A singlet-triplet hole spin qubit in planar Ge

Area of Science:

• Quantum Computing
• Solid-State Physics
• Materials Science

Background:

• Spin qubits are leading candidates for quantum processors.
• Group IV hole spin qubits offer operational ease and silicon compatibility.
• Germanium (Ge) enables monolithic superconductor-semiconductor integration.

Purpose of the Study:

• Demonstrate a hole spin qubit operating below 10 mT, the critical field for aluminum.
• Exploit large out-of-plane hole g-factors in planar Ge.
• Encode the qubit into singlet-triplet states of a double quantum dot.

Main Methods:

• Utilized planar Ge double quantum dots.
• Operated qubits at magnetic fields below 10 mT.
• Employed electrically controlled g-factor difference-driven and exchange-driven rotations.

Main Results:

• Achieved tunable rotation frequencies exceeding 100 MHz.
• Observed dephasing times of 1 μs, extended to over 150 μs with echo techniques.
• Demonstrated Ge hole singlet-triplet qubits competitive with GaAs and Si qubits.

Conclusions:

• Ge hole singlet-triplet qubits show potential for on-chip integration with superconducting circuits.
• Their performance is comparable to Ge single spin qubits but with lower field operation.
• These qubits are a promising platform for scalable quantum computing architectures.