Physical Review X (Sep 2020)

Coherence Time Extension by Large-Scale Optical Spin Polarization in a Rare-Earth Doped Crystal

  • Sacha Welinski,
  • Alexey Tiranov,
  • Moritz Businger,
  • Alban Ferrier,
  • Mikael Afzelius,
  • Philippe Goldner

DOI
https://doi.org/10.1103/PhysRevX.10.031060
Journal volume & issue
Vol. 10, no. 3
p. 031060

Abstract

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Optically addressable spins are actively investigated in quantum communication, processing, and sensing. Optical and spin coherence lifetimes, which determine quantum operation fidelity and storage time, are often limited by spin-spin interactions, which can be decreased by polarizing spins. Spin polarization can be achieved using optical pumping, large magnetic fields, or mK-range temperatures. Here, we show that optical pumping of a small fraction of ions with a fixed-frequency laser, coupled with spin-spin interactions and spin diffusion, leads to substantial spin polarization in a paramagnetic rare-earth doped crystal, ^{171}Yb^{3+}∶Y_{2}SiO_{5}. Indeed, more than 90% spin polarization has been achieved at 2 K and zero magnetic field. Using this spin polarization mechanism, we further demonstrate an increase in optical coherence lifetime from 0.3 ms to 0.8 ms, due to a strong decrease in spin-spin interactions. This effect opens the way to new schemes for obtaining long optical and spin coherence lifetimes in various solid-state systems such as ensembles of rare-earth ions or color centers in diamond, which are of interest for a broad range of quantum technologies.