Gate-based single-shot readout of spins in silicon

West, Anderson and Hensen, Bas and Jouan, Alexis and Tanttu, Tuomo and Yang, Chih-Hwan and Rossi, Alessandro and Gonzalez-Zalba, M. Fernando and Hudson, Fay and Morello, Andrea and Reilly, David J. and Dzurak, Andrew S. (2019) Gate-based single-shot readout of spins in silicon. Nature Nanotechnology, 14 (5). pp. 437-443. ISSN 1748-3387

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    Abstract

    Electron spins in silicon quantum dots provide a promising route towards realizing the large number of coupled qubits required for a useful quantum processor 1–7 . For the implementation of quantum algorithms and error detection 8–10 , qubit measurements are ideally performed in a single shot, which is presently achieved using on-chip charge sensors, capacitively coupled to the quantum dots 11 . 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 12 . Alternatively, the spin state can be measured directly by detecting the complex impedance of spin-dependent electron tunnelling between quantum dots 13–15 . This can be achieved using radiofrequency reflectometry on a single gate electrode defining the quantum dot itself 15–19 , significantly reducing the 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.