Gate-based single-shot readout of spins in silicon

TL;DR

This paper demonstrates a single-shot spin readout method in silicon quantum dots using gate-based radio-frequency reflectometry, offering a scalable alternative to charge sensors for quantum computing.

Contribution

It introduces a gate-based sensing technique for single-shot spin readout in silicon quantum dots, reducing complexity and paving the way for large-scale quantum processors.

Findings

Achieved single-shot spin readout with 73% fidelity.

Demonstrated detection of single electron tunnelling in a double quantum dot.

Showed potential for scalable qubit readout in quantum processors.

Abstract

Electron spins in silicon quantum dots provide a promising route towards realising the large number of coupled qubits required for a useful quantum processor. At present, the requisite single-shot spin qubit measurements are performed using on-chip charge sensors, capacitively coupled to the quantum dots. However, as the number of qubits is increased, this approach becomes impractical due to the footprint and complexity of the charge sensors, combined with the required proximity to the quantum dots. Alternatively, the spin state can be measured directly by detecting the complex impedance of spin-dependent electron tunnelling between quantum dots. This can be achieved using radio-frequency reflectometry on a single gate electrode defining the quantum dot itself, significantly reducing gate count and architectural complexity, but thus far it has not been possible to achieve single-shot spin readout using this technique. Here, we detect single electron tunnelling in a double quantum dot and demonstrate that gate-based sensing can be used to read out the electron spin state in a single shot, with an average readout fidelity of 73%. The result demonstrates a key step towards the readout of many spin qubits in parallel, using a compact gate design that will be needed for a large-scale semiconductor quantum processor.