Southwest Quantum Information and Technology

Nanophotonic quantum memory based on rare-earth-doped crystals

Tian Zhong, California Institute of Technology

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Rare earth ions (REIs) are promising candidates for implementing solid-state quantum memories and quantum repeater devices. Moreover, their high spectral stability, long coherence times, and small inhomogeneous broadening make REIs a good choice for integration in an on-chip quantum nano-photonic platform. Here we demonstrate photon storage in an Yttrium orthosilicate Y2SiO5 (YSO) photonic crystal nano-beam resonator with mode volume of 1.6 cubic wavelength. The coupling of the 883 nm 4I9/2-4F3/2 transition of Neodymium (Nd) ions to the nano-resonator results in a 40 fold enhancement of the transition rate (Purcell effect), and increased optical absorption (~80%) - adequate for realizing efficient photon storage via cavity impedance matching. Optical coherence times T2 up to 100 μs with low spectral diffusion were measured for ions embedded in the nano-beams, which are comparable to those observed in unprocessed bulk samples. This indicates that the remarkable coherence properties of REIs are preserved during nanofabrication process. Multi-temporal mode photon storage using stimulated photon echo and atomic frequency comb (AFC) protocols were then implemented in these Nd:YSO nano-resonators. Lastly, our current technology can be readily transferred to Erbium (Er) doped YSO devices, therefore opening the possibility of efficient on-chip optical quantum memory at 1.5 μm telecom wavelength.