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arXiv:2101.11936 · Physical Review Applied

Photonic Heat Rectification in a System of Coupled Qubits

A. Iorio, E. Strambini, G. Haack, M. Campisi, F. Giazotto

Published May 21, 2021• 36 citations
arXivHTMLPDF

Abstract

We theoretically investigate a quantum heat diode based on two interacting flux qubits coupled to two heat baths. Rectification of heat currents is achieved by asymmetrically coupling the qubits to the reservoirs, which are modeled as dissipative $RLC$ resonators. We find that the coherent interaction between the qubits can be exploited to enhance the rectification factor, which otherwise would be constrained by the temperatures and couplings of the baths. Remarkably high values of the rectification ratio, up to $\mathcal{R}\ensuremath{\sim}3.5$, can be obtained for realistic system parameters, with an enhancement up to approximately $230\mathrm{%}$ compared to the noninteracting case. The system features the possibility of manipulating both the rectification amplitude and direction, allowing for an enhancement or suppression of the heat flow to a chosen bath. For the parameter regime in which rectification is maximized, we find a significant increase of the rectification above a critical interaction value, which corresponds to the onset of a nonvanishing entanglement in the system. Finally, we discuss the dependence of the rectification factor on the bath temperatures and couplings.

DOI
10.1103/physrevapplied.15.054050

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A qubit-oscillator junction connecting as a series two bosonic heat baths at different temperatures can display heat valve and diode effects. In particular, the rectification can change in magnitude and even in sign, implying an inversion of the preferential direction for the heat current with respect to the temperature bias. We perform a systematic study of these effects in a circuit QED model of qubit-oscillator system and find that the features of current and rectification crucially depend on the qubit-oscillator coupling. While at small coupling, transport occurs via a resonant mechanism between the subsystems, in the ultrastrong coupling regime the junction is a unique, highly hybridized system and current becomes largely insensitive to the detuning. Correspondingly, the rectification undergoes a change of sign. In the nonlinear transport regime, the coupling strength determines whether the current scales sub- or superlinearly with the temperature bias and whether the rectification, which increases in magnitude with the bias, is positive or negative. We also find that steady-state coherence largely suppresses the current and enhances rectification. An insight on these behaviors with respect to changes in the system parameters is provided by analytical approximate formulas.
We put forward a quantum-optical model for a thermal diode based on heat transfer between two thermal baths through a pair of interacting qubits. We find that if the qubits are coupled by a Raman field that induces an anisotropic interaction, heat flow can become nonreciprocal and undergoes rectification even if the baths produce equal dissipation rates of the qubits, and these qubits can be identical, i.e., mutually resonant. The heat flow rectification is explained by four-wave mixing and Raman transitions between dressed states of the interacting qubits and is governed by a global master equation. The anisotropic two-qubit interaction is the key to the operation of this simple quantum thermal diode, whose resonant operation allows for high-efficiency rectification of large heat currents. Effects of spatial overlap of the baths are addressed. We discuss the possible realizations of the model in various platforms, including optomechanical setups, systems of trapped ions, and circuit QED.
We present a quantum thermal diode model based on a coupled qutrit–qubit system designed to control heat flow between two thermal baths with unprecedented efficiency. This differs from previous models in terms of the asymmetry introduced by spin particles and their interaction. By exploiting the interactions between degenerate states within the coupled qutrit–qubit system, our model demonstrates diode-like behavior that is both robust and energy-efficient. Utilizing the frameworks of open quantum systems and the quantum Markovian master equation, with the Born and rotating wave approximations, we comprehensively analyze the system’s behavior. Numerical simulations reveal significant thermal rectification across a wide temperature range, positioning our model as a groundbreaking solution for nanoscale heat management. In addition, we employ state transition diagrams to elucidate the transition rate characteristics that underpin the diode behavior. Finally, we explore the potential for physical implementation using superconducting circuits, highlighting the practical relevance of our design.
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Nonequilibrium heat transport and quantum thermodynamics in light-matter interacting systems have received increasing attention. Quantum thermal devices, e.g., heat valve and head diode, have been realized. Recently, it has been discovered that the anisotropic light-matter interactions can greatly modify the eigenvalues and eigenvectors of hybrid quantum systems, leading to nontrivial quantum phase transitions, quantum metrology, and nonclassicality of photons. To explore the influences of anisotropic light-matter interactions on quantum transport, we investigate heat flow in the nonequilibrium anisotropic Dicke model. In this model, an ensemble of qubits collectively interacts with an anisotropic photon field. Each component interacts with bosonic thermal reservoirs. Quantum dressed master equation (DME) is included to properly study dissipative dynamics of the anisotropic Dicke model. Within the eigenbasis of the reduced anisotropic Dicke system, strong qubit-photon couplings can be properly handled. Our results demonstrate that anisotropic qubit-photon interactions are crucial for modulating steady-state heat flow. In particular, it is found that under strong coupling the heat flow is dramatically suppressed by a large anisotropic qubit-photon factor. While under moderate coupling, the anisotropic qubit-photon interactions enhance the heat flow. Moreover, the increase in the number of qubits amplifies the flow characteristics, with the peaks increasing and the valleys decreasing. Besides, we derive two analytical expressions of heat flows in thermodynamic limit approximation with limiting anisotropic factors. These heat currents exhibit the cotunneling heat transport pictures. They also serve as the upper boundaries for the heat flows in the finite-size anisotropic Dicke model. We also analyze the thermal rectification effect in the anisotropic Dicke model.
Abstract A quantum thermal diode based on strong dispersive coupling between a magnon and a qubit is proposed and analysed. The system utilizes a direct dispersive interaction that leads to asymmetric energy transitions, enabling controllable directional heat flow. Detailed numerical simulations demonstrate the occurrence of nearly perfect rectification under appropriate parameter conditions, with the rectification factor approaching unity in both resonant and off-resonant regimes. Results reveal that factors such as coupling strength, magnon anisotropy, and energy detuning significantly influence both heat current and rectification performance. While increased dispersive coupling enhances both heat transfer and rectification efficiency, purely coherent or combined coupling configurations are shown to degrade performance. Comparative analysis with existing thermal diode models highlights the superior performance of the proposed system, especially its ability to achieve nearly perfect rectification while maintaining appreciable heat currents. This work presents a feasible platform for designing efficient quantum heat management devices.