Abstract
We use the quantum Fisher information (QFI) to diagnose a dynamical phase transition (DPT) in a closed quantum system, which is usually defined in terms of non-analytic behaviour of a time-averaged order parameter. Employing the Lipkin-Meshkov-Glick model as an illustrative example, we find that the DPT correlates with a peak in the QFI that can be explained by a generic connection to an underlying excited-state quantum phase transition that also enables us to also relate the scaling of the QFI with the behaviour of the order parameter. Motivated by the QFI as a quantifier of metrologically useful correlations and entanglement, we also present a robust interferometric protocol that can enable DPTs as a platform for quantum-enhanced sensing.
Highlights
The isolation and control of quantum systems at the singleparticle level in atomic, molecular, and optical platforms has driven a surge of experimental interest in studying nonequilibrium phenomena
We theoretically demonstrate that the quantum Fisher information (QFI) [31], which quantifies metrologically useful entanglement and correlations in a quantum state [32,33,34], can be used to characterize dynamical phase transition (DPT) via an underlying connection to excited-state quantum phase transition (EQPTs) [12,28]
We have theoretically demonstrated that the QFI can be used to diagnose DPTs
Summary
The isolation and control of quantum systems at the singleparticle level in atomic, molecular, and optical platforms has driven a surge of experimental interest in studying nonequilibrium phenomena. Analogous to equilibrium phase transitions, DPTs are characterized by a time-averaged order parameter that distinguishes dynamical phases and features nonanalytic behavior at the critical point. An important current question is to understand the role of entanglement and coherence in DPTs [8,28,29,30] and how these might be harnessed for quantum science applications In this manuscript, we theoretically demonstrate that the quantum Fisher information (QFI) [31], which quantifies metrologically useful entanglement and correlations in a quantum state [32,33,34], can be used to characterize DPTs via an underlying connection to excited-state quantum phase transition (EQPTs) [12,28]. This latter result, in particular, opens a realistic path for the harnessing of DPTs for quantum-enhanced sensing [38]
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