# Fast gate-based readout of silicon quantum dots using Josephson parametric amplification

## TL;DR

This paper demonstrates a significant speed and fidelity improvement in silicon quantum dot spin readout by integrating a Josephson parametric amplifier with RF gate sensing, enabling faster quantum error correction.

## Contribution

It introduces the use of a Josephson parametric amplifier in RF gate-based sensing for silicon quantum dots, achieving faster and more sensitive spin state readout.

## Key findings

- Achieved singlet-triplet single-shot readout fidelity of 99.7% in 1 μs.
- Reduced integration time by a factor of 30 compared to previous methods.
- Lower RF power operation while maintaining high SNR.

## Abstract

Spins in silicon quantum devices are promising candidates for large-scale quantum computing. Gate-based sensing of spin qubits offers compact and scalable readout with high fidelity, however further improvements in sensitivity are required to meet the fidelity thresholds and measurement timescales needed for the implementation of fast-feedback in error correction protocols. Here, we combine radio-frequency gate-based sensing at 622 MHz with a Josephson parametric amplifier (JPA), that operates in the 500-800 MHz band, to reduce the integration time required to read the state of a silicon double quantum dot formed in a nanowire transistor. Based on our achieved signal-to-noise ratio (SNR), we estimate that singlet-triplet single-shot readout with an average fidelity of 99.7% could be performed in 1 $\mu$s, well-below the requirements for fault-tolerant readout and 30 times faster than without the JPA. Additionally, the JPA allows operation at a lower RF power while maintaining identical SNR. We determine a noise temperature of 200 mK with a contribution from the JPA (25%), cryogenic amplifier (25%) and the resonator (50%), showing routes to further increase the read-out speed.