Photon and phonon statistics in a qubit-plasmon-phonon ultrastrong coupling system

TL;DR

This paper investigates photon and phonon statistics in a qubit-plasmon-phonon system under ultrastrong coupling, revealing how parity effects influence antibunching, bunching, and cross-correlations, with implications for quantum control.

Contribution

It introduces an analytic approach to analyze photon and phonon statistics in a hybrid system, highlighting the impact of parity conservation and breaking on statistical behaviors.

Findings

Both photons and phonons exhibit strong antibunching at the same frequency.

Parity breaking causes correlation functions to shift towards the central frequency, reversing statistical behaviors.

Delayed correlation functions show oscillations indicating multiple simultaneous excitations.

Abstract

We study photon/phonon statistics of a qubit-plasmon-phonon hybrid system in the ultrastrong coupling regime. The introduced qubit coupling causes parity conserving and non-conserving situations. We employ an analytic approximation approach for the parity conserving case to reveal the statistical behaviors of photons and phonons. It indicates that both photons and phonons show strong antibunching at the same frequency. Even though the bunching properties of photons/phonons occupy the dominant regions of the considered frequencies, phonons tend to weakly antibunching within the photonic strong-bunching area. In contrast, one can find that the configurations of correlation functions for both photons and phonons in the parity conserving case are squeezed towards the central frequency by parity breaking, which directly triggers the reverse statistical behaviors for the different parties at the low-frequency regions and the strong bunching properties at other frequency regions. The photon-phonon cross-correlation function also demonstrates similar parity-induced differences, indicating that the non-conserving parity induces the photon-phonon bunching behavior. We finally analyze the delayed second-order correlation function with different driving frequencies, which illustrates striking oscillations revealing the occurrence of simultaneous multiple excitations.