Superconducting spin qubit
To date, the most promising solid-state approaches to the development of quantum information processing systems are based on the circulating supercurrents of superconducting circuits and the manipulation of the spin properties of electrons in semiconductor quantum dots. Hays et al. combined the desirable aspects of both approaches, the scalability of the superconducting circuits and the compact footprint of the quantum dots to design and manufacture a superconducting spin qubit (see the perspective of Wendin and Shumeiko). This so-called Andreev spin qubit offers the opportunity to develop a new platform for quantum information processing.
science, abf0345, this edition p. 430; see also abk0929, p. 390
Two promising architectures for solid-state quantum information processing are based on electron spins electrostatically trapped in semiconductor quantum dots and the collective electrodynamic modes of superconducting circuits. Superconducting electrodynamic qubits contain macroscopic electron counts and offer the advantage of greater coupling, while semiconductor spin qubits contain single electrons that are trapped in microscopic volumes but more difficult to link. We combined beneficial aspects of both platforms in the Andreev spin qubit: the spin degree of freedom of an electronic quasiparticle trapped in the supercurrent-carrying Andreev levels of a Josephson semiconductor nanowire. We performed coherent spin manipulation by combining single-shot circuit quantum electrodynamics readout and spin-flip Raman transitions and found a spin-flip time TS. = 17 microseconds and a spin coherence time T2E = 52 nanoseconds. These results herald a regime of supercurrent-mediated coherent spin-photon coupling on the single quantum level.