We investigate how particle-hole symmetry, quantum interference, and tunnel barriers shape thermodynamic uncertainty relations in chaotic Andreev billiards. Using random-matrix theory and the Mahaux-Weidenmüller scattering approach, we study charge conductance and shot noise across the four Altland-Zirnbauer symmetry classes, from the single-channel extreme quantum limit to the multichannel semiclassical regime and from ideal to opaque contacts. We characterize thermodynamic precision through two complementary ensemble observables: either by averaging the sample-resolved noise-to-conductance ratio, or from the separately averaging noise and conductance. Their pronounced discrepancy in the extreme quantum regime reveals the non-self-averaging character of mesoscopic transport and persists over a broad range of barrier transparencies. For ideal contacts, the first provides a sensitive fingerprint of the Altland-Zirnbauer symmetry class. In the opaque regime, this hierarchy changes. Despite these strong symmetry- and barrier-dependent effects, the standard thermodynamic uncertainty relation remains satisfied throughout all regimes investigated. Our results establish thermodynamic uncertainty as a symmetry-sensitive probe of universal transport in chaotic normal-superconducting systems.
We investigate how particle-hole symmetry, quantum interference, and tunnel barriers shape thermodynamic uncertainty relations in chaotic Andreev billiards. Using random-matrix theory and the Mahaux-Weidenmüller scattering approach, we study charge conductance and shot noise across the four Altland-Zirnbauer symmetry classes, from the single-channel extreme quantum limit to the multichannel semiclassical regime and from ideal to opaque contacts. We characterize thermodynamic precision through two complementary ensemble observables: either by averaging the sample-resolved noise-to-conductance ratio, or from the separately averaging noise and conductance. Their pronounced discrepancy in the extreme quantum regime reveals the non-self-averaging character of mesoscopic transport and persists over a broad range of barrier transparencies. For ideal contacts, the first provides a sensitive fingerprint of the Altland-Zirnbauer symmetry class. In the opaque regime, this hierarchy changes. Despite these strong symmetry- and barrier-dependent effects, the standard thermodynamic uncertainty relation remains satisfied throughout all regimes investigated. Our results establish thermodynamic uncertainty as a symmetry-sensitive probe of universal transport in chaotic normal-superconducting systems.
Effect of electron-hole asymmetry on ΔT noise in metal/quantum point contact/metal and metal/quantum point contact/superconductor junctions
This work examines charge ΔT noise in two-terminal hybrid nanostructures featuring a quantum point contact (QPC), realized either between two normal metallic leads (NQN) or between a normal metal and a superconducting lead (NQS). The energy-dependent transmission of a QPC breaks electron-hole (e-h) symmetry, leading to a finite thermovoltage under an applied temperature and voltage bias. In contrast, in earlier studies on hybrid junctions incorporating insulating barriers, as electron-hole symmetry is preserved, have vanishing thermovoltage, and consequently, charge ΔT noise is calculated at zero thermovoltage. In our setup, the broken e-h symmetry allows for a finite thermovoltage, at which we compute the corresponding charge ΔT noise. Unlike earlier studies restricted by electron-hole symmetry and vanishing thermovoltage, our work establishes a self-consistent thermoelectric noise framework in mesoscopic hybrid junctions, revealing how Andreev reflection fundamentally reshapes charge ΔT noise once electron-hole symmetry is broken. This broad access to charge fluctuation signatures provides a more comprehensive understanding of non-equilibrium transport in linear response. To the best of our knowledge, this is the first work that systematically explores the interplay between Andreev reflection and electron-hole symmetry breaking in the context of quantum noise and ΔT noise in mesoscopic hybrid structures.
We study Andreev-mediated transport and current fluctuations in interacting normal-superconducting quantum-dot systems. Using a generalized master equation based on real-time diagrammatics and full counting statistics, we compute the steady-state current, zero-frequency noise, and rate of entropy production in the large superconducting-gap limit. We show how Coulomb interactions modify Andreev-mediated transport by renormalizing resonant conditions and suppressing superconducting coherence, leading to a pronounced reduction of current precision even when average currents are only weakly affected. These effects are particularly evident at high temperatures, where conventional Coulomb-blockade features are thermally smeared while fluctuation properties remain highly sensitive. By analyzing thermodynamic uncertainty relations, we demonstrate that violations of the quantum bound present in the noninteracting regime are progressively reduced and eventually suppressed as interactions increase, whereas the recently proposed hybrid bound remains satisfied. Our results clarify how Coulomb interactions, and nonequilibrium fluctuations jointly determine transport properties in hybrid superconducting devices, and establish current precision as a robust benchmark for interacting Andreev transport beyond the noninteracting limit.
Thermodynamic uncertainty relations (TURs) bound the precision of currents by entropy production, but quantum transport of noncommuting (non-Abelian) charges challenges standard formulations because different charge components cannot be monitored within a single classical frame. We derive a process-level matrix TUR starting from the operational entropy production Σ=D(ρSE′∥ρS′⊗ρE). Isolating the experimentally accessible bath divergence Dbath=D(ρE′∥ρE), we prove a fully nonlinear, saturable lower bound valid for arbitrary current vectors Δq: Dbath≥B(Δq,V,V′), where the bound depends only on the transported-charge signal Δq and the pre/post collision covariance matrices V and V′. In the small-fluctuation regime Dbath≥21ΔqTV−1Δq+O(∥Δq∥4), while beyond linear response it remains accurate. Numerical strong-coupling qubit collisions illustrate the bound and demonstrate near-saturation across broad parameter ranges using only local measurements on the bath probe.
Abstract We study the fluctuations of generic currents in multi-terminal, multi-channel coherent quantum transport settings. In the quantum regime, these fluctuations and the resulting precision differ strongly depending on whether the device is of fermionic or bosonic nature. Using scattering theory, we show that the precision is bounded by constraints set by the entropy production and by the activity in the spirit of thermodynamic or kinetic uncertainty relations, valid for fermionic and bosonic quantum systems also in the absence of time-reversal symmetry. Furthermore, we derive a combined thermodynamic kinetic uncertainty relation, which is tight over a wide range of parameters and can hence predict the reachable precision of a device. Since these constraints can be expressed in terms of observables accessible in transport measurements, such as currents and bandwidth, we foresee that the tight thermodynamic kinetic uncertainty-like bounds are also useful as an inference tool: they can be exploited to estimate entropy production from transport observables, such as the charge current and its noise, which are more easily accessible in experiment.
We review random matrix approaches to chaotic wave scattering and transport in open systems. Starting from the effective non-Hermitian Hamiltonian formulation, we discuss the scattering matrix, reaction matrix, time delays, and complex resonances as complementary probes of open chaotic dynamics. We emphasize universal statistics governed by symmetry, openness, and channel coupling. Topics include the maximum-entropy description of fixed-energy scattering and its applications to quantum transport, energy correlations, resonance and eigenfunction statistics, and selected wave-chaotic phenomena induced by finite absorption. The focus throughout is on non-perturbative methods and universal structures underlying open quantum and wave chaotic systems.
In this work we study quantum transport phenomena in two different types of systems. The first type corresponds to so-called complex quantum systems, such as chaotic ballistic cavities and disordered quantum wires, which have a complex distribution of energy levels and transmission eigenvalues. This class of system does not admit a simple description in terms of a fixed Hamiltonian, and therefore we will make a statistical approach of its transport properties through Random Matrices Theory. We obtain exact expressions for the first three moments of the heat conductance of a quantum chain that crosses over from a superconducting quantum dot to a superconducting disordered quantum wire. Our analytic solution provides exact detailed descriptions of some smooth transitions that can be observed in the system as a function of its length, which include ballistic-metallic and metallic-insulating transitions. The two Bogolyubov de Gennes symmetry classes with time-reversal symmetry are accounted for. The striking effect of total suppression of the insulating regime in systems with broken spin-rotation invariance is observed at large length scales. For a single channel system, this anomalous effect can be interpreted as a signature of the presence of the elusive Majorana fermion in a condensed matter system. The second type of system corresponds to qubits, which, unlike complex systems, can be described by very simple Hamiltonians. In this case, we study the properties of open systems using master equations. We present a study of non-equilibrium thermodynamics of qubit systems submitted to quantum control. More specifically, we performed a comparative study of two types of simple two-level non-interacting quantum transport systems coupled to two bosonic and fermionic reservoirs respectively. Each system is submitted to a Wiseman-Milburn type feedback scheme in the formulation of stochastic thermodynamics. We see the effects of finite temperature and time delay on two specific feedback applications: a heat pump and a purification protocol. We observed a clear signature of the purity of the qubits in the Full Counting Statistics observed in the current flowing through the system.