Two-photon probe of the Jaynes-Cummings model and symmetry breaking in circuit QED

TL;DR

This paper demonstrates the observation of two-photon driven dynamics and symmetry breaking in a superconducting circuit QED system, providing insights into multiphoton processes and quantum symmetries.

Contribution

It reports the first experimental evidence of two-photon driven Jaynes-Cummings model signatures and symmetry breaking in circuit QED, combining experimental results with theoretical analysis.

Findings

Observation of two-photon driven level anticrossings

Evidence of symmetry breaking when parity is not well-defined

Insight into multiphoton processes in superconducting qubits

Abstract

Superconducting qubits behave as artificial two-level atoms and are used to investigate fundamental quantum phenomena. In this context, the study of multi-photon excitations occupies a central role. Moreover, coupling superconducting qubits to on-chip microwave resonators has given rise to the field of circuit QED. In contrast to quantum-optical cavity QED, circuit QED offers the tunability inherent to solid-state circuits. In this work, we report on the observation of key signatures of a two-photon driven Jaynes-Cummings model, which unveils the upconversion dynamics of a superconducting flux qubit coupled to an on-chip resonator. Our experiment and theoretical analysis show clear evidence for the coexistence of one- and two-photon driven level anticrossings of the qubit-resonator system. This results from the symmetry breaking of the system Hamiltonian, when parity becomes a not well-defined property. Our study provides deep insight into the interplay of multiphoton processes and symmetries in a qubit-resonator system.