Unification of quantum Zeno-anti Zeno effects and parity-time symmetry breaking transitions


Abstract in English

The decay of any unstable quantum state can be inhibited or enhanced by carefully tailored measurements, known as the quantum Zeno effect (QZE) or anti-Zeno effect (QAZE). To date, studies of QZE (QAZE) transitions have since expanded to various system-environment coupling, in which the time evolution can be suppressed (enhanced) not only by projective measurement but also through dissipation processes. However, a general criterion, which could extend to arbitrary dissipation strength and periodicity, is still lacking. In this letter, we show a general framework to unify QZE-QAZE effects and parity-time (PT) symmetry breaking transitions, in which the dissipative Hamiltonian associated to the measurement effect is mapped onto a PT-symmetric non- Hermitian Hamiltonian, thus applying the PT symmetry transitions to distinguish QZE (QAZE) and their crossover behavior. As a concrete example, we show that, in a two-level system periodically coupled to a dissipative environment, QZE starts at an exceptional point (EP), which separates the PT-symmetric (PTS) phase and PT-symmetry broken (PTB) phase, and ends at the resonance point (RP) of the maximum PT-symmetry breaking; while QAZE extends the rest of PTB phase and remains the whole PTS phase. Such findings reveal a hidden relation between QZE-QAZE and PTS-PTB phases in non-Hermitian quantum dynamics.

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