Time-reversal symmetry breaking in circuit-QED based photon lattices

TL;DR

This paper demonstrates how to break time-reversal symmetry in circuit-QED photon lattices using superconducting circuits, enabling the realization of chiral states and tunable band structures for advanced quantum applications.

Contribution

It introduces a method to break time-reversal symmetry in circuit-QED systems with simple superconducting circuits, supported by numerical simulations and potential applications.

Findings

Superconducting circuits can induce time-reversal symmetry breaking in photon lattices.

Constant magnetic and electric fields suffice for symmetry breaking in this setup.

Applications include chiral state transfer, on-chip circulators, and tunable Kagome lattice band structures.

Abstract

Breaking time-reversal symmetry is a prerequisite for accessing certain interesting many-body states such as fractional quantum Hall states. For polaritons, charge neutrality prevents magnetic fields from providing a direct symmetry breaking mechanism and similar to the situation in ultracold atomic gases, an effective magnetic field has to be synthesized. We show that in the circuit QED architecture, this can be achieved by inserting simple superconducting circuits into the resonator junctions. In the presence of such coupling elements, constant parallel magnetic and electric fields suffice to break time-reversal symmetry. We support these theoretical predictions with numerical simulations for realistic sample parameters, specify general conditions under which time-reversal is broken, and discuss the application to chiral Fock state transfer, an on-chip circulator, and tunable band structure for the Kagome lattice.