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arXiv:2302.09948

Experimental demonstration of quantum cooling engine powered by entangled measurement

Ning-Ning Wang, Huan Cao, Chao Zhang, Xiao‐Ye Xu, Bi‐Heng Liu, Yun-Feng Huang, Chuan‐Feng Li, Guang‐Can Guo

Published Feb 20, 2023• 0 citations
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Abstract

Traditional refrigeration is driven either by external force or an information-feedback mechanism. Surprisingly, the quantum measurement and collapse, which are generally detrimental, can also be used to power a cooling engine even without requiring any feedback mechanism. In this work, we experimentally demonstrate quantum measurement cooling (QMC) powered by entangled measurement by using a novel linear optical simulator. In the simulator, different thermodynamic processes can be simulated by adjusting the energy-level spacing of working substance and the temperature of thermal bath. We show experimentally that, without prior knowledge about the measurement to be made, QMC remains likely to occur. We also demonstrate that QMC is robust against measurement noise. Those experimental results show that quantum measurement is not always detrimental but can be a valuable thermodynamic resource.

DOI
10.48550/arxiv.2302.09948

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Traditional refrigeration is driven either by external force or an information-feedback mechanism. Surprisingly, the quantum measurement and collapse, which are generally detrimental, can also be used to power a cooling engine even without requiring any feedback mechanism. In this work, we experimentally demonstrate quantum measurement cooling (QMC) powered by entangled measurement by using a novel linear optical simulator. In the simulator, different thermodynamic processes can be simulated by adjusting the energy-level spacing of working substance and the temperature of thermal bath. We show experimentally that, without prior knowledge about the measurement to be made, QMC remains likely to occur. We also demonstrate that QMC is robust against measurement noise. Those experimental results show that quantum measurement is not always detrimental but can be a valuable thermodynamic resource.
Traditional refrigeration is driven either by external forces or by the information-feedback mechanism. Surprisingly, quantum measurement and collapse, typically viewed as detrimental, can also power a quantum cooling engine without requiring any feedback mechanism. In this work, we perform a proof-of-principle demonstration of quantum measurement cooling (QMC) powered by entangled measurements using a highly controllable linear optical simulator. The simulator can simulate qubits with different energy-level spacings and their thermalizing processes at different temperatures, and also allows for arbitrary projections of two qubits at different energy levels. We show the effect of changes in energy levels and measurement bases on the cooling process and demonstrate the robustness of QMC. These results reveal the special role of entangled measurements in quantum thermodynamics, indicate that quantum measurement is not always detrimental but can be a valuable thermodynamic resource. Our setup also offers a highly controllable simulation platform for multiqubit quantum engines.
Invasiveness of quantum measurements is a genuinely quantum mechanical feature that is not necessarily detrimental: Here we show how quantum measurements can be used to fuel a cooling engine. We illustrate quantum measurement cooling (QMC) by means of a prototypical two-stroke two-qubit engine which interacts with a measurement apparatus and two heat reservoirs at different temperatures. We show that feedback control is not necessary for operation while entanglement must be present in the measurement projectors. We quantify the probability that QMC occurs when the measurement basis is chosen randomly, and find that it can be very large as compared to the probability of extracting energy (heat engine operation), while remaining always smaller than the most useless operation, namely, dumping heat in both baths. These results show that QMC can be very robust to experimental noise. A possible low-temperature solid-state implementation that integrates circuit QED technology with circuit quantum thermodynamics technology is presented.
Quantum tunneling allows electrons to be transferred between two regions separated by an energetically forbidden barrier. Performing a position measurement that finds a particle in the barrier forces the tunneling electrons to transition from having a classically forbidden energy to an energy above the barrier height. We exploit this effect to define quantum tunneling engines that can use the unconditioned detection of virtually occupied states as a resource for power generation and cooling. Leveraging energy exchange with the detector, we show that the device can operate in a hybrid regime, enabling simultaneous cooling and power generation. Furthermore, we demonstrate measurement-assisted autonomous refrigeration and "checkpoint" cooling driven purely by a thermal bias, without the need for an applied potential. We also find a "purification-by-noise" effect when the measurement drives the system into a stationary dark state. These results underscore the intriguing dual role of measurement as a thermodynamic resource and a dark state generator.
We investigate a quantum Otto engine (QOE) constructed from the two-qubit quantum Rabi model, operating within a cavity quantum electrodynamics (QED) architecture. The engine operates with two qubits as the working substance and a single non-Markovian hot thermal bath, modeled via the hierarchical equations of motion (HEOM) formalism. In place of a conventional cold thermal reservoir, the cooling stroke is realized through a projective measurement protocol on the cavity mode, which acts as an ancillary subsystem and effectively mimics a cold bath for the qubit working medium via measurement back-action. A squeezing drive applied to the cavity mode serves as a quantum fuel. We demonstrate that cavity squeezing systematically enhances both the power output and operational efficiency of the engine - the work extracted per unit of heat drawn from the hot bath-driving it above the standard quantum Otto limit. In the limit-cycle regime, the efficiency, while remaining above the Otto bound throughout, asymptotically converges to it from above. This identifies squeezing as a controllable quantum resource for thermodynamic optimization. Our results reveal that the interplay between qubit-cavity coupling, measurement-induced cooling, and non-equilibrium squeezing gives rise to a multi-resource thermodynamic architecture with performance characteristics inaccessible to conventional two-bath quantum Otto engines, thereby providing a concrete route toward experimentally realizable quantum heat engines in cavity QED platforms.
We propose quantum engines powered entirely by a position-resolving measurement performed on a quantum particle. These engines produce work by moving the quantum particle against a force. Unlike classical information-driven engines (e.g., Maxwell's demon), the energy is not extracted from a thermal hot source but directly from the observation process via a partial wave-function collapse of the particle. We present results for the work done and the efficiency for different values of the engine parameters. Feedback is required for optimal performance. We find that unit efficiency can be approached when one measurement outcome prepares the initial state of the next engine cycle, while the other outcomes leave the original state nearly unchanged.
Quantum fluctuations, which result from the Heisenberg uncertainty principle, explain a number of physical observations, from the finite mass of elementary particles to the Lamb shift in hydrogen and the Casimir effect. The local violation of the conservation of energy raises the question of whether the energy of quantum fluctuations can sustain the cycle of a quantum engine. So far, a proposal has hinted that this is possible, but contains important caveats. In this Letter, we predict that quantum fluctuations can power an autonomous spintronic quantum information engine by converting entanglement energy into useful electrical work. Our two-stroke engine operates on two entangled spin quantum dots (QDs) that are connected in series with two fully spin-polarized baths. The ultrafast measurement stroke breaks the entanglement, thereby energizing the system on average. This energy is released into the leads as electrical current when the thermalizing stroke equilibrates the QDs with the electrode baths. Using a master equation approach, we analytically demonstrate the efficiency of the quantum fluctuation-driven engine, and we study the cycle numerically to gain insight into the relevant parameters to maximize power. Our results suggest that quantum fluctuations and the measurement back-action alone cannot explain prior experimental results. Measuring the spin dynamics of the engine's ferromagnetic electrodes should help determine its efficiency. This electronically driven feedback on quantum entanglement should also boost quantum chemistry, biology and cognition.