Coherent manipulation of an Andreev spin qubit

Area of Science:

• Quantum Information Science
• Condensed Matter Physics
• Quantum Computing Hardware

Background:

• Existing quantum computing architectures include semiconductor spin qubits and superconducting electrodynamic qubits, each with distinct advantages and limitations.
• Semiconductor spin qubits offer individual electron control but face challenges in scalability and inter-qubit coupling.
• Superconducting qubits provide strong coupling but involve macroscopic electron ensembles.

Purpose of the Study:

• To combine the strengths of semiconductor spin qubits and superconducting circuits into a novel quantum information processing architecture.
• To explore the potential of using the spin degree of freedom of quasiparticles in Josephson semiconductor nanowires for quantum applications.

Main Methods:

• Development of the Andreev spin qubit, utilizing the spin of an electronic quasiparticle trapped in Andreev levels of a Josephson semiconductor nanowire.
• Implementation of coherent spin manipulation techniques, including single-shot circuit-quantum-electrodynamics (cQED) readout.
• Utilized spin-flipping Raman transitions for qubit control and measurement.

Main Results:

• Achieved coherent spin manipulation of the Andreev spin qubit.
• Measured a spin-flip time (T_S) of 17 microseconds.
• Determined a spin coherence time (T_2E) of 52 nanoseconds.

Conclusions:

• The Andreev spin qubit successfully integrates the spin degree of freedom with supercurrents in semiconductor nanowires.
• Demonstrated the feasibility of coherent spin manipulation and readout in this hybrid system.
• These findings open a new avenue for supercurrent-mediated coherent spin-photon coupling at the single-quantum level, advancing solid-state quantum information processing.