Developing the field of quantum information science (QIS) hinges upon designing viable qubits, the smallest unit in quantum computing. One approach to creating qubits is introducing paramagnetic defects into semiconductors or insulators. This class of qubits has seen success in the form of nitrogen-vacancy centers in diamond, divacancy defects in SiC, and P doped into Si. These materials feature paramagnetic defects in a low nuclear spin environment to reduce the impact of nuclear spin on electronic spin coherence. In this work, we report single crystal growth of Ba$_2$CaWO$_{6-δ}$, and the coherence properties of controllably introduced W$^{5+}$ spin centers generated by oxygen vacancies. Ba$_2$CaWO$_{6-δ}$ ($δ$ = 0) is a B-site ordered double perovskite with a temperature-dependent octahedral tilting wherein oxygen vacancies generate W$^{5+}$ (d$^1$), $S = \frac{1}{2}, I$ = 0, centers. We characterized these defects by measuring the spin-lattice ($T_1$) and spin-spin relaxation ($T_2$) times from T = 5 to 150 K. At T = 5 K, $T_1$ = 310 ms and $T_2$ = 4 $μ$s, establishing the viability of these qubit candidates. With increasing temperature, $T_2$ remains constant up to T = 60 K and then decreases to $T_2$ $\approx$ 1 $μ$s at T = 90 K, and remains roughly constant until T = 150 K, demonstrating the remarkable stability of $T_2$ with increasing temperature. Together, these results demonstrate that controlled defect generation in double perovskite structures can generate viable paramagnetic point centers for quantum applications and expand the field of potential materials for QIS.
Coupling between CaWO$_4$ phonons and Er$^{3+}$ dopants
Agency for Science, Technology and Research (A*STAR)（科学与技术研究局）；Centre for Quantum Technologies, National University of Singapore（新加坡国立大学量子技术中心）；Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院物理研究所）；National University of Singapore（新加坡国立大学）；Australian Center for Neutron Scattering, Australian Nuclear Science and Technology Organization（澳大利亚核科学与技术组织中子散射中心）；Paul Scherrer Institut Center for Neutron and Muon Sciences（保罗谢尔研究所中子与μ子科学中心）
We have demonstrated electron-electron and electron-nuclear spin manipulations of Gd3+ ion in CaWO4 crystal. The results suggest that the studied system is perspective for multiqubit implementation in quantum computing.
Erbium-doped crystals offer a versatile platform for hybrid quantum devices because they combine magnetically-sensitive electron-spin transitions with telecom-wavelength optical transitions. At the high doping concentrations necessary for many quantum applications, however, strong magnetic interactions of the electron-spin bath lead to excess spectral diffusion and rapid decoherence. Here we lithographically fabricate a 4.4 GHz superconducting planar micro-resonator on a $\text{CaWO}_{4}$ crystal doped with Er ions at a concentration of twenty parts per million relative to Ca. Using the microw…
In this paper we study a role of F-centers, hole centers and excitons in energy transfer in Eu-doped BaBrI crystals. Optical absorption spectra, thermally stimulated (TSL) and photostimulated (PSL) luminescence in wide temperature range 7-300 K are studied in undoped and doped with different concentrations of Eu ions BaBrI crystals. Based on experimental and calculated results two possible energy transfer processes from host to Eu$^{2+}$ ions are established.
Interface energy and kinetic coefficient of crystal growth strongly depend on the face of the crystalline lattice. To investigate the kinetic anisotropy and velocity of different crystallographic faces we use the hyperbolic (modified) phase field crystal model which takes into account atomic density (as a slow thermodynamic variable) and atomic flux (as a fast thermodynamic variable). Such model covers slow and rapid regimes of interfaces propagation at small and large driving forces during solidification. In example of BCC crystal lattice invading the homogeneous liquid, dynamical regimes of …
Possible mechanism for achieving glass-like thermal conductivities in crystals with off-center atoms
在填充的Ga/Ge包合物中，Eu和Sr在2位偏离中心，而Ba在中心。所有三种填料原子（Ba、Eu、Sr）具有低温爱因斯坦模式;然而仅对于Eu和Sr系统，热导率存在归因于爱因斯坦模式的大的下降。未观察到Ba的下降。在这里，我们认为，这是偏离中心的位移是至关重要的理解这种无法解释的行为差异。对于Eu和Sr体系，它增强了晶格声子与“rattler”运动之间的耦合，并开启/关闭了由偏心位置的存在/不存在而产生的另一种散射机制（1 K < T <20 K）。不同偏离中心位置的随机占据产生高密度的散射声子的破密缺陷。这对提高我们对其他玻璃体系的理解也很重要。
Defects creation and annihilation is a fundamental concept in device fabrication. This report studies the optical bandgap modification in MgO by MeV Ni ion irradiation-induced defect states between valance and conduction band. Ion implantation on MgO single crystal produces substitutional defect states along with F (anionic vacancy center), $F_2$, other oxygen vacancy center and V (cationic vacancy center) centers confirmed from absorption and photoluminescence spectra that can be applied as filament in valance charge memory based resistive random access memories. The variation of optical band…
Single crystals of LiCaAlF6 undoped and Eu, Na co-doped were studied by electron paramagnetic resonance, radioluminescence and thermally stimulated luminescence techniques applied in a correlated manner. The undoped samples exposed to X-ray irradiation exhibited two hole-like charge trapping centers creation, the molecular ions of the form: ClF- and F2^- - F2^- dimer. Their trap depths and frequency factors were determined as follows: Et1=1.7 eV and Et2=1.1. eV for trap depths and f ~ 10^13 s-1 for frequency factor, respectively. It was found that the europium preferable charge state is 2+ in …
Electron and hole trapping was studied in the Ce3+ and Pr3+ doped Lu2Si2O7 scintillation single crystals (LPS:Ce and LPS:Pr) by Electron Paramagnetic Resonance (EPR). Detailed EPR measurements of the X-ray irradiated LPS crystals revealed that holes generated by irradiation are predominantly trapped at oxygen lattice ions creating O- centers. The same X-ray irradiation creates also electron type centers which were attributed to Lu2+ ions, where the trapped electron at Lu lattice ion is stabilized by a defect nearby, such as oxygen vacancy and Ir3+ impurity ion. Both the hole and electron cente…
The processes of hole localization in the Y3Al5O12 and Lu3Al5O12 single crystals were investigated by electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL). It was found that holes created by x-ray irradiation at 77 K are predominantly self-trapped at regular oxygen ions forming O- hole center. This self-trapped hole (STH) center is thermally stable to about 100 K in both YAG and LuAG crystals. At higher temperatures, thermally liberated holes are retrapped at oxygen ions in the vicinity of an acceptor ion such as Mg2+ and Al_{Y} or Al_{Lu} antisite ion that leads t…
To solve the problems of instability and thermal stress birefringence of voltage divided medium in optical voltage sensor (OVS), a half-wave voltage regulation method based on a central symmetry electrode and an arbitrary directional electric field is proposed in this paper. The method uses a center-symmetric copper foil electrode or the ITO (Indium Tin Oxide) transparent electrode to apply voltage, which can arbitrarily adjust the direction of the average electric field in the crystal, so as to improve the half-wave voltage of the bismuth germanate (Bi4Ge3O12, or BGO) crystal directly without…
F+ center, an electron trapped at oxygen vacancy (VO), was investigated in the oxygen deficient Y3Al5O12 (YAG) crystals by EPR. The measurements were performed at temperatures 5-450 K and frequencies 9.4-350 GHz with using both the continue wave and pulse EPR technique. The pulse electron-nuclear double resonance was applied to resolve the hyperfine interaction of the trapped electron with surrounding nuclei. The measurements show that at low temperatures, T < 50 K, EPR spectrum of the F+ center is anisotropic with g factors in the range 1.999-1.988 and originates from three magnetically inequ…
Fluoride crystals doped with rare-earth ions (REI) and pair centers in diamond for fast ($10^{-9}\rm{s}$) quantum computers (FQC) are proposed. As specific systems for REI doping, we propose $Ca_{1-x}Sr_{x}F_{2}$ crystals and their analogues. The $^{4}f$-states with different total orbital angular moments of these ions serve as two-level systems (qubits). Suitable REIs are proposed as well. It is established that the pair $SiV$ and $GeV$ centers in diamond are promising systems for fast optical quantum computers operating at elevated temperatures.
We investigate the effect of nitrogen-vacancy (NV) centers in single crystal diamond on nonlinear optical effects using 40 fs femtosecond laser pulses. The near infrared femtosecond pulses allow us to study purely nonlinear optical effects, such as optical Kerr effect (OKE) and two-photon absorption (TPA), relating to unique optical transitions by electronic structures with NV centers. It is found that both the nonlinear optical effects are enhanced by the introduction of NV centers in the N$^{+}$ dose levels of 2.0$\times$10$^{11}$ and 1.0$\times$10$^{12}$ N$^{+}$/cm$^{2}$. In particular, our…
The current generation of quantum sensing technologies using color centers in diamond crystals is primarily based on the principle that the resonant microwave frequency of the luminescence between quantum levels of the nitrogen-vacancy (NV) center varies with temperature, electric and magnetic fields. This principle enables us to measure, for instance, magnetic and electric fields, as well as local temperature with nanometer resolution in conjunction with a scanning probe microscope (SPM). However, the time resolution of conventional quantum sensing technologies has been limited to microsecond…
Single crystal diamond membranes that host optically active emitters are highly attractive components for integrated quantum nanophotonics. In this work we demonstrate bottom-up synthesis of single crystal diamond membranes containing the germanium vacancy (GeV) color centers. We employ a lift-off technique to generate the membranes and perform chemical vapour deposition in a presence of germanium oxide to realize the insitu doping. Finally, we show that these membranes are suitable for engineering of photonic resonators such as microring cavities with quality factors of 1500. The robust and s…
In this work, we present a 3D Phase Field Dislocation Dynamics (PFDD) model for body-centered cubic (BCC) metals. The model formulation is extended to account for the dependence of the Peierls barrier on the line-character of the dislocation. Simulations of the expansion of a dislocation loop belonging to the $\left\{110\right\} \left<111\right>$ slip system are presented with direct comparison to Molecular Statics (MS) simulations. The extended PFDD model is able to capture the salient features of dislocation loop expansion predicted by MS simulations. The model is also applied to simulate th…
Hybrid quantum photonics combines classical photonics with quantum emitters in a postprocessing step. It facilitates to link ideal quantum light sources to optimized photonic platforms. Optical cavities enable to harness the Purcell-effect boosting the device efficiency. Here, we postprocess a free-standing, crossed-waveguide photonic crystal cavity based on Si$_3$N$_4$ with SiV$^-$ center in nanodiamonds. We develop a routine that holds the capability to optimize all degrees of freedom of the evanescent coupling term utilizing AFM nanomanipulation. After a few optimization cycles we resolve t…
Powered by the mutual developments in instrumentation, materials andtheoretical descriptions, sensing and imaging capabilities of quantum emitters insolids have significantly increased in the past two decades. Quantum emitters insolids, whose properties resemble those of atoms and ions, provide alternative waysto probing natural and artificial nanoscopic systems with minimum disturbance andultimate spatial resolution. Among those emerging quantum emitters, the nitrogen-vacancy (NV) color center in diamond is an outstanding example due to its intrinsicproperties at room temperature (highly-lumi…
We report on the development and application of a parametrized crystal-field model for both C$_{1}$ symmetry centers in trivalent erbium-doped Y$_{2}$SiO$_{5}$. High resolution Zeeman and temperature dependent absorption spectroscopy was performed to acquire the necessary experimental data. The obtained data, in addition to the ground ($^{4}$I$_{15/2}$Z$_{1}$) state and exited ($^{4}$I$_{13/2}$Y$_{1}$) state Zeeman and hyperfine structure, was simultaneously fitted in order to refine an existing crystal-field interpretation of the Er$^{3+}$:Y$_{2}$SiO$_{5}$ system. We demonstrate that it is po…
