Rapid gate-based read-out 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 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 combination with a spin-to-charge conversion scheme, electron spin states. While these are the most sensitive detectors to date, they come with additional resources 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, read-out can be performed utilizing gates that are already in place for defining quantum dots by connecting those gates to a resonant circuit. This promising method of gate-based sensing has been developed for quantum dots with off-chip resonators, and only very recently achieved the sensitivity necessary for single-shot read-out of spins in silicon [1]. In this talk, I will describe the use of an on-chip superconducting microwave resonator to improve the sensitivity, aided by its high quality factor and impedance. Using Pauli Spin Blockade as the spin-to-charge conversion scheme, we demonstrate the gate-based read-out of a two-electron spin state in a single shot with an average fidelity of 98% in only 6 microseconds [2]. Furthermore, our latest work towards long-distance spin-spin coupling will be presented.
[1] Hu, Nat. Nano. 14, 735 (2019), and references therein.
[2] Zheng et al, Nat. Nano. 14, 742 (2019)