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arXiv:2610.12647 · Advanced Quantum Technologies

Latent Symmetry in Quantum Zeno Dynamics

Stefano Longhi

quant-phSubmitted Oct 8, 2026• Announced Oct 12, 2026• 0 citations

Abstract

Quantum Zeno dynamics constrains a continuously monitored system to measurement-selected subspaces. Here we show that the structure of such Zeno subspaces can be governed by a \emph{latent symmetry}, namely a symmetry that is absent from the geometry of the underlying physical network. We consider a minimal circuit-QED network of coupled microwave resonators subject to quantum-nondemolition (QND) monitoring of local photon occupations. Two distinguished resonators are geometrically inequivalent, yet are exactly exchanged by a latent symmetry of the network. Strong monitoring partitions the single-excitation Hilbert space into three quantum-Zeno subspaces, two of which correspond to localization on the distinguished resonators. Latent symmetry exactly exchanges these two Zeno subspaces and enforces identical escape and residence statistics despite their different microscopic environments. In the strong-measurement regime their residence times grow linearly with the measurement strength and diverge in the ideal Zeno limit, where the measurement subspaces become dynamically disconnected. Our results show that latent symmetry can act as a hidden organizing principle of quantum Zeno dynamics, imposing exact relations between measurement-selected subspaces that are geometrically inequivalent in the physical system.

Comments: 12 pages, 4 figures, accepted for publication in Advanced Quantum Technologies

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We unify the quantum Zeno effect (QZE) and the ``bang-bang'' (BB) decoupling method for suppressing decoherence in open quantum systems: in both cases strong coupling to an external system or apparatus induces a dynamical superselection rule that partitions the open system's Hilbert space into quantum Zeno subspaces. Our unification makes use of von Neumann' s ergodic theorem and avoids making any of the symmetry assumptions usually made in discussions of BB. Thus we are able to generalize the BB to arbitrary fast and strong pulse sequences, requiring no symmetry, and to show the existence of two alternatives to a pulsed BB: continuous decoupling and pulsed measurements. Our unified treatment enables us to derive limits on the efficacy of the BB method: we explicitly show that the inverse QZE implies that the BB can in some cases accelerate, rather than inhibit, decoherence.