Equilibrium and Transport Properties of Quantum Many-Body Systems

Youqi Ke, Sheng Meng, Ke Xia +1 more

Under external driving forces, the system deviates from the equilibrium distribution and enters a non-equilibrium state, resulting in transport phenomena of both charge and energy and the emergence of many novel non-equilibrium phases. The transport of charge and energy through a quantum many-body material system is a fundamental process in the conversion and storage of energy and information, and material properties can undergo significant changes at the far-from-equilibrium conditions. A deep understanding and accurate calculation of non-equilibrium states in materials and devices, including transport properties, are essential for enhancing the control of material properties and advancing the related manufacturing technologies, constituting a key aspect of condensed matter physics and computational physics.

Simone Montangero

Klée Pollock

Pengfei Zhang, Yu Gao, Xiansong Xu +29 more

Non-equilibrium quantum transport is crucial to technological advances ranging from nanoelectronics to thermal management. In essence, it deals with the coherent transfer of energy and (quasi-)particles through quantum channels between thermodynamic baths. A complete understanding of quantum transport thus requires the ability to simulate and probe macroscopic and microscopic physics on equal footing. Using a superconducting quantum processor, we demonstrate the emergence of non-equilibrium steady quantum transport by emulating the baths with qubit ladders and realising steady particle currents between the baths. We experimentally show that the currents are independent of the microscopic details of bath initialisation, and their temporal fluctuations decrease rapidly with the size of the baths, emulating those predicted by thermodynamic baths. The above characteristics are experimental evidence of pure-state statistical mechanics and prethermalisation in non-equilibrium many-body quantum systems. Furthermore, by utilising precise controls and measurements with single-site resolution, we demonstrate the capability to tune steady currents by manipulating the macroscopic properties of the baths, including filling and spectral properties. Our investigation paves the way for a new generation of experimental exploration of non-equilibrium quantum transport in strongly correlated quantum matter. The use of quantum simulators for studying non-equilibrium quantum transport has been limited. Here the authors demonstrate the steady quantum transport between many-body qubit baths on a superconducting quantum processor, revealing insights into pure-state statistical mechanics for nonequilibrium quantum systems.

藤 陽平

Ali Maghari, V. H. Maleki

In this paper, we present a quantum statistical mechanical formulation from our recently analytical expressions for partial-wave transition matrix of a three-particle system. We report the quantum reactive cross sections for three-body scattering processes 1+(2,3)→1+(2,3) as well as recombination 1+(2,3)→1+(3,1) between one atom and a weakly-bound dimer. The analytical expressions of three-particle transition matrices and their corresponding cross-sections were obtained from the threedimensional Faddeev equations subjected to the rank-two non-local separable potentials of the generalized Yamaguchi form. The equilibrium quantum statistical mechanical properties such partition function and equation of state as well as non-equilibrium quantum statistical properties such as transport cross-sections and their corresponding transport collision integrals were formulated analytically. This leads to obtain the transport properties, such as viscosity and diffusion coefficient of a moderate dense gas.