Coherent Erbium Spin Defects in Colloidal Nanocrystal Hosts

Kavli Affiliate: Paul Alivisatos

| First 5 Authors: Joeson Wong, Mykyta Onizhuk, Jonah Nagura, Arashdeep S. Thind, Jasleen K. Bindra

| Summary:

We demonstrate nearly a microsecond of spin coherence in Er3+ ions doped in
cerium dioxide nanocrystal hosts, despite a large gyromagnetic ratio and
nanometric proximity of the spin defect to the nanocrystal surface. The long
spin coherence is enabled by reducing the dopant density below the
instantaneous diffusion limit in a nuclear spin-free host material, reaching
the limit of a single erbium spin defect per nanocrystal. We observe a large
Orbach energy in a highly symmetric cubic site, further protecting the
coherence in a qubit that would otherwise rapidly decohere. Spatially
correlated electron spectroscopy measurements reveal the presence of Ce3+ at
the nanocrystal surface that likely acts as extraneous paramagnetic spin noise.
Even with these factors, defect-embedded nanocrystal hosts show tremendous
promise for quantum sensing and quantum communication applications, with
multiple avenues, including core-shell fabrication, redox tuning of oxygen
vacancies, and organic surfactant modification, available to further enhance
their spin coherence and functionality in the future.

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