Rare-earth ions in dielectric crystals are interesting candidates for storing quantum states of photons. A limiting factor on the optical density and thus the conversion efficiency is the distortion introduced in the crystal by doping elements of one type into a crystal matrix of another type. Here, we investigate the system Pr3+:La2(WO4)3, where the similarity of the ionic radii of Pr and La minimizes distortions due to doping. We characterize the praseodymium hyperfine interaction of the ground state (3H4) and one excited state (1D2) and determine the spin Hamiltonian parameters by numerical analysis of Raman-heterodyne spectra, which were collected for a range of static external magnetic field strengths and orientations. On the basis of a crystal field analysis, we discuss the physical origin of the experimentally determined quadrupole and Zeeman tensor characteristics. We show the potential for quantum memory applications by measuring the spin coherence lifetime in a magnetic field that is chosen such that additional magnetic fields do not shift the transition frequency in first order. Experimental results demonstrate a spin coherence lifetime of 158 ms - almost three orders of magnitude longer than in zero field.
The goal of this short note is to show that the formulas I derived originally in [Phys. Rev. A 65, 022308 (2002)] regarding the errors introduced in quantum logical operations by the quantum nature of the control fields apply even in the situation discussed recently by Ozeri et al. in quant-ph/0502063, where the decoherence-inducing spontaneous Raman scattering is considerably suppressed.
Vanadium in silicon carbide (SiC) is emerging as an important candidate system for quantum technology due to its optical transitions in the telecom wavelength range. However, several key characteristics of this defect family including their spin relaxation lifetime (T1), charge state dynamics, and level structure are not fully understood. In this work, we determine the T1 of an ensemble of vanadium defects, demonstrating that it can be greatly enhanced at low temperature. We observe a large spin contrast exceeding 90% and long spin-relaxation times of up to 25s at 100mK, and of order 1s at 1.3…
Er$^{3+}$$:$Y$_2$SiO$_5$ is a material of particular interest due to its suitability for telecom-band quantum memories and quantum transducers interfacing optical communication with quantum computers working in the microwave regime. Extending the coherence lifetimes of the electron spins and the nuclear spins is essential for implementing efficient quantum information processing based on such hybrid electron-nuclear spin systems. The electron spin coherence time of Er$^{3+}$$:$Y$_2$SiO$_5$ is so far limited to several microseconds, and there are significant challenges in optimizing coherence l…
A Raman-Heterodyne Study of the Hyperfine Interaction of the Optically-Excited State $^5$D$_0$ of Eu$^{3+}$:Y$_2$SiO$_5$
在最近的工作中，在Y $_2$ SiO $_5$晶体中的位置1处取代钇的$^{151}$ Eu $^{3+}$的自旋相干时间已延长至6小时[ \textit{Nature} \textbf{517}，177（2015）]。为了使这种长寿命的自旋相干性用于光量子存储器应用，我们使用拉曼外差检测的核磁共振实验表征了光激发态$^5$ D $_0$的超精细相互作用。根据在200个不同取向的磁场中获得的实验谱，拟合了激发态和基态的有效自旋哈密顿量。为了证明拟合参数的正确性和在量子存储协议中的潜在应用，我们还描述了基态超精细相互作用，并预测了产生6小时长的相干时间的临界磁场。得到了临界磁场下$^7$ F $_0$基态和$^5$ D $_0$激发态的完整能级结构。这些结果为量子存储协议的设计和光抽运策略的优化提供了理论依据，为实现长寿命光子量子存储器提供了理论依据。
Long-lifetime coherence in a quantum emitter induced by a metasurface
在原子$V$跃迁的自发发射过程中，各向异性量子真空（AQV）会引起量子干涉[G. S. Agarwal，Phys. Rev. Lett. 84，5500（2000）]。然而，有限的寿命的激发态预计将强烈限制这种现象的可观察性。在本文中，我们预测，AQV可以诱导一个长寿命的相干原子$Λ$ -跃迁的过程中的自发发射，这有一个额外的优点，消除了需要相干激光激发。我们还进行了两个元表面的设计，并比较各自的效率，在远程创建一个AQV。对超表面引起的这种相干性的检测，除了是量子电动力学的另一个证明之外，还可以为量子发射器之间的相干耦合的远程控制铺平道路，这是在量子技术应用中产生纠缠的关键要求。
Progress with quantum technology has for a large part been realized with the nitrogen-vacancy centre in diamond. Part of its properties, however, are nonideal and this drives research into other spin-active crystal defects. Several of these come with much stronger energy scales for spin-orbit and hyperfine coupling, but how this affects their spin coherence is little explored. Vanadium in silicon carbide is such a system, with technological interest for its optical emission at a telecom wavelength and compatibility with semiconductor industry. Here we show coherent spin dynamics of an ensemble…
Hyperfine atomic states are among the most promising candidates for qubit encoding in quantum information processing. In atomic systems, hyperfine transitions are typically driven through a two-photon Raman process by a laser field which is amplitude modulated at the hyperfine qubit frequency. Here, we introduce a new method for generating amplitude modulation by phase modulating a laser and reflecting it from a highly dispersive optical element known as a chirped Bragg grating (CBG). This approach is passively stable, offers high efficiency, and is compatible with high-power laser sources, en…
We demonstrate, for the first time, that a quantum flux parametron (QFP) is capable of acting as both isolator and amplifier in the readout circuit of a capacitively shunted flux qubit (CSFQ). By treating the QFP like a tunable coupler and biasing it such that the coupling is off, we show that $T_1$ of the CSFQ is not impacted by Purcell loss from its low-Q readout resonator ($Q_e = 760$) despite being detuned by only $40$ MHz. When annealed, the QFP amplifies the qubit's persistent current signal such that it generates a flux qubit-state-dependent frequency shift of $85$ MHz in the readout re…
Characterization of the hyperfine interaction of the excited $^5$D$_0$ state of Eu$^{3+}$:Y$_2$SiO$_5$
我们描述了铕（Eu $^{3+}$）超精细相互作用的激发态（$^5$ D $_0$），并确定了它的有效自旋哈密顿参数的塞曼和四极张量.采用光学自由感应衰减方法测量了在弱外磁场（10 mT）下各种磁场方向的超精细分裂。在确定的哈密顿量的基础上，讨论了预测$^7$ F $_{0} \longleftrightarrow ^5$ D $_{0}$跃迁超精细能级间光学跃迁几率的可能性.这些结果为利用$^{151}$ Eu $^{3+}$：Y $_2$ SiO $_5$材料在外磁场下的长自旋相干特性实现光量子存储方案提供了必要的信息
We report microwave spectroscopy of co-trapped $^9\text{Be}^+$ and $^{40}\text{Ca}^+$ within a compact permanent-magnet-based Penning ion trap. The trap is constructed with a reconfigurable array of NdFeB rings providing a 0.654 T magnetic field that is near the 0.6774-T magnetic-field-insensitive hyperfine transition in $^9\text{Be}^+$. Performing Ramsey spectroscopy on this hyperfine transition, we demonstrate nuclear spin coherence with a contrast decay time of >1 s. The $^9\text{Be}^+$ is sympathetically cooled by a Coulomb crystal of $^{40}\text{Ca}^+$, which minimizes $^9\text{Be}^+$ ill…
Nuclear-spin qubits have long coherence time and are desirably applied into quantum information processing. However, the existing methods either fail to address single nucleus (such as nuclear magnetic resonance), or severely affect nuclear coherence time (such as electrical nuclear manipulation based on hyperfine stark effect, ENMHSE). Here we propose an electrical nuclear manipulation called nuclear electric resonance which can on the one hand address the single nuclear qubit, and on the other keep the long coherence time. Applying this, we construct universal quantum gates with external ele…
Tm$^{3+}$:Y$_3$Ga$_5$O$_{12}$ materials for spectrally multiplexed quantum memories
我们研究了795 nm的$^3$ H $_6$ $\leftrightarrow$ $^3$ H $_4$过渡在1%的Tm $^{3+}$：Y $_3$ Ga $_5$ O $_{12}$在温度低至1.2 K的光量子存储器的持续光谱剪裁的基础上窄吸收功能的相关光谱特性。我们的测量结果表明，这种过渡具有均匀的相干性超过56 GHz的带宽，和一个简单的超精细结构分裂的$\pm$ 44 MHz/T的寿命长达数小时。此外，我们发现一个$^3$ F $_4$人口寿命为64毫秒-观察到的最长的寿命在固体中的电子水平之一-和一个非常长的相干寿命为490 $μ$ s -有史以来最长的观察到的Tm $^{3+}$离子在晶体中的光学跃迁。我们的研究结果表明，这种材料允许实现宽带量子存储器，使光谱复用量子中继器。
Hole spins in semiconductors are a potential qubit alternative to electron spins. In nuclear-spin-rich host crystals like GaAs, the hyperfine interaction of hole spins with nuclei is considerably weaker than that for electrons, leading to potentially longer coherence times. Here we demonstrate optical pumping and coherent population trapping for acceptor-bound holes in a strained GaAs epitaxial layer. We find $μ$s-scale longitudinal spin relaxation time T$_1$ and an inhomogeneous dephasing time T$_2^*$ of $\sim$7~ns. We attribute the spin relaxation mechanism to a combination effect of a hole-…
Silicon T centre hyperfine structure and memory protection schemes
Simon Fraser University（西蒙菲莎大学）；Photonic Inc.（Photonic公司）；Thayer School of Engineering, Dartmouth College（达特茅斯学院塔克工程学院）；Leibniz-Institut für Kris（莱布尼茨危机研究所）
Coherence-Based Identification of Carbon-Based Spin Qubits in Hexagonal Boron Nitride from First Principles
SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University（成均馆大学 SKKU 纳米技术高级研究所）；Department of Quantum Information Engineering, Sungkyunkwan University（成均馆大学量子信息工程系）
