Silicon-based spin–photon interfaces offer a powerful route toward large-scale quantum computing and quantum networking. A critical ingredient in this vision is an efficient quantum interface, one that converts spin information into photons with high reliability. A new paper, in collaboration with our partners at the Silicon Quantum Technology Lab at Simon Fraser University, advances the understanding of this interface. The paper, “Giant Isotope Effect on the Excited-State Lifetime and Emission Efficiency of the Silicon T Centre,” is now published in Physical Review Letters. This work shows that adding just a single neutron, by replacing protium hydrogen with its heavier isotope, deuterium, can dramatically improve the performance of a colour centre-based quantum interface in silicon.
Why quantum efficiency matters for quantum networks
The silicon T centre is a colour-centre that emits light in the telecommunications band and hosts long-lived electron and nuclear spin qubits. This makes it a promising candidate for spin–photon interfaces: quantum information can be encoded in the electron spin, transferred to a long-lived nuclear spin for storage, and mapped onto telecom photons that distribute entanglement across metropolitan-scale fibre networks or between processors in a quantum computing data centre.
For such architectures to scale, photon generation must be both probable and repeatable. Photons must be emitted with high probability when the T centre is excited, and the same spin must be read out many times, via repeated photon emission, without resetting the entire entanglement process. This requirement is captured by a single key metric: quantum efficiency.
A giant isotope effect
This work shows that the quantum efficiency of the T centre can be improved considerably through isotopic engineering. Replacing the T centre’s protium hydrogen with deuterium increases the observed excited-state lifetime by more than a factor of five. This dramatic change indicates a strong suppression of nonradiative recombination, long recognized as the dominant loss mechanism in protium T centres.
Using first-principles calculations, performed in collaboration with colleagues at the US Naval Research Laboratory, the origin of this effect was identified: the dominant nonradiative decay pathway involves energy transfer to vibrations of the silicon lattice. Substituting protium with the heavier isotope deuterium reduces the vibrational energy of the carbon–hydrogen bond in the defect. As a result, nonradiative decay from the excited state requires the simultaneous excitation of many more vibrational quanta. Therefore, the excited energy is much more likely to be emitted as photons, yielding an emission efficiency approaching 100%.
What this enables
This discovery places the deuterium T centre among the most efficient quantum emitters in silicon. Near-unity emission efficiency directly enhances single-photon sources, spin–photon interfaces, and entanglement distribution protocols, significantly strengthening the case for silicon-based quantum networking and scalable quantum computing architectures.
Key Takeaways
- The giant isotope effect improves T centre lifetime and efficiency
- Vibrational loss is identified as the main limitation
- Near-unity emission efficiency is enabled by deuteration
We gratefully acknowledge the contributions of all collaborators involved in this research. Read the published paper on Physical Review Letters 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?