Engineered Crystal Systems for Erbium Quantum Hardware

Speaker: Timothy Newman

Affiliation: University of New South Wales

Abstract:

Alice Jeffery, Michael Moull, Angela Liang, Michael Reid, Sven Rogge, John Bartholomew

The ability to send single photons over long distances is required for quantum networks, and also enables tests of fundamental physics. Erbium has optical transitions which couple to telecom-band photons, facilitating single photon transmission over tens of km.

Erbium ions are high performance light-matter interfaces, with a number of groups showing high-purity single photon emission [1], long coherence times [2], and low spectral diffusion in a number of materials [3-4]. However, erbium has a low optical dipole moment, leading to low light-matter coupling. Therefore, a common component of each single ion demonstration is Purcell enhancement: increasing emission with an optical cavity of high quality factor and low mode volume [5-6].

We address the weak dipole through a contrasting approach: engineering a nanoscopic crystalline environment to create designer erbium sites. Our system is a test-bed to develop our understanding of how the crystal field affects optical dipole moment, coherence, and magnetic sensitivity.

We identify sites with optical dipole moments up to 1.63×10^-32 Cm, despite excited state lifetimes over 10 ms and coherence times in excess of 43.9 µs. We present a characterisation of the magnetic sensitivity of three of these. When coupled to a high quality-factor optical resonator, this engineered crystal system will enable a path toward high optical cooperativity.

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[3] Y. Yu et al. Phys. Rev. Lett., vol. 131, no. 17, p. 170801,
[4] J. M. Kindem et al. Nature, vol. 580, no. 7802, pp. 201–204
[5] A. M. Dibos et al. Nano Lett., vol. 22, no. 16, pp. 6530–6536
[6] A. Gritsch et al. Optica, vol. 10, no. 6, p. 783