Measuring central-spin interaction with a spin-bath by pulsed ENDOR: Towards suppression of spin diffusion...

Area of Science:

• Quantum computing
• Solid-state physics
• Materials science

Background:

• Bismuth donor spin-qubits in silicon are promising for quantum computing.
• The surrounding (29)Si impurity spin bath causes decoherence via nuclear spin diffusion at low temperatures (< 16 K).
• Understanding and mitigating this decoherence is crucial for scalable quantum technologies.

Purpose of the Study:

• To characterize the coupling between bismuth donor spin-qubits and the (29)Si spin bath.
• To investigate methods for decoupling spin-qubits from the decohering spin bath.
• To identify optimal conditions for suppressing nuclear spin diffusion.

Main Methods:

• Pulsed electron-nuclear double resonance (ENDOR) experiments were performed.
• Cluster correlation expansion simulations were utilized.
• Spin diffusion coherence times were measured and analyzed.

Main Results:

• ENDOR experiments successfully characterized the spin-bath coupling.
• Simulations predicted and experiments confirmed near-complete suppression of spin diffusion at optimal working points.
• The suppression manifested as sharply peaked divergences in spin diffusion coherence time.
• Anisotropic contributions were found to be weak, making the divergences orientation-independent.

Conclusions:

• Pulsed ENDOR is an effective technique for characterizing spin-bath interactions in silicon.
• Decoupling strategies can significantly suppress nuclear spin diffusion, a key decoherence mechanism.
• The observed sharply peaked divergences offer a distinct signature for achieving robust qubit coherence.