Radio-frequency detected fast charge sensing in undoped silicon quantum dots

TL;DR

This paper demonstrates a radio-frequency reflectometry technique for fast, sensitive charge sensing in undoped silicon quantum dots, achieving the shortest single-shot readout time in silicon and guiding device design for high-fidelity qubit measurement.

Contribution

It introduces a novel gate geometry that reduces parasitic capacitance, enabling rapid and sensitive charge detection in silicon quantum dots for quantum computing applications.

Findings

Achieved single-shot readout in 0.8 μs, the fastest in silicon.

Reduced parasitic capacitance improves measurement speed and sensitivity.

Demonstrated distinction between charge states under Pauli spin blockade.

Abstract

Spin qubits in silicon quantum dots offer a promising platform for a quantum computer as they have a long coherence time and scalability. The charge sensing technique plays an essential role in reading out the spin qubit as well as tuning the device parameters and therefore its performance in terms of measurement bandwidth and sensitivity is an important factor in spin qubit experiments. Here we demonstrate fast and sensitive charge sensing by a radio-frequency reflectometry of an undoped, accumulation-mode Si/SiGe double quantum dot. We show that the large parasitic capacitance in typical accumulation-mode gate geometries impedes reflectometry measurements. We present a gate geometry that significantly reduces the parasitic capacitance and enables fast single-shot readout. The technique allows us to distinguish between the singly- and doubly-occupied two-electron states under the Pauli spin blockade condition in an integration time of 0.8 {\mu}s, the shortest value ever reported in silicon, by the signal-to-noise ratio of 6. These results provide a guideline for designing silicon spin qubit devices suitable for the fast and high-fidelity readout.