Microwave-Induced Amplitude and Phase Tunable Qubit-Resonator Coupling in Circuit Quantum Electrodynamics

TL;DR

This paper demonstrates a method to tune the amplitude and phase of qubit-resonator coupling in circuit quantum electrodynamics using a single drive tone, enabling precise control of qubit-photon interactions.

Contribution

The authors experimentally realize a scheme for tunable qubit-resonator coupling via a single coherent drive, expanding control capabilities in superconducting quantum circuits.

Findings

Achieved coupling strengths of about 10 MHz

Coupling is tunable in both amplitude and phase

Scheme can generate microwave photons with controlled shapes

Abstract

In the circuit quantum electrodynamics architecture, both the resonance frequency and the coupling of superconducting qubits to microwave field modes can be controlled via external electric and magnetic fields to explore qubit -- photon dynamics in a wide parameter range. Here, we experimentally demonstrate and analyze a scheme for tuning the coupling between a transmon qubit and a microwave resonator using a single coherent drive tone. We treat the transmon as a three-level system with the qubit subspace defined by the ground and the second excited states. If the drive frequency matches the difference between the resonator and the qubit frequency, a Jaynes-Cummings type interaction is induced, which is tunable both in amplitude and phase. We show that coupling strengths of about 10 MHz can be achieved in our setup, limited only by the anharmonicity of the transmon qubit. This scheme has been successfully used to generate microwave photons with controlled temporal shape [Pechal et al., Phys. Rev. X 4, 041010 (2014)] and can be directly implemented with superconducting quantum devices featuring larger anharmonicity for higher coupling strengths.