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arXiv · 2506.17557

Erbium Quantum Memory Platform with Long Optical Coherence via Back-End of Line Deposition on Foundry-Fabricated Photonics

Shobhit Gupta·Robert M. Pettit·Ananthesh Sundaresh·Vasileios Niaouris·Skylar Deckoff-Jones·Daniel P. Crowley·Lewis G. Carpenter·Alan M. Dibos·Manish Kumar Singh·Sean E. Sullivan
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Abstract

Realizing scalable quantum interconnects necessitates the integration of solid-state quantum memories with foundry photonics processes. While prior photonic integration efforts have relied upon specialized, laboratory-scale fabrication techniques, this work demonstrates the monolithic integration of a quantum memory platform with low-loss foundry photonic circuits via back-end-of-line deposition. We deposited thin films of titanium dioxide ($\mathrm{TiO_2}$) doped with erbium (Er) onto silicon nitride nanophotonic waveguides and studied Er optical coherence at sub-Kelvin temperatures with photon echo techniques. We suppressed optical dephasing through ex-situ oxygen annealing and optimized measurement conditions, which yielded an optical coherence time of 64 $\mu$s (a 5 kHz homogeneous linewidth) and slow spectral diffusion of 27 kHz over 4 ms, results that are comparable to state-of-the-art erbium devices. Combined with second-long electron spin lifetimes and demonstrated electrical control of Er emission, our findings establish Er:$\mathrm{TiO_2}$ on foundry photonics as a manufacturable platform for ensemble and single-ion quantum memories.

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Shobhit Gupta, Robert M. Pettit, Ananthesh Sundaresh, Vasileios Niaouris, Skylar Deckoff-Jones, Daniel P. Crowley, Lewis G. Carpenter, Alan M. Dibos, Manish Kumar Singh, Sean E. Sullivan. 2025-06-21. Erbium Quantum Memory Platform with Long Optical Coherence via Back-End of Line Deposition on Foundry-Fabricated Photonics. https://doi.org/10.1103/xj8y-b6sl

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