Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNonequilibrium free energy and information flow of a double quantum-dot system with Coulomb coupling
75
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We build a double quantum-dot system with Coulomb coupling and aim at studying the connections among the entropy production, free energy, and information flow. By utilizing the concepts in stochastic thermodynamics and graph theory analysis, the Clausius and nonequilibrium free energy inequalities are built to interpret the local second law of thermodynamics for subsystems. A fundamental set of cycle fluxes and affinities is identified to decompose the two inequalities by using Schnakenbergs network theory. The results show that the thermodynamic irreversibility has the energy-related and information-related contributions. A global cycle associated with the feedback-induced information flow would pump electrons against the bias voltage, which implements a Maxwell Demon.
rate research
Read More
A definition of nonequilibrium free energy $mathcal{F}_{textsc{s}}$ is proposed for dynamical Gaussian quantum open systems strongly coupled to a heat bath and a formal derivation is provided by way of the generating functional in terms of the coarse-grained effective action and the influence action. For Gaussian open quantum systems exemplified by the quantum Brownian motion model studied here, a time-varying effective temperature can be introduced in a natural way, and with it, the nonequilibrium free energy $mathcal{F}_{textsc{s}}$, von Neumann entropy $mathcal{S}_{vN}$ and internal energy $mathcal{U}_{textsc{s}}$ of the reduced system ($S$) can be defined accordingly. In contrast to the nonequilibrium free energy found in the literature which references the bath temperature, the nonequilibrium thermodynamic functions we find here obey the familiar relation $mathcal{F}_{textsc{s}}(t)=mathcal{U}_{textsc{s}}(t)- T_{textsc{eff}} (t),mathcal{S}_{vN}(t)$ {it at any and all moments of time} in the systems fully nonequilibrium evolution history. After the system equilibrates they coincide, in the weak coupling limit, with their counterparts in conventional equilibrium thermodynamics. Since the effective temperature captures both the state of the system and its interaction with the bath, upon the systems equilibration, it approaches a value slightly higher than the initial bath temperature. Notably, it remains nonzero for a zero-temperature bath, signaling the existence of system-bath entanglement. Reasonably, at high bath temperatures and under ultra-weak couplings, it becomes indistinguishable from the bath temperature. The nonequilibrium thermodynamic functions and relations discovered here for dynamical Gaussian quantum systems should open up useful pathways toward establishing meaningful theories of nonequilibrium quantum thermodynamics.
The Jarzynski equality is one of the most influential results in the field of non equilibrium statistical mechanics. This celebrated equality allows to calculate equilibrium free energy differences from work distributions of nonequilibrium processes. In practice, such calculations often suffer from poor convergence due to the need to sample rare events. Here we examine if the inclusion of measurement and feedback can improve the convergence of nonequilibrium free energy calculations. A modified version of the Jarzynski equality in which realizations with a given outcome are kept, while others are discarded, is used. We find that discarding realizations with unwanted outcomes can result in improved convergence compared to calculations based on the Jarzynski equality. We argue that the observed improved convergence is closely related to Bennetts acceptance ratio method, which was developed without any reference to measurements or feedback.
We investigate the particle and heat transport in quantum junctions with the geometry of star graphs. The system is in a nonequilibrium steady state, characterized by the different temperatures and chemical potentials of the heat reservoirs connected to the edges of the graph. We explore the Landauer-Buettiker state and its orbit under parity and time reversal transformations. Both particle number and total energy are conserved in these states. However the heat and chemical potential energy are in general not separately conserved, which gives origin to a basic process of energy transmutation among them. We study both directions of this process in detail, introducing appropriate efficiency coefficients. For scale invariant interactions in the junction our results are exact and explicit. They cover the whole parameter space and take into account all nonlinear effects. The energy transmutation depends on the particle statistics.
We investigate the thermoelectric properties of a T-shaped double quantum dot system described by a generalized Anderson Hamiltonian. The systems electrical conduction (G) and the fundamental thermoelectric parameters such as the Seebeck coefficient ($S$) and the thermal conductivity ($kappa$), along with the systems thermoelectric figure of merit (ZT) are numerically estimated based on a Greens function formalism that includes contributions up to the Hartree-Fock level. Our results account for finite onsite Coulomb interaction terms in both component quantum dots and discuss various ways leading to an enhanced thermoelectric figure of merit for the system. We demonstrate that the presence of Fano resonances in the Coulomb blockade regime is responsible for a strong violation of the Wiedemann-Franz law and a considerable enhancement of the systems figure of merit ($ZT$).
Quantum coherence in solid-state systems has been demonstrated in superconducting circuits and in semiconductor quantum dots. This has paved the way to investigate solid-state systems for quantum information processing with the potential benefit of scalability compared to other systems based on atoms, ions and photons. Coherent coupling of superconducting circuits to microwave photons, circuit quantum electrodynamics (QED), has opened up new research directions and enabled long distance coupling of qubits. Here we demonstrate how the electromagnetic field of a superconducting microwave resonator can be coupled to a semiconductor double quantum dot. The charge stability diagram of the double dot, typically measured by direct current (DC) transport techniques, is investigated via dispersive frequency shifts of the coupled resonator. This hybrid all-solid-state approach offers the potential to coherently couple multiple quantum dot and superconducting qubits together on one chip, and offers a method for high resolution spectroscopy of semiconductor quantum structures.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
