Preparation of Subradiant States using Local Qubit Control in Circuit QED

TL;DR

This paper demonstrates how local phase control of individual qubit drives in circuit QED can excite dark states, suppress spontaneous emission, and enable the preparation of subradiant states for studying correlated quantum phenomena.

Contribution

It introduces a novel local control method to excite and manipulate dark states in circuit QED, advancing quantum state engineering.

Findings

Dark state excitation achieved via local phase control.

Suppression of spontaneous emission indicates subradiance.

Potential for preparing highly correlated quantum states.

Abstract

Transitions between quantum states by photon absorption or emission are intimately related to symmetries of the system which lead to selection rules and the formation of dark states. In a circuit quantum electrodynamics setup, in which two resonant superconducting qubits are coupled through an on-chip cavity and driven via the common cavity field, one single-excitation state remains dark. Here, we demonstrate that this dark state can be excited using local phase control of individual qubit drives to change the symmetry of the driving field. We observe that the dark state decay via spontaneous emission into the cavity is suppressed, a characteristic signature of subradiance. This local control technique could be used to prepare and study highly correlated quantum states of cavity-coupled qubits.