Cavity quantum electrodynamics of photonic temporal crystals

TL;DR

This paper develops a quantum electrodynamical model for photonic temporal crystals, revealing quantum phenomena like phase transitions and wave-packet acceleration, and demonstrates how a single atom exhibits irreversible Rabi oscillation decay due to photonic delocalization.

Contribution

It introduces a quantum model of photonic temporal crystals, connecting classical and quantum behaviors, and uncovers novel quantum effects such as phase transitions and atom-field interaction dynamics.

Findings

Classical momentum gap linked to quantum phase transition.

Wave-packet acceleration in quantum synthetic space.

Irreversible decay of Rabi oscillations in embedded atoms.

Abstract

Photonic temporal crystals host a variety of intriguing phenomena, from wave amplification and mixing to exotic band structures, all stemming from the time-periodic modulation of optical properties. While these features have been well described classically, their quantum manifestation has remained elusive. Here, we introduce a quantum electrodynamical model of PTCs that reveals a deeper connection between classical and quantum pictures: the classical momentum gap arises from a localization-delocalization quantum phase transition in a Floquet-photonic synthetic lattice. Leveraging an effective Hamiltonian perspective, we pinpoint the critical momenta and highlight how classical exponential field growth manifests itself as wave-packet acceleration in the quantum synthetic space. Remarkably, when a two-level atom is embedded in such a cavity, its Rabi oscillations undergo irreversible decay to a half-and-half mixed state-a previously unobserved phenomenon driven by photonic delocalization within the momentum gap, even with just a single frequency mode. Our findings establish photonic temporal crystals as versatile platforms for studying nonequilibrium quantum photonics and suggest new avenues for controlling light matter interactions through time domain engineering.