Parametric phase modulation in superconducting circuits

TL;DR

This paper introduces a phase-modulation technique for superconducting qubits that allows precise control of coupling strength without altering qubit parameters, enhancing quantum simulation and gate operations.

Contribution

It presents a novel phase-modulation scheme to tune interaction strength between coupled qubits, expanding control options in superconducting quantum circuits.

Findings

Achieved broad range of coupling strengths via phase control

Validated modulation effectiveness through population dynamics and spectroscopy

Demonstrated operation at both sweet and off-sweet spots

Abstract

Parametric modulation, valued for its versatility, is widely employed in superconducting circuits for quantum simulations and high-fidelity two-qubit gates. Conventionally, the qubit coupling strength is determined by the amplitude of the parametric flux pulse, which affects the qubit parameters dramatically. In this paper, we propose and implement a phase-modulation scheme to tune the interaction strength via adjustment of the relative phase between the parametric flux pulses applied to two coupled qubits. We characterize this modulation for sideband couplings, at both sweet and off-sweet spots, achieving a broad range of coupling strengths, as confirmed by both population dynamics and spectroscopy methods. This approach enables phase-controlled modulation of coupling strength, providing a promising candidate for parametrically driven quantum simulations and gate operations.