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Register a new userOptical coherence and energy-level properties of a Tm$^{3+}$-doped LiNbO$_{3}$ waveguide at sub-Kelvin temperatures
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We characterize the optical coherence and energy-level properties of the 795 nm $^3$H$_6$ to $^3$H$_4$ transition of Tm$^{3+}$ in a Ti$^{4+}$:LiNbO$_{3}$ waveguide at temperatures as low as 0.65 K. Coherence properties are measured with varied temperature, magnetic field, optical excitation power and wavelength, and measurement time-scale. We also investigate nuclear spin-induced hyperfine structure and population dynamics with varying magnetic field and laser excitation power. Except for accountable differences due to difference Ti$^{4+}$ and Tm$^{3+}$-doping concentrations, we find that the properties of Tm$^{3+}$:Ti$^{4+}$:LiNbO$_{3}$ produced by indiffusion doping are consistent with those of a bulk-doped Tm$^{3+}$:LiNbO$_{3}$ crystal measured under similar conditions. Our results, which complement previous work in a narrower parameter space, support using rare-earth-ions for integrated optical and quantum signal processing.
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We characterize the 795 nm $^3$H$_6$ to $^3$H$_4$ transition of Tm$^{3+}$ in a Ti$^{4+}$:LiNbO$_{3}$ waveguide at temperatures as low as 800 mK. Coherence and hyperfine population lifetimes -- up to 117 $mu$s and 2.5 hours, respectively -- exceed those at 3 K at least ten-fold, and are equivalent to those observed in a bulk Tm$^{3+}$:LiNbO$_{3}$ crystal under similar conditions. We also find a transition dipole moment that is equivalent to that of the bulk. Finally, we prepare a 0.5 GHz-bandwidth atomic frequency comb of finesse $>$2 on a vanishing background. These results demonstrate the suitability of rare-earth-doped waveguides created using industry-standard Ti-indiffusion in LiNbO$_3$ for on-chip quantum applications.
Penning ionization reactions in merged beams with precisely controlled collision energies have been shown to accurately probe quantum mechanical effects in reactive collisions. A complete microscopic understanding of the reaction is, however, faced with two major challenges---the highly excited character of the reactions entrance channel and the limited precision of even the best state-of-the-art ab initio potential energy surfaces. Here, we suggest photoassociation spectroscopy as a tool to identify the character of orbiting resonances in the entrance channel and probe the ionization width as a function of inter-particle separation. We introduce the basic concept and discuss the general conditions under which this type of spectroscopy will be successful.
Er:YSO crystal is promising candidate with great variety of its potential applications in quantum information processing and quantum communications ranging from optical/microwave quantum memories to circuit QED and microwave-to-optics frequency converters. Some of the above listed applications require ultra-low temperature environment, i.e. temperatures $Tlesssim0.1~$K. Most of the experiments with erbium doped crystals have been so far carried out at temperatures above 1.5 K. Therefore, only little information is known about Er:YSO coherence properties at millikelvins. Here, we investigate optical decoherence of $^{167}$Er:Y$_2$SiO$_5$ crystal by performing 2- and 3-pulse echo experiments at sub-Kelvin temperature range and at weak and moderate magnetic fields. We show that the deep freezing of the crystal results in an increase of optical coherence time by one order of magnitude below 1.5 Kelvin at the field of $sim$0.2 T. We further describe the detailed investigation of the decoherence mechanisms in this regime.
Er3+:Y2SiO5 is a material of particular interest due to its compatibility in realizing telecom-band optical quantum memories and in the implementation of quantum transducers interfacing optical communication with quantum computers working in the microwave regime. Extending the coherence lifetimes of the electron spins and the nuclear spins is the essential prerequisite for implementing efficient quantum information processing. The electron spin coherence time of this material is so far limited to several microseconds, and there are significant challenges in optimizing coherence lifetimes simultaneously for both the electron and nuclear spins. Here we perform to our knowledge the first pulsed-ENDOR (Electron Nuclear DOuble Resonance) investigation for an Er3+-doped material at sub-Kelvin temperatures, based on a home-built sub-Kelvin pulsed ENDOR spectrometer. At the lowest working temperature, the electron spin coherence time reaches 273 us, which is enhanced by more than 40 times compared with the previous results. In the sub-Kelvin regime, a rapid increase in the nuclear spin coherence time is observed, and the longest coherence time of 738 us is obtained. These results are obtained with the compatibility of fast and efficient operations, which establish the foundation for quantum storage and quantum transduction from microwave to optical frequencies at telecom C-band.
We present a joint experimental and theoretical study of spin coherence properties of 39K, 85Rb, 87Rb, and 133Cs atoms trapped in a solid parahydrogen matrix. We use optical pumping to prepare the spin states of the implanted atoms and circular dichroism to measure their spin states. Optical pumping signals show order-of-magnitude differences depending on both matrix growth conditions and atomic species. We measure the ensemble transverse relaxation times (T2*) of the spin states of the alkali-metal atoms. Different alkali species exhibit dramatically different T2* times, ranging from sub-microsecond coherence times for high mF states of 87Rb, to ~100 microseconds for 39K. These are the longest ensemble T2* times reported for an electron spin system at high densities (n > 10^16 cm^-3). To interpret these observations, we develop a theory of inhomogenous broadening of hyperfine transitions of ^2S atoms in weakly-interacting solid matrices. Our calculated ensemble transverse relaxation times agree well with experiment, and suggest ways to longer coherence times in future work.
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