Dynamical sweet spot engineering via two-tone flux modulation of superconducting qubits

TL;DR

This paper demonstrates that two-tone flux modulation creates a continuum of dynamical sweet spots in superconducting qubits, enhancing frequency control and noise resilience, which improves gate performance and scalability.

Contribution

It introduces a novel two-tone flux modulation technique to generate dynamical sweet spots, expanding qubit frequency control while maintaining coherence.

Findings

Two-tone flux modulation creates a continuum of dynamical sweet spots.

Using bichromatic flux control reduces error rates and gate times.

Flux control enables flexible qubit frequency selection with preserved coherence.

Abstract

Current superconducting quantum processors require strategies for coping with material defects and imperfect parameter targeting in order to scale up while maintaining high performance. To that end, in-situ control of qubit frequencies with magnetic flux can be used to avoid spurious resonances. However, increased dephasing due to 1/f flux noise limits performance at all of these operating points except for noise-protected sweet spots, which are sparse under DC flux bias and monochromatic flux modulation. Here we experimentally demonstrate that two-tone flux modulation can be used to create a continuum of dynamical sweet spots, greatly expanding the range of qubit frequencies achievable while first-order insensitive to slow flux noise. To illustrate some advantages of this flexibility, we use bichromatic flux control to reduce the error rates and gate times of parametric entangling operations between transmons. Independent of gate scheme, the ability to use flux control to freely select qubit frequencies while maintaining qubit coherence represents an important step forward in the robustness and scalability of near-term superconducting qubit devices.