Microscopic control of $^{29}$Si nuclear spins near phosphorus donors in silicon

TL;DR

This paper demonstrates precise control of $^{29}$Si nuclear spins near phosphorus donors in silicon at very low temperatures and high magnetic fields, enabling potential qubit initialization for silicon-based quantum computers.

Contribution

It introduces a method using forbidden electron-nuclear transitions to selectively polarize $^{29}$Si nuclear spins near donors, creating distinct ESR spectral patterns.

Findings

Dynamic polarization via the solid effect creates narrow ESR spectral patterns.

Allowed transition pumping results in a single spectral hole due to rapid spin diffusion.

The method enables targeted initialization of nuclear spin qubits in silicon.

Abstract

We demonstrate an efficient control of $^{29}$Si nuclear spin orientation for specific lattice sites near $^{31}$P donors in silicon crystals at temperatures below 1 K and in high magnetic field of 4.6 T. Excitation of the forbidden electron-nuclear transitions leads to a pattern of narrow holes and peaks in the ESR lines of $^{31}$P. The pattern originates from dynamic polarization the $^{29}$Si nuclear spins near the donors via the solid effect. This method can be used for initialization of qubits based on $^{29}$Si nuclear spins in the all-silicon quantum computer. In comparison, polarization of $^{29}$Si performed by pumping the allowed ESR transitions, did not create any patterns. Instead, a single narrow spectral hole was burnt in the ESR line. The difference is explained by a rapid spin diffusion during the microwave pumping of the allowed transitions.