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Quantum heat engine with long-range advantages
Long-range interacting quantum devices provides a promising route for quantum technology applications. Here, the presence of long-range interactions is shown to enhance the performances of a quantum heat engine featuring a many-body working substance. We focus on the paradigmatic example of a Kitaev chain undergoing a quantum Otto cycle and show that a substantial thermodynamic advantage may be achieved as the range of the interactions among its constituents increases. The advantage is most significant for the realistic situation of a finite time cycle: the presence of long-range interactions reduces the non-adiabatic energy losses, by suppressing the detrimental effects of dynamically generated excitations. This effect allows mitigating the trade-off between power and efficiency, paving the way for a wide range of experimental and technological applications.
Journal Article
The case of the stinky stench
Inspector Croissant needs the help of Lady Pancake and Sir French Toast to investigate a terrible odor coming from the refrigerator.
BOOK
Boosting the performance of small autonomous refrigerators via common environmental effects
We explore the possibility of enhancing the performance of small thermal machines by the presence of common noise sources. In particular, we study a prototypical model for an autonomous quantum refrigerator comprised by three qubits coupled to thermal reservoirs at different temperatures. Our results show that engineering the coupling to the reservoirs to act as common environments lead to relevant improvements in the performance. The enhancements arrive to almost double the cooling power of the original fridge without compromising its efficiency. The greater enhancements are obtained when the refrigerator may benefit from the presence of a decoherence-free subspace. The influence of coherent effects in the dissipation due to one- and two-spin correlated processes is also examined by comparison with an equivalent incoherent yet correlated model of dissipation.
Journal Article
Coherence-assisted single-shot cooling by quantum absorption refrigerators
The extension of thermodynamics into the quantum regime has received much attention in recent years. A primary objective of current research is to find thermodynamic tasks which can be enhanced by quantum mechanical effects. With this goal in mind, we explore the finite-time dynamics of absorption refrigerators composed of three quantum bits (qubits). The aim of this finite-time cooling is to reach low temperatures as fast as possible and subsequently extract the cold particle to exploit it for information processing purposes. We show that the coherent oscillations inherent to quantum dynamics can be harnessed to reach temperatures that are colder than the steady state in orders of magnitude less time, thereby providing a fast source of low-entropy qubits. This effect demonstrates that quantum thermal machines can surpass classical ones, reminiscent of quantum advantages in other fields, and is applicable to a broad range of technologically important scenarios.
Journal Article
Four-Function Fully Automatic Refrigerator Protection System Design
In the automatic refrigerator protection system hardware design, the MCU is selected as the core control of the system, the specific design content includes the selection of the automatic refrigerator protection system design scheme, MCU, and sensor types and models, in addition, it is necessary to combine the components of the display module design; In the system software design, the most core content is the system program design. The system collects the undervoltage, overvoltage, power failure, leakage, and other conditions of the power supply refrigerator, and the control switch is automatically disconnected to protect the refrigerator. C language was chosen to design the system software code, and Proteus software was used to realize the system function simulation, and the functions of the system were verified.
Journal Article
Non-equilibrium dynamics of quantum absorption refrigerator at Liouvillian exceptional points: critical damping and better performance
We explore how Liouvillian exceptional points (LEPs) shape the non-equilibrium dynamics and performance of a three-level quantum absorption refrigerator (QAR). While most studies focus on steady-state operation, we demonstrate that the non-equilibrium dynamics near LEPs play a crucial role. At third-order LEPs, we derive the conditions for critical damping, which leads to the fastest convergence of both the system state and heat currents. Remarkably, non-equilibrium contributions can enhance heat transfer from the cold to the hot bath at reduced work cost, yielding a higher coefficient of performance (COP). By tuning the relative weights of these contributions, we demonstrate a strategy to optimize QAR performance focusing on the initial heat current from the cold bath. The influence of the non-equilibrium process is inevitable and accumulates, resulting in a larger total heat absorption and a higher accumulated COP than in the equilibrium case. These results highlight LEPs as a resource for accelerating relaxation and enhancing efficiency, offering practical guidance for the design of high-performance quantum thermal machines.
Journal Article
Equivalence of Quantum Heat Machines, and Quantum-Thermodynamic Signatures
Quantum heat engines (QHE) are thermal machines where the working substance is a quantum object. In the extreme case, the working medium can be a single particle or a few-level quantum system. The study of QHE has shown a remarkable similarity with macroscopic thermodynamical results, thus raising the issue of what is quantum in quantum thermodynamics. Our main result is the thermodynamical equivalence of all engine types in the quantum regime of small action with respect to Planck’s constant. They have the same power, the same heat, and the same efficiency, and they even have the same relaxation rates and relaxation modes. Furthermore, it is shown that QHE have quantum-thermodynamic signature; i.e., thermodynamic measurements can confirm the presence of quantum effects in the device. We identify generic coherent and stochastic work extraction mechanisms and show that coherence enables power outputs that greatly exceed the power of stochastic (dephased) engines.
Journal Article
Quantum thermal machines and batteries
The seminal work by Sadi Carnot in the early nineteenth century provided the blueprint of a reversible heat engine and the celebrated second law of thermodynamics eventually followed. Almost two centuries later, the quest to formulate a quantum theory of the thermodynamic laws has thus unsurprisingly motivated physicists to visualize what are known as ‘quantum thermal machines’ (QTMs). In this article, we review the prominent developments achieved in the theoretical construction as well as understanding of QTMs, beginning from the formulation of their earliest prototypes to recent models. We also present a detailed introduction and highlight recent progress in the rapidly developing field of ‘quantum batteries’.
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Journal Article
Torsional refrigeration by twisted, coiled, and supercoiled fibers
Higher-efficiency, lower-cost refrigeration is needed for both large- and small-scale cooling. Refrigerators using entropy changes during cycles of stretching or hydrostatic compression of a solid are possible alternatives to the vapor-compression fridges found in homes. We show that high cooling results from twist changes for twisted, coiled, or supercoiled fibers, including those of natural rubber, nickel titanium, and polyethylene fishing line. Using opposite chiralities of twist and coiling produces supercoiled natural rubber fibers and coiled fishing line fibers that cool when stretched. A demonstrated twist-based device for cooling flowing water provides high cooling energy and device efficiency. Mechanical calculations describe the axial and spring-index dependencies of twist-enhanced cooling and its origin in a phase transformation for polyethylene fibers.
Journal Article