Purcell enhanced single T centers in silicon nanophotonic cavities*

Distributed entanglement is a key component of quantum communication networks and a means of distributing computation across modular quantum processors. The quality of the entanglement distributed between networked quantum technologies will be contingent upon the quality of their light-matter interconnects. Semiconductor colour centre spin-photon interfaces can be entangled by indistinguishable photon emission and integrated with photonic circuits to form a scalable solid-state quantum information platform. Semiconductor host material silicon is an advanced nanophotonic and microelectronic platform with efficient telecommunications-band emitters, long-lived spin qubits, and some spin-photon interfaces combining both. The silicon T centre is one such promising spin-photon interface with a spin-selective optical transition at 1326 nm (935 meV) within the telecommunications O-band and a local register of electron and nuclear spins with up to 1s coherence times [1].

In this work, we demonstrate single T centres in nanophotonic cavities as a platform for remote entanglement. Nanophotonic cavities can be incorporated into silicon photonic circuits and couple efficiently to low-loss single-mode waveguides, single-photon detectors, modulators, switches, and optical fibres. Thousands of T centre devices are fabricated on chip and screened at room temperature and at 1K using automated measurement routines. Cavity-coupling enhances the T centre optical emission rate by an order of magnitude and increases the emission efficiency to near unity. Instantaneous linewidths of T centre optical transitions in integrated devices are sufficient for high-fidelity remote entanglement. Spectral diffusion from crystal damage and nearby interfaces causes the emission frequency to vary in time and limits remote entanglement rates. We characterize spectral diffusion processes in cavity devices by photon correlation experiments and present techniques for reducing wandering. These results demonstrate that bright telecom spin-photon emitters can be integrated into silicon photonic circuits, paving the way for large-scale telecom-band quantum networks.

[1] L. Bergeron et al. “Silicon-Integrated Telecommunications Photon-Spin Interface”. PRX Quantum (2020)