Rare earth ions are actively investigated as optically addressable spin systems for quantum technologies thanks to their long optical and spin coherence lifetimes. 171Yb3+, which has 1/2 electron and nuclear spins, recently raised interest for its simple hyperfine structure that moreover can result in long coherence lifetimes at zero magnetic field, an unusual property for paramagnetic rare earth ions. Here, we report on the optical inhomogeneous and homogeneous linewidths in 171Yb3+:Y2SiO5 (site 2) for different doping concentrations. While inhomogeneous linewidth is not correlated to 171Yb3+ concentration, the homogeneous one strongly decreases between 10 and 2 ppm doping level, reaching 255 Hz at 3 K. This is attributed to a slowing down of 171Yb3+ ground state spin flip-flops.
Rare earth ions are actively investigated as optically addressable spin systems for quantum technologies thanks to their long optical and spin coherence lifetimes. 171Yb3+, which has 1/2 electron and nuclear spins, recently raised interest for its simple hyperfine structure that moreover can result in long coherence lifetimes at zero magnetic field, an unusual property for paramagnetic rare earth ions. Here, we report on the optical inhomogeneous and homogeneous linewidths in 171Yb3+:Y2SiO5 (site 2) for different doping concentrations. While inhomogeneous linewidth is not correlated to 171Yb3+ concentration, the homogeneous one strongly decreases between 10 and 2 ppm doping level, reaching 255 Hz at 3 K. This is attributed to a slowing down of 171Yb3+ ground state spin flip-flops.
Rare earth ions are actively investigated as optically addressable spin systems for quantum technologies thanks to their long optical and spin coherence lifetimes. 171Yb3+, which has 1/2 electron and nuclear spins, recently raised interest for its simple hyperfine structure that moreover can result in long coherence lifetimes at zero magnetic field, an unusual property for paramagnetic rare earth ions. Here, we report on the optical inhomogeneous and homogeneous linewidths in 171Yb3+:Y2SiO5 (site 2) for different doping concentrations. While inhomogeneous linewidth is not correlated to 171Yb3+ concentration, the homogeneous one strongly decreases between 10 and 2 ppm doping level, reaching 255 Hz at 3 K. This is attributed to a slowing down of 171Yb3+ ground state spin flip-flops.
Single crystals of 171Yb3+:Y2SiO5 are promising systems for quantum technologies as an efficient optical to spin interface. This is due to the long optical and spin coherence lifetimes, or narrow homogeneous linewidths, observed in this material at zero magnetic field. Inhomogeneous linewidths are also of importance since they affect peak absorption, available bandwidth or spin–spin interactions. In this work, we investigate inhomogeneous linewidths in a series of 171Yb3+:Y2SiO5 single crystals grown by the Czochralski method with the purpose of identifying the broadening mechanisms in the regime of ultra-low doping, i.e. in the ppm range. In a series of samples obtained with varying doping level, growth atmosphere, and cut at different locations in a crystal boule, optical inhomogeneous linewidths between 0.6 and 1.3 GHz are observed. This study suggests that these variations are due to changes in dislocation densities. Spin inhomogeneous linewidths, recorded using electron paramagnetic resonance, did not show the differences between samples observed in the optical domain. They were otherwise found to vary as a function of magnetic field orientation, enabling determination of directions that minimize e.g. detrimental spin–spin interactions. These results suggest ways to reduce optical inhomogeneous linewidths in 171Yb3+:Y2SiO5, which is of interest for high efficiency quantum memories and optical to microwave quantum transducers.
Optical coherence and spin population dynamics in 171Yb3+:Y2SiO5 single crystals
171Yb3+-doped Y2SiO5 crystals are a promising platform for optical quantum memories in long-distance quantum communications. The relevance of this material lies in 171Yb long optical and spin coherence times, along with a large hyperfine splitting, enabling long quantum storage over large bandwidths. Mechanisms affecting the optical decoherence are however not precisely known, especially since low-temperature measurements have so far focused on the 2 to 4 K range. In this work, we performed two- and three-pulse photon echoes and spectral hole burning to determine optical homogeneous linewidths in two 171 Yb:YSO crystals doped at 2 and 10 ppm. Experiments were performed in the 40 mK to 18 K temperature range, leading to linewidths between 320 Hz, among the narrowest reported for rare-earth ions, and several MHz. Our results show that above 6 K the homogeneous linewidth is mainly due to an elastic two-phonon process which results in a slow broadening with temperature, the homogeneous linewidth reaching only 25 kHz at 10 K. At lower temperatures, interactions with 89Yb nuclear spin-flips, paramagnetic defects or impurities, and also Yb-Yb interactions for the higher concentrated crystal, are likely the main limiting factor to the homogeneous linewidth. In particular, we conclude that the direct effect of spin and optical excited state lifetime is a minor contribution to optical decoherence in the whole temperature range studied. Our results indicate possible paths and regimes for further decreasing the homogeneous linewidths or maintaining narrow lines at higher 171Yb concentration.
Rare-earth doped crystals are promising systems for quantum information processing. In particular, paramagnetic rare earths could be used to build coherent interfaces with optical and microwave photons. In addition, isotopes with nonzero nuclear spins could provide long-lived states for quantum state storage and processing. Yb3+ is particularly interesting in this respect since it is the only paramagnetic rare earth with a spin-21 isotope, which corresponds to the simplest possible level structure. In this paper, we report on the optical and magnetic properties of Yb3+ in the two sites of Y2SiO5, a commonly used crystal for quantum applications. We measured optical inhomogeneous linewidths, peak absorption coefficients, oscillator strengths, and excited-state lifetimes. The Zeeman tensors were also determined in the ground and excited states, as well as the ground-state hyperfine tensor for the 171Yb3+ (I=21) isotope. These results suggest that Yb3+:Y2SiO5 is a promising material for applications like solid-state optical and microwave quantum memories.
Rare-earth ion-doped crystals are promising systems for quantum communication and quantum information processing. In particular, paramagnetic rare-earth centers can be utilized to realize quantum coherent interfaces simultaneously for optical and microwave photons. In this paper, we study hyperfine and magnetic properties of a Y2SiO5 crystal doped with 171Yb3+ ions. This isotope is particularly interesting since it is the only rare--earth ion having electronic spin S=21 and nuclear spin I=21, which results in the simplest possible hyperfine level structure. In this work, we determine the hyperfine tensors for the ground and excited states on the optical $^{2}\mathrm{F}_{7/2}(0)\ensuremath{\longleftrightarrow}^{2}\mathrm{F}_{5/2}(0)$ transition by combining spectral hole burning and optically detected magnetic resonance techniques. The resulting spin Hamiltonians correctly predict the magnetic-field dependence of all observed optical-hyperfine transitions, from zero applied field up to fields where the Zeeman interaction is dominating the hyperfine interaction. Using the optical absorption spectrum, we can also determine the order of the hyperfine levels in both states. These results pave the way for realizing solid-state optical and microwave quantum memories based on a 171Yb3+:Y2SiO5 crystal.
Recent progress in the realization of high-quality optical resonators and waveguides along with the possibility to incorporate rare-earth ions, make lithium niobate a promising material to build integrated platforms for quantum information processing. 171Yb3+ is a particularly attractive system because it can show long coherence lifetimes at zero magnetic field thanks to transitions insensitive to magnetic field fluctuations. In this paper, we investigate the optical and spin properties of 171Yb3+ ions in LiNbO3 bulk crystals as well as implanted waveguides. Using hole-burning spectroscopy and optically detected magnetic resonance, we studied ground and excited state hyperfine structures and probed optical and spin spectral holes. Importantly, the hole linewidths suggest that part of the ions in the waveguides are in a similar environment as in the bulk sample. We furthermore characterized spin population relaxation and coherence lifetimes of 171Yb3+ ions in the bulk crystal at temperatures between 50 mK and 9 K. At low temperatures, T2 up to 9.5 $\ensuremath{\mu}\mathrm{s}$ (34 kHz homogeneous linewidth) and spin relaxation rates as long as $\ensuremath{\approx}100$ ms were measured. Our results show that 171Yb3+:LiNbO3 is a system that exhibits narrow optical homogeneous linewidths over a 50 GHz bandwidth together with an electron spin degree of freedom. This is of interest for a variety of applications in integrated quantum photonics such as quantum memories or quantum processors.