High-efficiency vertical emission spin-photon interface for scalable quantum memories

Siavash Mirzaei-Ghormish; Jeddy Bennett; Ryan M. Camacho

doi:10.22331/q-2026-03-20-2035

High-efficiency vertical emission spin-photon interface for scalable quantum memories

Siavash Mirzaei-Ghormish¹, Jeddy Bennett², and Ryan M. Camacho¹

¹Department of Electrical and Computer Engineering, Brigham Young University, Provo, UT
²Department of Mathematics, Brigham Young University, Provo, UT

Published:	2026-03-20, volume 10, page 2035
Editor:	Philipp Schindler
Eprint:	arXiv:2503.20111v2
Doi:	https://doi.org/10.22331/q-2026-03-20-2035
Citation:	Quantum 10, 2035 (2026).

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Abstract

We present an efficient spin-photon interface for free-space vertical emission coupling. Using a dipole model, we show that our design achieves a far-field collection efficiency of 96% at the numerical aperture of 0.7 with a 95% overlap to a Gaussian mode. Our approach is based on a dual perturbation layer design. The first perturbation layer extracts and redirects the resonant mode of a diamond microdisk resonator around the optical axis. The second perturbation layer suppresses side lobes and concentrates most of the light intensity near the center. This dual-layer design enhances control over the farfield pattern and also reduces alignment sensitivity. Additionally, the implemented dipole model performs calculations $3.2$${\times}$$10^6$ times faster than full-wave FDTD simulations. These features make the design promising for quantum information applications.

Popular summary

Quantum networks require devices that can reliably transfer quantum information from a stationary qubit to a traveling photon. Solid-state color centers in diamond are attractive candidates because they can store spin information for long times and emit photons compatible with optical networking. A major challenge, however, is getting those photons out efficiently and in a well-controlled optical mode.

In this work, we propose a nanophotonic interface that addresses this challenge using a diamond microdisk coupled to two vertically stacked grating layers. The device is designed to funnel emission from a color center into a nearly Gaussian beam emitted normal to the chip surface. This vertical geometry is especially attractive for scalable quantum memories, since it is compatible with free-space collection and multiplexed architectures.

Our design combines strong light-matter interaction with efficient out-coupling. Numerical optimization predicts a Purcell enhancement of about 62, collection efficiency up to 96% for a numerical aperture of 0.7, and mode overlap around 95% with an ideal Gaussian beam. The second grating layer plays an important role: besides improving beam quality, it also makes the device more tolerant to emitter misalignment and dipole-orientation uncertainty.

These results suggest that vertically emitting diamond nanophotonic structures could provide an efficient and scalable spin-photon interface for future quantum repeater and quantum memory platforms.

► BibTeX data

@article{MirzaeiGhormish2026highefficiency,
  doi = {10.22331/q-2026-03-20-2035},
  url = {https://doi.org/10.22331/q-2026-03-20-2035},
  title = {High-efficiency vertical emission spin-photon interface for scalable quantum memories},
  author = {Mirzaei-Ghormish, Siavash and Bennett, Jeddy and Camacho, Ryan M.},
  journal = {{Quantum}},
  issn = {2521-327X},
  publisher = {{Verein zur F{\"{o}}rderung des Open Access Publizierens in den Quantenwissenschaften}},
  volume = {10},
  pages = {2035},
  month = mar,
  year = {2026}
}

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