Silicon spin qubits are one of the leading platforms for quantum computation1,2. As with any qubit implementation, a crucial requirement is the ability to measure individual quantum states rapidly and with high fidelity. Since the signal from a single electron spin is minute, the different spin states are converted to different charge states3,4. Charge detection, so far, has mostly relied on external electrometers5,6,7, which hinders scaling to two-dimensional spin qubit arrays2,8,9. Alternatively, gate-based dispersive read-out based on off-chip lumped element resonators has been demonstrated10,11,12,13, but integration times of 0.2–2 ms were required to achieve single-shot read-out14,15,16. Here, we connect an on-chip superconducting resonant circuit to two of the gates that confine electrons in a double quantum dot. Measurement of the power transmitted through a feedline coupled to the resonator probes the charge susceptibility, distinguishing whether or not an electron can oscillate between the dots in response to the probe power. With this approach, we achieve a signal-to-noise ratio of about six within an integration time of only 1 μs. Using Pauli’s exclusion principle for spin-to-charge conversion, we demonstrate single-shot read-out of a two-electron spin state with an average fidelity of >98% in 6 μs. This result may form the basis of frequency-multiplexed read-out in dense spin qubit systems without external electrometers, therefore simplifying the system architecture.
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The data reported in this paper are archived at https://doi.org/10.4121/uuid:8df1a6fa-9230-400f-a790-1b7714b1aad5.
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The authors thank T.F. Watson, J.P. Dehollain, P. Harvey-Collard, U.C. Mendes, B. Hensen and other members of the spin qubit team at QuTech for useful discussions, L.P. Kouwenhoven and his team for access to NbTiN films, and P. Eendebak and L. Blom for software support. This research was undertaken thanks in part to funding from the European Research Council (ERC Synergy Quantum Computer Lab), the Netherlands Organisation for Scientific Research (NWO/OCW) as part of the Frontiers of Nanoscience (NanoFront) programme and Intel Corporation.
The authors declare no competing interests.
Peer review information: Nature Nanotechnology thanks Hongwen Jiang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Figs. 1–2