Frequency-resolved N-photon correlations in the ultra-strong coupling regime

TL;DR

This paper explores how frequency-resolved N-photon correlations in an ultrastrongly coupled cavity QED system reveal complex spectral and statistical properties, including antibunching and bunching, influenced by symmetry-breaking effects.

Contribution

It extends frequency-resolved photon correlation analysis to the ultrastrong coupling regime, highlighting the role of parity symmetry in photon emission properties.

Findings

Revealed multiphoton antibunching and bunching effects.

Demonstrated the impact of symmetry-breaking on photon correlations.

Showed potential of correlations as a probe for light-matter interaction symmetry.

Abstract

Frequency-resolved photon emission is central to applications from quantum information encoding to high-resolution spectroscopy, and then studying their correlations is therefore essential for revealing the underlying emission pathways and multiphoton statistics. Here, we investigate frequency-resolved N-photon correlations in an ultrastrongly coupled cavity QED system where a qubit interacts with a single-mode cavity. Owing to counter-rotating interactions, the eigenstates and energy spectrum are strongly modified, giving rise to rich spectral and statistical properties in the emitted frequency-resolved photons. Through frequency-selective detection, we reveal pronounced multiphoton antibunching, as well as multiphoton bunching originating from cascade transitions among dressed eigenstates. In particular, we show that parity symmetry plays a decisive role in shaping these correlations. The symmetry-breaking opens additional transition channels and dramatically enhances the generation of correlated photon pairs and even photon triplets of different frequencies. Our work extends frequency-resolved correlations to the ultra-strong coupling regime and demonstrates their potential as a sensitive probe of symmetry in light-matter interaction systems.