Abstract
We report on the development of a source of ultra-narrow-band photon pairs using the cavity-enhanced spontaneous parametric down conversion. The photon-pair source has a bandwidth of 265 ± 15 kHz at 606 nm and a spectral brightness of 216 ± 5 pairs/(s · mW · MHz) per longitudinal mode, which could be suitable for Pr3+ ion-based solid-state quantum memories.
Highlights
One of the potential candidates for quantum memories is rare earth ion doped solids (REIDSs), such as Pr3+-doped Y2SiO5 (YSO:Pr) crystals, which have the advantages of long decoherence time, lack of atomic diffusion, and ease of integration
This bandwidth requirement is easy to meet in the case of classical light sources but not in the case of quantum light sources because the natural spectral broadening of quantum light sources, such as single-photon or photon pairs, generated by spontaneous parametric down conversion (SPDC) is in the GHz or THz range
Narrow-band classical light or strongly attenuated coherent light was used in the early light pulse storage experiments
Summary
Quantum memories have attracted considerable attention in recent years in view of their potential for use in quantum communication and quantum computing. One of the potential candidates for quantum memories is rare earth ion doped solids (REIDSs), such as Pr3+-doped Y2SiO5 (YSO:Pr) crystals, which have the advantages of long decoherence time, lack of atomic diffusion, and ease of integration. Heinze et al. have already achieved a storage time of 1 min for classical light pulses in YSO:Pr crystals. One of the potential candidates for quantum memories is rare earth ion doped solids (REIDSs), such as Pr3+-doped Y2SiO5 (YSO:Pr) crystals, which have the advantages of long decoherence time, lack of atomic diffusion, and ease of integration.. For quantum memory based on the electromagnetically induced transparency (EIT) effect, the gradient echo memory, or the atomic frequency comb, the spectral bandwidth requirement for most REIDSs is, in general, of the order of MHz. For example, the spectral linewidth of the hyperfine energy level transition 3H4 ↔ 1D2 of Pr3+ ions in YSO crystals is of the order of 1 MHz; especially, the bandwidth of the EIT window is much less than 1 MHz.. For the storage of light pulses based on the EIT effect in YSO:Pr crystals, a sub-megahertz bandwidth is required. This bandwidth requirement is easy to meet in the case of classical light sources but not in the case of quantum light sources because the natural spectral broadening of quantum light sources, such as single-photon or photon pairs, generated by spontaneous parametric down conversion (SPDC) is in the GHz or THz range. narrow-band classical light or strongly attenuated coherent light was used in the early light pulse storage experiments.
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