Majorana path integral for nonequilibrium dynamics of two-level systems

拓扑超导体中的耗散诱导稳态：机制与设计原则

Dissipation-Induced Steady States in Topological Superconductors: Mechanisms and Design Principles

研究拓扑超导体中非平衡退相干稳态的条件，通过环境耗散场影响下存在不成对马约拉纳模式的拓扑超导体，建立平衡马约拉纳零模与非平衡动能零模之间的对应关系，并提出通过控制耗散工程稳定退相干稳态的方法。

Transfer-matrix summation of path integrals for transport through nanostructures

On the basis of the method of iterative summation of path integrals (ISPI), we develop a numerically exact transfer-matrix method to describe the nonequilibrium properties of interacting quantum-dot systems. For this, we map the ISPI scheme to a transfer-matrix approach, which is more accessible to physical interpretation, allows for a more transparent formulation of the theory, and substantially improves the efficiency. In particular, the stationary limit is directly implemented, without the need of extrapolation. The resulting new method, referred to as "transfer-matrix summation of path int…

A baby Majorana quantum formalism

The aim of the present paper is to introduce and to discuss the most basic fundamental concepts of quantum physics by means of a simple and pedagogical example. An appreciable part of its content presents original results. We start with the Euclidean plane which is certainly a paradigmatic example of a Hilbert space. The pure states form the unit circle (actually a half of it), the mixed states form the unit disk (actually a half of it), and rotations in the plane rule time evolution through Majorana-like equations involving only real quantities for closed and open systems. The set of pure sta…

从非平衡自旋-玻色系统出发，通过Keldysh泛函积分推导一个$\PT$对称的非厄米特正弦-戈登模型

Derivation of a $\PT$-Symmetric Sine-Gordon Model from a Nonequilibrium Spin-Boson System via Keldysh Functional Integrals

本文通过Keldysh泛函积分、Lang-Firsov极化子变换、玻色化和格森 coherent-state 自旋迹，推导出非平衡自旋-玻色系统到$\PT$对称非厄米特正弦-戈登有效理论的微观推导，并给出了自旋-玻色微观参数与非厄米特正弦-戈顿耦合之间的显式字典。

Majorana 和 Dirac 费米子的 Brownian SYK 模型的 Frame potential

Frame potential of Brownian SYK model of Majorana and Dirac fermions

本文通过 Keldysh 路径积分研究 Brownian SYK 模型的 Frame potential，发现 $q>2$ 时晚期鞍点正确饱和至 Haar 值，$q=2$ 时仅在 Gaussian 态空间饱和，并解决了 Dirac 费米子的全局 $U(1)$ 对称性问题。

Experimental Validation of Fully Quantum Fluctuation Theorems Using Dynamic Bayesian Networks

Fluctuation theorems are fundamental extensions of the second law of thermodynamics for small systems. Their general validity arbitrarily far from equilibrium makes them invaluable in nonequilibrium physics. So far, experimental studies of quantum fluctuation relations do not account for quantum correlations and quantum coherence, two essential quantum properties. We here experimentally verify detailed and integral fully quantum fluctuation theorems for heat exchange using two quantum-correlated thermal spins-1/2 in a nuclear magnetic resonance setup. We confirm, in particular, individual inte…

量子退火中的绝热瓶颈与顺磁振子的非平衡动力学

Adiabatic Bottlenecks in Quantum Annealing and Nonequilibrium Dynamics of Paramagnons

本文利用非平衡格林函数方法分析量子退火路径上的统计涨落与集体激发，并以量子 Sherrington-Kirkpatrick 自旋玻璃为例，揭示了实例特定的绝热瓶颈。

具有非保守漂移的扩散过程的（非平衡）动力学

(Nonequilibrium) dynamics of diffusion processes with non-conservative drifts

本文研究了具有非保守漂移的扩散过程动力学，通过 $N=3$ 磁线索探讨了非保守漂移扩散、带电粒子布朗运动与欧几里得量子力学间的关联，并分析了欧几里得映射在概率描述中的局限性。

Introduction to Nonequilibrium Quantum Field Theory

There has been substantial progress in recent years in the quantitative understanding of the nonequilibrium time evolution of quantum fields. Important topical applications, in particular in high energy particle physics and cosmology, involve dynamics of quantum fields far away from the ground state or thermal equilibrium. In these cases, standard approaches based on small deviations from equilibrium, or on a sufficient homogeneity in time underlying kinetic descriptions, are not applicable. A particular challenge is to connect the far-from-equilibrium dynamics at early times with the approach…

Schwinger's Quantum Action Principle: From Dirac's formulation through Feynman's path integrals, the Schwinger-Keldysh method, quantum field theory, to source theory

Starting from the earlier notions of stationary action principles, we show how Julian Schwinger's Quantum Action Principle descended from Dirac's formulation, which independently led Feynman to his path-integral formulation of quantum mechanics. The connection between the two is brought out, and applications are discussed. The Keldysh-Schwinger time-cycle method of extracting matrix elements in nonequilibrium situations is described. The variational formulation of quantum field theory and the development of source theory constitute the latter part of this work. In this document, derived from S…