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arXiv · 2608.08267

Quantum-classical crossover in noisy monitored oscillators

Joseph M. Ryan·Simon Gorbaty·Stephen W. Teitsworth·Crystal Noel
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Abstract

The quantum first-passage problem involves stochastic trajectories conditioned on measurement outcomes. The timing statistics of such trajectories remain largely unexplored in open quantum systems. Here, we investigate the first-passage time to an energy threshold for a ubiquitous model: a harmonic oscillator driven by classical additive noise. We find that projective measurements and energy quantization lead to substantial differences between the quantum and classical first-passage-time distributions at low thresholds, while these differences gradually diminish as the threshold energy increases. We treat the problem using both ensemble-averaged conditioned density-matrix dynamics and trajectory-resolved stochastic pure-state dynamics. The two descriptions yield indistinguishable timing statistics. Quantization effects appear in the ensemble-level phase-space distributions of the surviving states and vanish at larger threshold energies. Individual trajectories reveal emergent quantum signatures from the repeated measurements, such as persistent Wigner negativity. Our results provide a framework for using first-passage processes to create measurement-induced nonclassical resource states and to study the quantum-classical crossover of monitored systems.

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Joseph M. Ryan, Simon Gorbaty, Stephen W. Teitsworth, Crystal Noel. 2026-08-08. Quantum-classical crossover in noisy monitored oscillators. https://arxiv.org/abs/2608.08267

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