Sub-microsecond high-fidelity dispersive readout of a spin qubit with squeezed photons

TL;DR

This paper demonstrates that using squeezed microwave photons in dispersive readout significantly improves the speed and fidelity of spin qubit measurements in semiconductor quantum dots, enabling sub-microsecond, high-fidelity, non-demolition readout.

Contribution

It introduces a method employing displaced squeezed vacuum states to enhance spin qubit readout fidelity and speed in semiconductor quantum dots.

Findings

Squeezed photons improve signal-to-noise ratio and fidelity.

Readout time can be reduced to sub-microsecond with >99% fidelity.

Method maintains non-demolition measurement at low microwave power.

Abstract

Fast and high-fidelity qubit measurement is essential for realizing quantum error correction, which is in turn a key ingredient to universal quantum computing. For electron spin qubits, fast readout is one of the significant road blocks toward error correction. Here we examine the dispersive readout of a single spin in a semiconductor double quantum dot coupled to a microwave resonator. We show that using displaced squeezed vacuum states for the probing photons can improve the qubit readout fidelity and speed. Under condition of proper phase matching, we find that a moderate, and only moderate, squeezing can enhance both the signal-to-noise ratio and the fidelity of the qubit-state readout, and the optimal readout time can be shortened to the sub-microsecond range with above $99\%$ fidelity. These enhancements are achieved at low probing microwave intensity, ensuring non-demolition qubit measurement.