-level quantum heat engine (QHE) model to analyze the role of quantum coherences in determining the thermodynamic properties of the engine, such as flux, output power, and efficiency. A quantitative analysis of the relative effects of the coherences induced by the two thermal baths is brought out. By taking account of the dissipation in the cavity mode, we define useful work obtained from the QHE and present some analytical results for the optimal values of relative coherences that maximizes flux (hence output power) through the engine. We also analyze the role of quantum effects in inducing population inversion (lasing) between the states coupled to the cavity mode. The universal behavior of the efficiency at maximum power (EMP\mathrm{EMP}EMP) is examined. In accordance with earlier theoretical predictions, to leading order, we find that $\mathrm{EMP}\ensuremath{\sim}{\ensuremath{\eta}}_{c}/2$, where ${\ensuremath{\eta}}_{c}$ is Carnot efficiency. However, the next higher order coefficient is system dependent and hence nonuniversal.
The single-atom version of the quantum heat engine based on electromagnetically induced transparency is theoretically investigated in this paper. In contact with a hot and a cold bath, the atom trapped in an optical cavity is coherently coupled by a coherent field, thus generating photons as output through a process that mimics a heat engine. Using semiclassical theory, we obtain the conditions for the classical gain parameter being positive. Then by taking a full quantum approach, we discuss the statistical property of the generated photons depicted by the photon number distribution and Wigner function, and show that it can be effectively tuned by the coupling field. Investigations on the energy and entropy balances of the heat engine process lead to an interesting result that the power of the engine is simply the energy per time provided by the hot reservoir. The coupling field plays a critical role in supporting the heat-engine process. However, the energy that it provides is all dumped into the cold reservoir. The total energy exchange conforms to the first law of thermodynamics. The efficiency of the engine depends on the temperatures of the two reservoirs and the strength of the coupling field. The entropy change of the heat-engine process suggests that when working far above the threshold of lasing, the efficiency approaches that of its atomic-ensemble-based partner.
Conventional continuous quantum heat engines with incoherent heat transfer perform poorly as they exploit two-body interactions between the system and hot or cold baths, thus having limited capability to outperform their classical counterparts. We introduce distinct continuous quantum heat engines that utilize coherent heat transfer with baths, yielding genuine quantum enhancement in performance. These coherent engines consist of one qutrit system and two photonic baths and enable coherent heat transfer via two-photon transitions involving three-body interactions between the system and hot and cold baths. We demonstrate that coherent engines deliver significantly higher power output with much greater reliability, i.e., lower signal-to-noise ratio of the power, by hundreds of folds over their incoherent counterparts. Importantly, coherent engines can operate close to or at the maximal achievable reliability allowed by the quantum thermodynamic uncertainty relation. Moreover, coherent engines manifest more nonclassical features than incoherent engines because they violate the classical thermodynamic uncertainty relation by a greater amount and for a wider range of parameters. These genuine enhancements in the performance of coherent engines are directly attributed to their capacity to harness higher energetic coherence for the resonant driving case. The experimental feasibility of coherent engines and the improved understanding of how quantum properties can enhance performance may find applications in quantum enabled technologies.