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- 摘要
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- 实验方案
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Coupled 3D master equation and 1D drifta??diffusion approach for advanced OLED modeling
摘要： A novel simulation approach for excitonic organic light-emitting diodes (OLEDs) is established by combining a continuous one-dimensional (1D) drift-diffusion (DD) model for the charge carrier dynamics with a three-dimensional (3D) master equation (ME) model describing the exciton dynamics in a multi-layer OLED stack with an additional coupling to a thin-film optics solver. This approach effectively combines the computational efficiency of the 1D DD solver with the physical accuracy of a discrete 3D ME model, where excitonic long-range interactions for energy transfer can be taken into account. The coupling is established through different possible charge recombination types as well as the carrier densities themselves. We show that such a hybrid approach can efficiently and accurately describe steady-state and transient behavior of optoelectronic devices reported in literature. Such a tool will facilitate the optimization and characterization of multilayer OLEDs and other organic semiconductor devices.
关键词： drift-diffusion,excitons,master equation,OLED
更新于2025-09-23 15:21:01
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Thermodynamic consistency of the optomechanical master equation
摘要： We investigate the thermodynamic consistency of the master equation description of heat transport through an optomechanical system attached to two heat baths, one optical and one mechanical. We employ three different master equations to describe this scenario: (i) The standard master equation used in optomechanics, where each bath acts only on the resonator that it is physically connected to; (ii) the so-called dressed-state master equation, where the mechanical bath acts on the global system; and (iii) what we call the global master equation, where both baths are treated nonlocally and affect both the optical and mechanical subsystems. Our main contribution is to demonstrate that, under certain conditions including when the optomechanical coupling strength is weak, the second law of thermodynamics is violated by the first two of these pictures. In order to have a thermodynamically consistent description of an optomechanical system, therefore, one has to employ a global description of the effect of the baths on the system.
关键词： heat transport,thermodynamics,second law of thermodynamics,optomechanics,master equation
更新于2025-09-23 15:21:01
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Coherent phonon lasing in a thermal quantum nanomachine
摘要： The notion of nanomachines has recently emerged to engage and use collective action of ensembles of nanoscale components or systems. Here we present a heat-gradient driven nanomachine concept which through appropriate coupling between quantum nanosystems is capable of realizing and maintaining an inversion. Based on a Lindblad form of the quantum master equation with a semiclassical coupling to the lattice displacement phonon field we show that this positive inversion can be harnessed to generate coherent optomechanical oscillations and phonon lasing.
关键词： heat-gradient,nanomachines,quantum nanosystems,quantum master equation,Lindblad form,phonon lasing
更新于2025-09-23 15:21:01
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Quantum Teleportation Under Different Collective Noise Environment
摘要： We investigate that the average fidelity of the standard quantum teleportation communication protocol when the quantum channel is affected by different local collective noise environments frequently encountered in real quantum communication protocol. We show that the quantum teleportation efficiency can be enhanced when the noise is unavoidable by choose the fit Bell state as the quantum channel, especially we can get perfect quantum teleportation efficiency under the local collective Pauli σy noise environment. Our work can shed some light on the application of practical standard quantum teleportation communication protocol.
关键词： Quantum teleportation,Quantum noise environment,Quantum master equation,Average fidelity
更新于2025-09-23 15:21:01
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-matrix based master equation for Coulomb drag in double quantum dots
摘要： Recently, novel Coulomb drag mechanisms in capacitively coupled double quantum dots were uncovered by the T -matrix based master equation (TME). The TME is so far the primary approach to studying Coulomb drag in the weak-coupling regime; however, its accuracy and reliability remain unexplored. Here, we evaluate the performance of the TME for Coulomb drag via a comparison with numerically exact results obtained by the hierarchical equation-of-motion approach. We ?nd that the TME can capture qualitative current evolutions versus dot levels, temperature, and effective coupling strengths but only partially succeeds at the quantitative level. Speci?cally, the TME gives highly inaccurate drag currents when large charge ?uctuations on dots exist and the fourth-order tunneling processes make a leading-order contribution. This failure of the TME is attributed to the combined effect of the unique drag mechanisms and its overlook of the fourth-order single-electron tunnelings. We identify the reliable regions to facilitate further quantitative studies on Coulomb drag by the TME.
关键词： weak-coupling regime,Coulomb drag,double quantum dots,T-matrix based master equation,hierarchical equation-of-motion approach
更新于2025-09-23 15:19:57
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Lasing in a coupled hybrid double quantum dot-resonator system
摘要： We theoretically investigate the possibility of lasing in an electromagnetic resonator coupled to a voltage-biased hybrid double quantum dot comprised of a double quantum dot tunnel coupled simultaneously to a normal metal and a superconducting lead. Using a unitary transformation, we derive a resonator-double quantum dot interaction Hamiltonian in the rotating-wave approximation which reveals the fact that lasing in this system is mediated by electron transitions between Andreev energy levels in the system’s density of states. Moreover, by employing a Markovian master equation incorporating dissipation effects for the electronic and photonic degrees of freedom, we numerically calculate the steady-state reduced density matrix of the system from which we determine the average photon number and its statistics in the resonator in various parameter regimes. We ?nd that at some appropriate parameter con?gurations, lasing can be considerably enhanced due to the possibility of electron transitions between multiple Andreev levels in the system.
关键词： lasing,Andreev energy levels,hybrid double quantum dot,electromagnetic resonator,Markovian master equation
更新于2025-09-23 15:19:57
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Qubit-assisted squeezing of mirror motion in a dissipative cavity optomechanical system
摘要： In this study, we investigate a hybrid system consisting of an atomic ensemble trapped inside a dissipative optomechanical cavity assisted with perturbative oscillator-qubit coupling. Such a system is generally very suitable for generating stationary squeezing of the mirror motion in the long-time limit under the unresolved sideband regime. Based on the master equation and covariance matrix approaches, we discuss in detail the respective squeezing effects. We also determine that in both approaches, simplifying the system dynamics with adiabatic elimination of the highly dissipative cavity mode is very effective. In the master equation approach, we find that the squeezing is a resulting effect of the cooling process and is robust against thermal fluctuations of the mechanical mode. In the covariance matrix approach, we can approximately obtain the analytical result of the steady-state mechanical position variance from the reduced dynamical equation. Finally, we compare the two approaches and observe that they are completely equivalent for the stationary dynamics. Moreover, the scheme may be useful for possible ultraprecise quantum measurement that involves mechanical squeezing.
关键词： master equation,mechanical squeezing,covariance matrix
更新于2025-09-19 17:15:36
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Dynamical Properties of the Finite-size Dicke Model Coupled to a Thermal Reservoir
摘要： We investigate the dynamical properties of the finite-size Dicke model coupled to a photon reservoir in the dispersive regime. The system–reservoir coupling in our Hamiltonian includes counter-rotating terms, which are relevant in the strong atom–cavity coupling. Because the dispersive regime is considered, the dynamics of low-energy states are described sufficiently accurately within the finite-dimensional subspace of the dressed states. Using the separation of the time scales between the system and the reservoir, we derive the Markovian quantum master equation in the subspace without ignoring the counter-rotating terms. The temporal evolution of the expectation of the cavity mode shows that the bifurcation of the long-lived state corresponds to the superradiant transition in the isolated model. The master equation explicitly gives the steady state solution. The numerical results for the first-order correlation function on the steady state indicate that the strong atom–cavity coupling enhances the coherence and softens the dephasing in the superradiant region.
关键词： dephasing,coherence,quantum master equation,superradiant transition,Dicke model
更新于2025-09-16 10:30:52
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The interplay of electron-photon and cavity-environment coupling on the electron transport through a quantum dot system
摘要： We theoretically investigate the characteristics of the electron transport through a two-dimensional a quantum dot system in the xy-plane coupled to a photon cavity and a photon reservoir, the environment. The electron-photon coupling, gγ, and the cavity-reservoir coupling, κ, are tuned to study the system in the weak, gγ ≤ κ, and the strong coupling regime, gγ > κ. An enhancement of current is both seen with increasing gγ and κ in the weak coupling regime for both x- and y-polarization of the photon field. This is a direct consequence of the Purcell effect. The current enhancement is due to the contribution of the photon replica states to the electron transport in which intraband transitions play an important role. The properties of the electron transport are drastically changed in the strong coupling regime with an x-polarized photon field in which the current is suppressed with increasing gγ, but it is still increasing with κ. This behavior of the current is related to the population of purely electronic states and depopulation of photon replica states.
关键词： Quantum master equation,Quantum Dot,Cavity-Quantum electrodynamics,Quantum transport,Purcell effect
更新于2025-09-16 10:30:52
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Single atom laser in normal-superconductor quantum dots
摘要： We study a single-level quantum dot strongly coupled to a superconducting lead and tunnel coupled to a normal electrode which can exchange energy with a single-mode resonator. We show that such a system implements a single atom laser. We employ both a semiclassical treatment and a quantum master-equation approach to characterize the properties of this laser. In particular, we ?nd that this system can be operated with ef?ciency approaching unity; that is, a single photon is emitted into the cavity for every Cooper pair participating in the charge current. We ?nd also that lasing in the proposed setup is clearly identi?able in the transport properties: in the lasing state, the electrical current through the quantum dot is pinned to the maximum value achievable in this hybrid nanostructure, and hence, the onset of lasing can be detected simply by a current measurement.
关键词： semiclassical treatment,quantum dot,Cooper pair,transport properties,superconducting lead,charge current,single atom laser,quantum master-equation approach,single-mode resonator,normal electrode
更新于2025-09-12 10:27:22