Dynamical Phase Transitions in Open Quantum Walks

• URL: http://arxiv.org/abs/2508.11947v1
• Date: Sat, 16 Aug 2025 07:17:36 GMT
• Title: Dynamical Phase Transitions in Open Quantum Walks
• Authors: Stefano Longhi,
• Abstract summary: We show a novel class of critical behavior in open quantum systems, where decoherence-induced classicalization enables access to non-Hermitian spectral phenomena.<n>Our results offer promising implications for quantum technologies, including quantum simulation, error mitigation, and the engineering of controllable non-equilibrium quantum states.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Dynamical phase transitions in the relaxation behavior of stochastic quantum walks are investigated, focusing on systems where coherent unitary evolution is periodically interrupted by dephasing. This interplay leads to a classicalization of the dynamics, effectively described by non-equilibrium Markovian processes that can violate detailed balance. As a result, such systems exhibit a richer and more complex spectral structure than their equilibrium counterparts. Extending recent insights from classical Markov dynamics [G. Teza {\it et al.}, Phys. Rev. Lett. {\bf 130}, 207103 (2023)], we demonstrate that these quantum-classical hybrid systems can host not only first-order dynamical phase transitions -- characterized by eigenvalue crossings -- but also second-order transitions marked by the coalescence of eigenvalues and eigenvectors at exceptional points. We analyze two paradigmatic models: a quantum walk on a ring under gauge fields and a walk on a finite line with internal degrees of freedom, both exhibiting distinct mechanisms for breaking detailed balance. These findings reveal a novel class of critical behavior in open quantum systems, where decoherence-induced classicalization enables access to non-Hermitian spectral phenomena. Beyond their fundamental interest, our results offer promising implications for quantum technologies, including quantum simulation, error mitigation, and the engineering of controllable non-equilibrium quantum states.

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