Feedback control of a solid-state qubit using high-fidelity projective measurement

TL;DR

This paper demonstrates a feedback control method for superconducting qubits that achieves fast, deterministic reset and cooling, essential for quantum error correction and teleportation.

Contribution

It introduces a high-fidelity projective measurement-based feedback protocol for solid-state qubits, improving reset speed and reducing spurious excitations.

Findings

Qubit reset error of 2.4%

Reduced transmon excitation from 16% to 3%

Enables measurement-based quantum protocols

Abstract

We demonstrate feedback control of a superconducting transmon qubit using discrete, projective measurement and conditional coherent driving. Feedback realizes a fast and deterministic qubit reset to a target state with 2.4% error averaged over input superposition states, and cooling of the transmon from 16% spurious excitation to 3%. This closed-loop qubit control is necessary for measurement-based protocols such as quantum error correction and teleportation.