Nanoscale systems offer new functionalities in quantum technologies, like single qubit control and detection, or extremely localized sensing. The ability to couple qubits with light is an attractive feature for these systems to enable interfacing with photonic qubits, creating light matter entanglement or fast processing of quantum information. Rare earth ions are promising candidates for this purpose [1-3], as they can show record long optical and spin coherence lifetimes in bulk crystals [4]. However, maintaining these properties at the nanoscale can be challenging, as surface defects for example can cause strong dephasing. Electro-optic storage in rare earth doped nanoparticles.

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In this talk, I will discuss recent results obtained on rare earth doped nanoparticles. First, these materials can be synthesized and processed to show optical and spin coherence lifetimes of in the µs and ms range respectively at low temperature [5,6]. These are unrivaled values for optically addressable spins in a nano-material, leading for example to long, frequency-multiplexed, coherent optical storage [7]. Second, these particles can be placed in high-finesse fiber-based cavities to achieve efficient detection at the single ion level [8]. Combined with rare earth unique coherent properties, this scheme opens the way to quantum memories with single ion processing capabilities, single photon sources or highly scalable quantum processors.

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References:

1. Utikal, T. et al. Spectroscopic detection and state preparation of a single praseodymium ion in a crystal. Nat. Commun. 5, 3627 (2014).

2. Siyushev, P. et al. Coherent properties of single rare-earth spin qubits. Nat. Commun. 5, 3895 (2014).

3. Zhong, T. et al. Nanophotonic rare-earth quantum memory with optically controlled retrieval. Science 357, 1392–9 (2017).

4. Goldner, P., Ferrier, A. & Guillot-Noël, O. in Handbook on the Physics and Chemistry of Rare Earths (eds. Bünzli, J.-C. G. & Pecharsky, V. K.) 46, 1–78 (Elsevier, 2015).

5. Liu, S.; Fossati, A.; Serrano, D.; Tallaire, A.; Ferrier, A.; Goldner, P. Defect Engineering for Quantum Grade Rare-Earth Nanocrystals. ACS Nano 2020, 14 (8), 9953–9962.

6. Serrano, D., Karlsson, J., Fossati, A., Ferrier, A. & Goldner, P. All-optical control of long-lived nuclear spins in rare-earth doped nanoparticles. Nat. Commun. 9, 2127 (2018).

7. Fossati, A.; Liu, S.; Karlsson, J.; Ikesue, A.; Tallaire, A.; Ferrier, A.; Serrano, D.; Goldner, P. A Frequency-Multiplexed Coherent Electro-Optic Memory in Rare Earth Doped Nanoparticles. Nano. Lett., in press, 2020.

8. Casabone, B. et al., Dynamic Control of Purcell Enhanced Emission of Erbium Ions in Nanoparticles. arXiv 2020, quant-ph.