Optical coherent transients in 167Er3+ at telecom-band wavelength.

We demonstrate optical coherent transients in a Λ-like hyperfine energy-level system of Er1673+ in yttrium orthosilicate (Y2SiO5) with telecom-band photons at a zero magnetic field. Spectral hole burning was used to study the temperature dependence of the induced spectral antihole. We find that temperatures below 3.0 K suppress population dissipation induced by electron-phonon interactions sufficiently to enable population initialization in the Λ-like system. Further, the pulse area dependence of photoluminescence (PL) from the Λ-like system was measured at 2.2 K. An optical pump power dependence of PL intensity shows Rabi oscillations that contain two full Rabi cycles at the frequency of 2π×810 kHz. A two-pulse photon echo measurement reveals an optical coherence time of 12 µs. To date, this measured optical coherence time is the longest observed for Er3+ in solids at zero magnetic field. These findings will facilitate optical coherent manipulation of Λ-like Er1673+ electronic states as a quantum memories operating at telecom-band wavelengths.

Optically Coherent Nitrogen-Vacancy Centers in Micrometer-Thin Etched Diamond Membranes.

Diamond membrane devices containing optically coherent nitrogen-vacancy (NV) centers are key to enable novel cryogenic experiments such as optical ground-state cooling of hybrid spin-mechanical systems and efficient entanglement distribution in quantum networks. Here, we report on the fabrication of a (3.4 ± 0.2) µm thin, smooth (surface roughness rq < 0.4 nm over an area of 20 µm by 30 µm) diamond membrane containing individually resolvable, narrow linewidth (< 100 MHz) NV centers. We fabricate this sample via a combination of high-energy electron irradiation, high-temperature annealing, and an optimized etching sequence found via a systematic study of the diamond surface evolution on the microscopic level in different etch chemistries. Although our particular device dimensions are optimized for cavity-enhanced entanglement generation between distant NV centers in open, tunable microcavities, our results have implications for a broad range of quantum experiments that require the combination of narrow optical transitions and micrometer-scale device geometry.