Spin qubits based on semiconductor quantum dots can offer high coherence times and gate fidelities, and are a potential platform for quantum computation. However, scaling up the number of qubits to the level required for fault-tolerant quantum computing is challenging and will require single-shot, low-footprint qubit readout. Here we report single-shot readout of a spin qubit unit cell using in situ dispersive readout. Our compact, foundry-fabricated unit cell is composed of two electron spins with a controllable exchange interaction, and with it we demonstrate initialization, single-shot readout and a two-electron entangling gate. From exchange oscillations, we extract a spin visibility of 80.7(8)% in the coherent control of a qubit, despite a relatively small lever arm to the resonator gate (less than 0.15(5) eV V−1). We show that the unit cell can be operated at up to 1 K with low charge noise levels, extracted using free induction decay. The state of a foundry-fabricated spin qubit unit cell, which is composed of two electron spins with a controllable exchange interaction, can be read out in a single shot using gate reflectometry.

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Nature

Researchers at CEA-Leti demonstrate single-shot in situ readout of a silicon spin qubit unit cell using gate-based dispersive reflectometry, eliminating the need for an external charge sensor. The compact, foundry-fabricated unit cell consists of two electron spins with controllable exchange interaction on a 300-mm CMOS wafer. Key results include 97% charge readout fidelity, 80.7% spin visibility, a coherence time of 423 ns (quality factor ~28), and full singlet-triplet state discrimination including the T0 state. The device operates up to 1 K with low charge noise levels two orders of magnitude below the previous device generation, making it a viable candidate for cointegration with classical cryoelectronics in scalable quantum processors.

Single-shot in situ readout of a spin qubit unit cell