Silicon T centres offer a path towards utility-scale quantum computing. With their spin-dependent optical emission in the telecommunications O-band, T centre qubits can be linked over long distances, while maintaining information stored locally in their spins. New work published in Physical Review B, in collaboration with our partners at the Silicon Quantum Technology Lab at Simon Fraser University and the Hautier group at Rice University, reports on ‘Silicon T-center hyperfine structure and memory protection schemes.’ This work fully maps the detailed energy level splittings of the T centre under applied magnetic fields, thereby identifying methods to better preserve spin memory while generating remote entanglement. T centres have the ability to emit photons entangled with the spins left behind; longer spin memory would allow more entanglement attempts per qubit without loss of stored quantum information.
This work determines the hyperfine tensor that governs the energy level splittings in the ground state of the T centre, involving the electron spin ‘communications’ qubit and the hydrogen nuclear spin ‘memory’ qubit. These splittings differ depending on magnetic field direction and magnitude. To determine the hyperfine tensor, optically-detected magnetic resonance measurements were taken for magnetic fields of various directions and magnitudes using an isotopically-purified bulk Silicon-28 sample.
In the excited state, the nuclear spin is much more weakly coupled. As a result, the nuclear spin can experience spin flips or phase errors during optical cycles due to the change in hyperfine coupling between the ground and excited states. The T centre hydrogen hyperfine possesses opposite-sign principal values, which allows for elimination of both spin flips and phase errors through magnetic field selection, a trait not common amongst spin-photon interfaces. This work determines the magnetic field such that these errors are asymptotically eliminated for an operational sequence.
Key Takeaways:
- The T centre hydrogen hyperfine tensor has been determined.
- Optically-induced decoherence of T centre nuclear spins can be effectively eliminated through choice of magnetic field.
We would like to acknowledge the contributions of all involved in this research. Read the published paper on Physical Review B or the open-access version on arXiv.
Related content: To discover how T centres in silicon work as spin‑photon qubits, their telecom‑band emission advantage, and how they enable highly scalable quantum systems, read our blog: What Is a T Centre?