Two Mode Photon Bunching Effect as Witness of Quantum Criticality in Circuit QED

TL;DR

This paper proposes using two-photon correlation measurements in circuit QED systems to detect quantum phase transitions by observing photon bunching effects near criticality.

Contribution

It introduces a novel scheme to identify quantum criticality through photon correlation analysis in a circuit QED setup involving an Ising chain.

Findings

Photon bunching increases near the critical point.

Quantum correlations of photonic modes signal the QPT.

The scheme is experimentally feasible in circuit QED.

Abstract

We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation, a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus, the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.