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Journal of the Optical Society of America B

Spectroscopic investigations of 142Nd3+:YVO4 for quantum memory applications

Peng-Jun Liang, Xiao Liu, Pei-Yun Li, Zong‐Quan Zhou, Chuan‐Feng Li, Guang‐Can Guo

Published Apr 17, 2020• 3 citations
Publisher

Abstract

A Y V O 4 single crystal doped with 142 N d 3 + ions is grown using the Czochralski method. We present systematic spectroscopy measurements of the 4 I 9 / 2 → 4 F 3 / 2 transition of 142 N d 3 + ions at a temperature of 1.5 K. An absorption coefficient of 3.0 m m − 1 is obtained, along with an inhomogeneous broadening below 0.5 GHz. Under a magnetic field of 0.3 T, the optical coherence time and population lifetime are measured as 64 µs and 120 µs, respectively. The ground-state spin relaxation time approaching 11.3 s is determined by spectral hole burning. These results demonstrate the potential for broadband quantum storage using the electron spin levels of this material.

DOI
10.1364/josab.388740

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A Y V O 4 single crystal doped with 142 N d 3 + ions is grown using the Czochralski method. We present systematic spectroscopy measurements of the 4 I 9 / 2 → 4 F 3 / 2 transition of 142 N d 3 + ions at a temperature of 1.5 K. An absorption coefficient of 3.0 m m − 1 is obtained, along with an inhomogeneous broadening below 0.5 GHz. Under a magnetic field of 0.3 T, the optical coherence time and population lifetime are measured as 64 µs and 120 µs, respectively. The ground-state spin relaxation time approaching 11.3 s is determined by spectral hole burning. These results demonstrate the potential for broadband quantum storage using the electron spin levels of this material.
Quantum memory is a crucial element in large-scale quantum networks. Integrated quantum memories based on micro-/-nano structures, such as waveguides, can significantly enhance the scalability and reduce the consumption of optical and electrical power. 151Eu3+:Y2SiO5 stands out as an exceptional candidate material for quantum memory, because it possesses a spin coherence lifetime of 6 h and an optical storage lifetime of 1 h. Here we employ focused ion beam technology to fabricate a triangular nanobeam on the surface of a Y2SiO5 crystal. The width and length of the nanobeam are 2 μm and 20 μm, respectively. The optical lifetime and inhomogeneous broadening of 151Eu3+ in the triangular nanobeam are measured by fluorescence spectroscopy. The optical lifetime is (1.9±0.1) ms and the optical inhomogeneous broadening is (1.58±0.05) GHz at a doping level of 0.07% for 151Eu3+. The hyperfine transition spectra are measured by using optically detected magnetic resonance and spin inhomogeneous broadening of (19±3) kHz is obtained. Furthermore, we analyze the coherence properties of optical and hyperfine transitions, respectively, via transient spectral hole burning and spin echo measurement. We obtain an optical homogeneous linewidth down to (22±3) kHz, which is still limited by the instantaneous spectral diffusion. The spin coherence lifetime under the geomagnetic field is (5.1±0.6) ms. The results demonstrate that 151Eu3+ ions embedded within the 2 μm triangular nanobeam essentially retain the same optical and hyperfine transition properties as those observed in bulk crystals. Consequently, this research lays a foundation for studying the integrated quantum memories based on 151Eu3+ ensembles and the detection of the single 151Eu3+ ion based on the focused ion beam technique.
Rare-earth-ion-doped solids are promising materials as light-matter interfaces for quantum applications. Europium doped into an yttrium orthosilicate crystal in particular has interesting coherence properties and a suitable ground-state energy-level structure for a quantum memory for light. In this paper we report on spectroscopic investigations of this material from the perspective of implementing an atomic frequency comb (AFC)-type quantum memory with spin-wave storage. For this goal we determine the order of the hyperfine levels in the 7F0{}^{7}\phantom{\rule{-0.16em}{0ex}}{F}_{0}7F0​ ground state and 5D0{}^{5}\phantom{\rule{-0.16em}{0ex}}{D}_{0}5D0​ excited state, and we measure the relative strengths of the optical transitions between these levels. We also apply spectral hole burning techniques in order to prepare the system as a well-defined $\ensuremath{\Lambda}$ system, as required for further quantum memory experiments. Furthermore, we measure the optical Rabi frequency on one of the strongest hyperfine transitions, a crucial experimental parameter for the AFC protocol. From this we also obtain a value for the transition dipole moment which is consistent with that obtained from absorption measurements.
Optically addressable solid-state spins have been extensively studied for quantum technologies, offering unique advantages for quantum computing, communication, and sensing. Advancing these applications is generally limited by finding materials that simultaneously provide lifetime-limited optical and long spin coherences. Here, we introduce 171Yb3+ ions doped into a CaWO4 crystal. We perform high-resolution spectroscopy of the excited state, and demonstrate all-optical coherent control of the electron-nuclear spin ensemble. We find narrow inhomogeneous broadening of the optical transitions of 185 MHz and radiative-lifetime-limited coherence time up to 0.75 ms. Next to this, we measure a spin-transition ensemble line width of 5 kHz and electron-nuclear spin coherence time reaching 0.15 seconds at zero magnetic field between 50 mK and 1 K temperatures. These results demonstrate the potential of 171Yb3+:CaWO4 as a low-noise platform for building quantum technologies with ensemble-based memories, microwave-to-optical transducers, and optically addressable single-ion spin qubits. The authors identify 171Yb3+:CaWO4 as a promising material for quantum technological applications, revealing lifetime-limited optical coherence of 0.75 ms and spin coherence of 0.15 s, highlighting its potential for quantum memories and transducers.
Abstract Rare-earth ion-doped crystals are of great interest for quantum memories, a central component in future quantum repeaters. To assess the promise of 1 % Tm3+-doped yttrium gallium garnet (Tm:YGG), we report measurements of optical coherence and energy-level lifetimes of its 3H 6 ↔ 3 H4 transition at a temperature of around 500 mK and various magnetic fields. Using spectral hole burning (SHB), we find hyperfine ground-level (Zeeman level) lifetimes of several minutes at magnetic fields of less than 1000 G. We also measure coherence time exceeding one millisecond using two-pulse photon echoes. Three-pulse photon echo and SHB measurements reveal that due to spectral diffusion, the effective coherence time reduces to a few µs over a timescale of around two hundred seconds. Finally, temporal and frequency-multiplexed storage of optical pulses using the atomic frequency comb protocol is demonstrated. Our results suggest Tm:YGG to be promising for multiplexed photonic quantum memory for quantum repeaters.
Rare-earth ions doped in crystals with low nuclear-spin densities are highly promising candidates for quantum technology applications. In this study, we investigated the spectroscopic properties of the 7F0 - 5 D0 optical and the hyperfine transitions of Eu3+ ions in a CaWO4 crystal, where the nuclear spin arises solely from the 183W isotope, with a natural abundance of 14%. At a temperature of 3 K, we experimentally identified four distinct crystal field environments for Eu3+ ions in a 0.1 at.% Eu3+ doped CaWO4 crystal. The optical coherence properties of Eu3+ ions in these environments were characterized. Additionally, we resolved the hyperfine structures in the 7F0 ground state and 5D0 excited state, and determined the 7F0 ground state lifetimes using spectral hole-burning techniques. These findings highlight the significant potential of Eu3+:CaWO4 for optical quantum memory applications.
We investigate the relevant spectroscopic properties of the 795 nm $^{3}{\mathrm{H}}_{6}\ensuremath{\leftrightarrow}^{3}{\mathrm{H}}_{4}$ transition in 1% ${\mathrm{Tm}}^{3+}\ensuremath{\mathbin:}{\mathrm{Y}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ at temperatures as low as 1.2 K for optical quantum memories based on persistent spectral tailoring of narrow absorption features. Our measurements reveal that this transition has uniform coherence properties over a 56 GHz bandwidth, and a simple hyperfine structure split by $\ifmmode\pm\else\textpm\fi{}44\text{ }\text{ }\mathrm{MHz}/\mathrm{T}$ with lifetimes of up to hours. Furthermore, we find a 3F4{^{3}\mathrm{F}}_{4}3F4​ population lifetime of 64 ms---one of the longest lifetimes observed for an electronic level in a solid---and an exceptionally long coherence lifetime of $490\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$---the longest ever observed for optical transitions of Tm3+{\mathrm{Tm}}^{3+}Tm3+ ions in a crystal. Our results suggest that this material allows realizing broadband quantum memories that enable spectrally multiplexed quantum repeaters.