Phase-modulated decoupling and error suppression in qubit-oscillator systems

TL;DR

This paper introduces a phase-modulated scheme using discrete phase shifts to effectively decouple qubits from oscillator modes, reducing infidelity in entangling gates across various quantum systems.

Contribution

The proposed method simplifies multiqubit gate implementation by using phase modulation to suppress residual entanglement and field fluctuations, applicable to superconducting qubits and trapped ions.

Findings

Reduces residual qubit-oscillator entanglement

Suppresses effects of driving field fluctuations

Simplifies multiqubit gate protocols

Abstract

We present a scheme designed to suppress the dominant source of infidelity in entangling gates between quantum systems coupled through intermediate bosonic oscillator modes. Such systems are particularly susceptible to residual qubit-oscillator entanglement at the conclusion of a gate period which reduces the fidelity of the target entangling operation. We demonstrate how the exclusive use of discrete phase shifts in the field moderating the qubit-oscillator interaction - easily implemented with modern synthesizers - is sufficient to both ensure multiple oscillator modes are decoupled and to suppress the effects of fluctuations in the driving field. This approach is amenable to a wide variety of technical implementations including geometric phase gates in superconducting qubits and the Molmer-Sorensen gate for trapped ions. We present detailed example protocols tailored to trapped-ion experiments and demonstrate that our approach allows multiqubit gate implementation with a significant reduction in technical complexity relative to previously demonstrated protocols.