Rapid gate-based readout of spins in silicon using an on-chip resonator

Over the past decade tremendous progress has been made on spin qubits based on electron spins in silicon gate-defined quantum dots. As with any qubit implementation, a critical requirement is the ability to read out the qubit rapidly, with high fidelity, and in a scalable manner. Much attention has been focused on improving single-electron transistors embedded in radio-frequency reflectometry circuits as charge detectors to detect, in conjunction with a spin-to-charge conversion scheme, electron spin states. While they are the most sensitive detectors to date, additional resources are required that take up valuable space near the quantum dots (gate electrodes, electron reservoirs), which makes scaling up to two-dimensional spin qubit arrays difficult. More efficiently, readout can be performed with the gates that are already in place for defining quantum dots by connecting those gates to resonant circuits. This promising method of gate-based sensing has been developed for quantum dots with off-chip resonators, and recently achieved the sensitivity necessary for single-shot readout [1]. In this talk, we describe the use of an on-chip superconducting microwave resonator instead to improve the sensitivity, aided by its high quality factor and high impedance. Using Pauli Spin Blockade as the spin-to-charge conversion scheme, we demonstrate the gate-based readout of a two-electron spin state in a single shot with an average fidelity of 98% in 6 microseconds [2]. Furthermore, on-chip resonators can potentially couple distant spin qubits. We briefly present our latest work in direction, which includes on-chip gate filters to preserve the resonator’s quality factor in the presence of quantum dot gate electrodes [3] and long-distance spin-spin interaction.

[1] Hu, Nat. Nano. 14, 735 (2019), and references therein.
[2] Zheng et al, Nat. Nano. 14, 742 (2019)
[3] Harvey-Collard et al, Phys. Rev. Applied 14, 034025 (2020)