High-Fidelity Transmon Reset with a Multimode Acoustic Resonator

TL;DR

This paper demonstrates a novel qubit reset method using a cold phononic bath via a high-overtone bulk acoustic resonator, significantly reducing residual excited-state populations in superconducting circuits.

Contribution

It introduces a new approach employing a phononic bath for qubit reset, achieving lower residual populations than existing methods.

Findings

Residual excited-state population below 10^-4

Improvement of one to two orders of magnitude over existing schemes

Effective cooling of qubits using a phononic bath

Abstract

Achieving sufficiently low residual excited-state populations remains a key challenge in superconducting quantum circuits, particularly for protocols operating close to noise limits or requiring repeated qubit initialization. Existing protocols primarily address this challenge through sophisticated control, engineered dissipation, or feedback mechanisms. Here, we demonstrate an alternative approach in which a superconducting qubit is reset using a physically distinct, intrinsically colder phononic bath. Specifically, we interface a transmon with a high-overtone bulk acoustic resonator (HBAR), enabling cooling of the qubit into GHz-frequency modes. Using this approach, we achieve a residual excited-state population of the qubit below $10^{-4}$, representing an improvement of one to two orders of magnitude compared to existing reset schemes. These results highlight the potential of phononic baths as a resource for high-fidelity qubit initialization in superconducting circuits.