Max Hays

Department of Applied Physics, Yale University

Realization of an Andreev spin qubit

Two promising architectures for quantum information processing are electron spins trapped in semiconductor quantum dots and the collective electromagnetic modes of superconducting circuits. Here we combine these two platforms to realize the Andreev spin qubit, formed from the spin of an individual electronic quasiparticle trapped in the Andreev levels of a semiconductor nanowire Josephson element. The interplay between a spin-orbit coupling in the semiconductor and a superconducting phase bias results in a spin-split spectrum without an applied Zeeman field. We harness the resultant spin-dependent supercurrent and transition spectrum to achieve single-shot circuit QED readout of the quasiparticle spin state. Moreover, despite the forbidden direct spin transition, we demonstrate coherent spin manipulation by driving spin-flipping Raman processes in a naturally occurring -system formed by the two spin states and an excited state. We measure spin lifetimes up to T₁ = 55 μs and a tuning-parameter-independent spin coherence time T₂ = 46 ns. These results represent a new spin qubit platform with straightforward circuit QED integration and further our understanding of Andreev levels, the parent states of Majorana zero modes.