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arXiv:2208.12620 · Entropy

Quantum Thermal Amplifiers with Engineered Dissipation

Antonio Mandarino

Published Jul 26, 2022• 6 citations
arXivHTMLPDF

Abstract

A three-terminal device, able to control the heat currents flowing through it, is known as a quantum thermal transistor whenever it amplifies two output currents as a response to the external source acting on its third terminal. Several efforts have been proposed in the direction of addressing different engineering options of the configuration of the system. Here, we adhere to the scheme in which such a device is implemented as a three-qubit system that interacts with three separate thermal baths. However, another interesting direction is how to engineer the thermal reservoirs to magnify the current amplification. Here, we derive a quantum dynamical equation for the evolution of the system to study the role of distinct dissipative thermal noises. We compare the amplification gain in different configurations and analyze the role of the correlations in a system exhibiting the thermal transistor effect, via measures borrowed from the quantum information theory.

DOI
10.3390/e24081031

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•Aug 11, 2026•0 citations
A three-terminal device, able to control the heat currents flowing through it, is known as a quantum thermal transistor whenever it amplifies two output currents as a response to the external source acting on its third terminal. Several efforts have been proposed in the direction of addressing different engineering options of the configuration of the system. Here, we adhere to the scheme in which such a device is implemented as a three-qubit system that interacts with three separate thermal baths. However, another interesting direction is how to engineer the thermal reservoirs to magnify the current amplification. Here, we derive a quantum dynamical equation for the evolution of the system to study the role of distinct dissipative thermal noises. We compare the amplification gain in different configurations and analyze the role of the correlations in a system exhibiting the thermal transistor effect, via measures borrowed from the quantum information theory.
A quantum thermal transistor is designed by the strong coupling between one qubit and one qutrit which are in contact with three heat baths with different temperatures. The thermal behavior is analyzed based on the master equation by both the numerical and the approximately analytic methods. It is shown that the thermal transistor, as a three-terminal device, allows a weak modulation heat current (at the modulation terminal) to switch on and off and effectively modulate the heat current between the other two terminals. In particular, the weak modulation heat current can induce the strong heat current between the other two terminals with the multiple-region amplification of heat current. Furthermore, the heat currents are quite robust to the temperature (current) fluctuation at the lower-temperature terminal within a certain range of temperature, and so it can behave as a heat current stabilizer.
We study a quantum system composed of three interacting qubits, each coupled to a different thermal reservoir. We show how to engineer it to build a quantum device analogous to an electronic bipolar transistor. We outline how the interaction among the qubits plays a crucial role for the appearance of the effect, also linking it to the characteristics of system-bath interactions that govern the decoherence and dissipation mechanisms of the system. By comparison with previous proposals, our model extends the regime of parameters where the transistor effect occurs, the effect being more robust with respect to small variations of the coupling parameters. Moreover, our model appears to be more realistic and directly connected in terms of potential implementations to feasible setups in the domain of quantum spin chains, such as molecular nanomagnets.
Quantum thermal transistor is a microscopic thermodynamical device that can modulate and amplify heat current through two terminals by the weak heat current at the third terminal. Here we study the common environmental effects on a quantum thermal transistor made up of three strong-coupling qubits. It is shown that the functions of the thermal transistor can be maintained and the amplification rate can be modestly enhanced by the skillfully designed common environments. In particular, the presence of a dark state in the case of the completely correlated transitions can provide an additional external channel to control the heat currents without any disturbance of the amplification rate. These results show that common environmental effects can offer new insights into improving the performance of quantum thermal devices.
Quantum heat transport governs energy exchange processes and statistical laws in non-equilibrium quantum systems, and plays a pivotal role in quantum thermodynamics. We investigate the steady-state thermal transport of a noncommuting coupled spin system. We employ the quantum dressed master equation approach within the framework of open quantum system theory to accurately analyze the non-equilibrium dynamics, ensuring the validity of transport results in the strong coupling regime. Our results demonstrate that noncommuting spin coupling serves as a significant resource for modulating the nonlinearity of the heat current. Specifically, in the weak spin-coupling regime, the system exhibits robust negative differential thermal conductance (NDTC) across various spin numbers. By deriving analytical expressions for the heat current in both the single-spin and large-spin limits, we reveal that this NDTC behavior is governed by microscopic cycle fluxes. Physically, this arises because spin excitation channels induced by the cold reservoir are suppressed under a large temperature bias, thereby blocking energy exchange cycles. Conversely, in the strong spin-coupling and large temperature bias regime, the quantum system demonstrates pronounced thermal rectification. This high rectification efficiency originates from the unidirectional saturation of the heat current, rendering the system a promising candidate for high-performance thermal diodes. Furthermore, we extend the model to a three-terminal configuration to construct a quantum thermal transistor. By manipulating the temperature of the gate reservoir, we achieve efficient modulation and amplification of heat flow between the source and drain. The heat amplification factor is shown to far exceed unity in specific operating regions, confirming significant thermal amplification.
Abstract We investigate the performance of a three-qubits quantum thermal transistor using coarse-graining, global, and local master equations, respectively. Special attention is paid to the validity of the three methods in different internal coupling strengths. The effects of system and bath parameters on the amplification effect are studied. It is found that small middle qubit frequency, weak internal coupling, and symmetric configuration of system-bath coupling lead to large amplification factor. The heat current amplification mechanism is discussed and quantum coherence does not contribute to amplification. Besides, the thermal transistor is realized by tuning the temperature of the middle bath, the temperature of the left bath, or the internal coupling strength.
Quantum thermal field effect transistor (qtFET) composed of left-qubit, middle-qutrit, and right-qubit subsystems has been proposed and extensively analysed. In this architecture, the left qubit is coupled to the middle qutrit, which in turn interacts with the right qubit. Each subsystem interacts independently with its respective baths. The middle subsystem serves as a modulator. We have shown that the qtFET exhibits functionality analogous to that of a conventional electronic field effect transistor (eFET). The left, right, and middle subsystems of the qtFET correspond to the drain, source, and gate of an eFET in a common gate configuration, respectively. Our results show that the qtFET can precisely modulate thermal currents, highlighting its potential as a fundamental building block for quantum thermal devices and amplifiers in emerging quantum technologies. This qtFET can be used as a modulator in quantum systems with remarkable precision and can be used as a vital component in amplifiers to develop quantum devices. The integration of Bayesian optimization into the parameter optimization of quantum thermal devices has been demonstrated in this thesis. Bayesian optimization has been performed and used for parameter optimization of qtFET. qtFET has been developed to function as amplifier using optimized parameters in an analogous way to an eFET behaves as amplifier. The transconductance of qtFET has been achieved in order of ten thousands using extended search space range, while performing parameter optimization using Bayesian optimization. The amplification factor is taken as the ratio of gate transconductance and differential conductance. Then the amplification factor is optimized using extended upper bound of search space range of coupling strengths, dissipation rates, and energy levels of subsystem of qtFET which resulted in amplification factor in order of ten millions. This qtFET has been developed to detect variations in temperature at the nanoscale (10−910^{-9}10−9) using optimized parameters. In this work, a heatmap depicting the variation of the thermal current as function of middle bath temperature and interaction strength between middle and right subsystem of qtFET has been verified using first law of thermodynamics. Finally, the negative differential thermal resistance (NDTR) has been found to verify the optimized amplification factor results of qtFET in this work.