Two-body correlations in quantum many-body systems: A confrontation between different techniques

J. L. Ballot, M. Fabre de la Ripelle, Jesús Navarro

Jan Chwedeńczuk

Since John Bell formulated his paramount inequality for a pair of spin-1/2 particles, quantum mechanics has been confronted with the postulates of local realism with various equivalent configurations. Current technology, with its advanced manipulation and detection methods, allows to extend the Bell tests to more complex structures. The aim of this work is to analyze a set of Bell inequalities suitable for a possibly broad family of many-body systems with the focus on bosonic qubits. We develop a method that allows for a step-by-step study of the many-body Bell correlations, for instance among atoms forming a two-mode Bose-Einstein condensate or between photons obtained from the parametric-down conversion. The presented approach is valid both for cases of fixed and non-fixed number of particles, hence it allows for a thorough analysis of quantum correlations in a variety of many-body systems.

Jan Chwedeńczuk

Since John Bell formulated his paramount inequality for a pair of spin-1/2 particles, quantum mechanics has been confronted with the postulates of local realism with various equivalent configurations. Current technology, with its advanced manipulation and detection methods, allows to extend the Bell tests to more complex structures. The aim of this work is to analyze a set of Bell inequalities suitable for a possibly broad family of many-body systems with the focus on bosonic qubits. We develop a method that allows for a step-by-step study of the many-body Bell correlations, for instance among atoms forming a two-mode Bose-Einstein condensate or between photons obtained from the parametric-down conversion. The presented approach is valid both for cases of fixed and non-fixed number of particles, hence it allows for a thorough analysis of quantum correlations in a variety of many-body systems.

義夫 倉本

Hossein Hosseinabadi, Darrick E. Chang, Jamir Marino

Light-matter interfaces have now entered a new stage marked by the ability to engineer quantum correlated states under driven-dissipative conditions. To propel this new generation of experiments, we are confronted with the need to model nonunitary many-body dynamics in strongly coupled regimes by transcending traditional approaches in quantum optics. In this work, we contribute to this program by adapting a functional-integral technique, conventionally employed in high-energy physics, in order to obtain nonequilibrium dynamics for interacting light-matter systems. Our approach is grounded in constructing “two-particle irreducible” (2PI) effective actions, which provide a nonperturbative and conserving framework for describing quantum evolution at a polynomial cost in time. We apply our method to complement the analysis of spin-glass formation in the context of frustrated multimode cavity quantum electrodynamics, initiated in our accompanying work [Hosseinabadi , ]. Finally, we outline the capability of the technique to describe other near-term platforms in many-body quantum optics, and its potential to make predictions for this new class of experiments. Published by the American Physical Society 2024

Yoshio Kuramoto