Single-spin qubits in isotopically enriched silicon at low magnetic field

Area of Science:

• Quantum Computing
• Solid-State Physics
• Materials Science

Background:

• Single-electron spin qubits typically require high magnetic fields (>1 Tesla) for readout via spin-dependent tunneling.
• This necessitates complex microwave engineering, hindering scalability for multi-qubit systems.
• Singlet-triplet (ST) readout offers high-fidelity spin-state measurements at lower magnetic fields without reservoirs.

Purpose of the Study:

• To demonstrate low-field operation of metal-oxide-silicon quantum dot qubits.
• To combine coherent single-spin control with ST readout for high-fidelity measurements.
• To investigate coherence limitations at low magnetic fields.

Main Methods:

• Utilized metal-oxide-silicon quantum dot qubits.
• Implemented coherent single-spin control techniques.
• Employed high-fidelity, single-shot, Pauli-spin-blockade-based ST readout at low magnetic fields (150 mT).

Main Results:

• Achieved low-field operation of silicon quantum dot qubits.
• Observed faster decoherence at low magnetic fields (T2* ~ 1-2 μs).
• Identified residual 29Si nuclear spin flips in 28Si as the primary decoherence mechanism at lower fields.

Conclusions:

• Low-field operation is feasible but faces decoherence challenges.
• Coherence times are limited by nuclear spin flips, which are more frequent at lower magnetic fields.
• Isotopic enrichment of silicon substrates is crucial for scalable silicon quantum processors.