Macroscopic quantum self-trapping in bosonic Josephson junctions: An exact quantum treatment

Year: 2026

Authors: Bardin A., Minguzzi A., Salasnich L.

Autors Affiliation: Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Via Marzolo 8, I-35131 Padua, Italy; Ist Nazl Fis Nucleare, Sez Padova, Via Marzolo 8, I-35131 Padua, Italy; Univ Grenoble Alpes, CNRS, LPMMC, F-38000 Grenoble, France; CNR, Ist Nazl Ott, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy.

Abstract: We investigate the fully quantum evolution of the population imbalance in a perfectly symmetric BoseJosephson junction modeled by a two-mode Bose-Hubbard Hamiltonian, focusing on the validity of macroscopic quantum self-trapping beyond the mean-field theory. We show that for any finite number of particles, the exact quantum dynamics leads to the breakdown of macroscopic quantum self-trapping after a finite time, regardless of the initial state. Using the symmetries of the Bose-Hubbard Hamiltonian, we provide a mathematical demonstration of this result and analyze the spectral properties governing the dynamics. We identify a branching behavior in the eigenvalue differences and a nontrivial structure of the population-imbalance amplitudes. These features allow us to distinguish two clearly different dynamical regimes and to elucidate the mechanism leading to the emergence of a quasi-macroscopic quantum self-trapping regime for large particle numbers. These findings bridge the gap between mean-field predictions and exact quantum dynamics and provide insight into the emergence of classical nonlinear behavior from finite quantum many-body systems.

Journal/Review: PHYSICAL REVIEW A

Volume: 113 (3)      Pages from: L031305-1  to: L031305-5

More Information: This work was partially supported by the IniziativaSpecifica Quantum of INFN, by the European Union-NextGenerationEU within the National Center for HPC, Big Data and Quantum Computing (Project No. CN00000013, CN1 Spoke 10: Quantum Computing), by the EU Project PASQuanS 2 Programmable Atomic Large-Scale Quantum Simulation, and the National Grant of the Italian Ministry of University and Research for the PRIN project Quantum Atomic Mixtures: Droplets, Topological Structures, and Vortices.
KeyWords: Bose-einstein Condensation; Coherent States
DOI: 10.1103/mzg8-gz84