A new approach for realization of a quantum interface between single photons and single ions in an ion crystal is proposed and analyzed. In our approach the coupling between a single photon and a single ion is enhanced via the collective degrees of freedom of the ion crystal. Applications including single-photon generation, a memory for a quantum repeater, and a deterministic photon-photon, photon-phonon, or photon-ion entangler are discussed.
Efficient transduction devices that reversibly convert optical and microwave quantum signals into each other are essential for integrating different technologies. Rare-earth ions in solids, and in particular Erbium ions, with both optical and microwave addressable transitions are promising candidates for designing transducers. We propose a microwave-to-optical quantum transducer scheme based on the dark state protocol in $\mathrm{^{167}Er}$ doped into yttrium orthosilicate (YSO) at zero external magnetic fields. Zero-field operation is beneficial for superconducting resonators that can incur e…
Owing to their long excited state lifetimes, rare-earth ions in crystals are widely used in quantum applications. To allow optical readout of the qubit state of individual ions, we propose to dope the crystal with an additional nearby ancilla ion with a shorter radiative lifetime. We show how a Bayesian analysis exhausts the information about the state of the qubit from the optical signal of the ancilla ion. We study the effects of incoherent processes and propose ways to reduce their effect on the readout. Finally, we extend the architecture to ions residing in two remote cavities, and we sho…
We describe a method for creating small quantum processors in a crystal stoichiometric in an optically active rare earth ion. The crystal is doped with another rare earth, creating an ensemble of identical clusters of surrounding ions, whose optical and hyperfine frequencies are uniquely determined by their spatial position in the cluster. Ensembles of ions in each unique position around the dopant serve as qubits, with strong local interactions between ions in different qubits. These ensemble qubits can each be used as a quantum memory for light, and we show how the interactions between qubit…
Time Crystal in the Nonlinear Phonon Mode of the Trapped Ions
Key Laboratory of Materials Physics, Ministry of Education, School of Physics and Laboratory of Zhongyuan Light, Zhengzhou University（郑州大学物理学院、中原之光实验室、教育部材料物理重点实验室）；Institute of Quantum Materials and Physics, Henan Academy of Sciences（河南省科学院量子物质与物理研究所）
Mechanical modes are a potentially useful resource for quantum information applications, such as quantum-level wavelength transducers, due to their ability to interact with electromagnetic radiation across the spectrum. A significant challenge for wavelength transducers is thermomechanical noise in the mechanical mode, which pollutes the transduced signal with thermal states. In this paper, we eliminate thermomechanical noise in the GHz-frequency mechanical breathing mode of a piezoelectric optomechanical crystal using cryogenic cooling in a dilution refrigerator. We optically measure an avera…
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 energy dynamics of non-crystallized (melted) ions, confined in a Paul trap. The non-periodic Coulomb interaction experienced by melted ions forms a medium for non-conservative energy transfer from the radio-frequency (rf) field to the ions, a process known as rf heating. We study rf heating by analyzing numerical simulations of non-crystallized ion motion in Paul trap potentials, in which the energy of the ions' secular motion changes at discrete intervals, corresponding to ion-ion collisions. The analysis of these collisions is used as a basis to derive a simplified model o…
Trapped ions boast long coherence times and excellent gate fidelities, making them a useful platform for quantum information processing. Scaling to larger numbers of ion qubits in RF Paul traps demands great effort. Another technique for trapping ions is via a Penning trap where a 2D crystal of hundreds of ions is formed by controlling the rotation of the ions in the presence of a strong magnetic field. However, the rotation of the ion crystal makes single ion addressability a significant challenge. We propose a protocol that takes advantage of a deformable mirror to introduce AC Stark shift p…
We present a simple Paul trap that stably accommodates up to a couple of dozens of \ensuremath{^{171}\mathrm{Yb}^+~} ions in a stationary two-dimensional lattice. The trap is constructed on a single plate of gold-plated laser-machined alumina and can produce a pancake-like pseudo-potential that makes ions form a self-assembly two-dimensional crystal which locates on the plane composed of axial and one of the transverse axes with around 5 $μ$m spacing. We use Raman laser beams to coherently manipulate these ion-qubits where the net propagation direction is perpendicular to the plane of the crys…
Spin and motion dynamics with zigzag ion crystals in transverse magnetic field gradients
研究了锯齿形离子晶体在横向磁场梯度中的动力学行为。采用表面电极Paul阱来捕获$^{40}$ Ca $^+$离子，并且具有浸没的导线以在离子位置处产生高达16.3（9）T/m的磁场梯度。随着梯度在垂直于最弱约束轴的方向上排列，沿线性离子晶体形成，我们证明了磁场梯度诱导自旋和离子运动之间的耦合。对于三种离子的晶体，通过它们的线性到锯齿形结构转变，我们在用射频场直接驱动自旋时进行边带光谱。此外，我们观察到丰富的激发光谱的振动模式的平面晶体由四个离子。
For conventional ion traps, the trapping potential is close to independent of the electronic state, providing confinement for ions dependent primarily on their charge-to-mass ratio $Q/m$. In contrast, storing ions within an optical dipole trap results in state-dependent confinement. Here we experimentally study optical dipole potentials for $^{138}\mathrm{Ba}^+$ ions stored within two distinctive traps operating at 532 nm and 1064 nm. We prepare the ions in either the $6\mathrm{S}_{\mathrm{1/2}}$ electronic ground or the $5\mathrm{D}_{\mathrm{3/2}}$/ $5\mathrm{D}_{\mathrm{5/2}}$ metastable exc…
Mode shaping in mixed ion crystals of 40Ca2+ and 40Ca+
本文研究了40 Ca ~（2+）和40 Ca ~（2+）离子在线性Paul阱中的混合库仑晶体。用真空紫外激光源将捕获的40 Ca+光电离产生双电荷离子，并通过多普勒冷却的40 Ca+离子进行共振冷却。我们从实验和理论上研究了这些混晶的结构构型和振动模式。我们的结果与40钙2+是一个重要的一步，实验实现的建议，模式成形的线性晶体和自旋相关的配置变化，从锯齿形到线性提出的李等，Phys.Rev.A87，（2013）052304和Phys. Rev. Lett 108，（2012）023003中使用激发到里德堡态的离子。
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.
Thorium ions exhibit unique nuclear properties with high relevance for testing symmetries of nature, and Paul traps feature an ideal experimental platform for performing high precision quantum logic spectroscopy. Loading of stable or long-lived isotopes is well-established and relies on ionization from an atomic beam. A different approach allows trapping short-lived isotopes available as alpha-decay daughters, which recoil from a thin sample of the precursor nuclide. A prominent example is the short-lived $^{229\text{m}}$Th, populated in a decay of long-lived $^{233}$U. Here, ions are provided…
Erbium ions doped into crystals have unique properties for quantum information processing, because of their optical transition at 1.5 $μ$m and of the large magnetic moment of their effective spin-1/2 electronic ground state. Most applications of erbium require however long electron spin coherence times, and this has so far been missing. Here, by selecting a host matrix with a low nuclear-spin density (CaWO$_4$) and by quenching the spectral diffusion due to residual paramagnetic impurities at millikelvin temperatures, we obtain an Er$^{3+}$ electron spin coherence time of 23 ms. This is the lo…
Coulomb crystallization of xenon highly charged ions in a laser-cooled Ca+ matrix
University of Birmingham（伯明翰大学）；Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）；Humboldt-Universität zu Berlin（柏林洪堡大学）；Deutsches Elektronen-Synchrotron (DESY)（德国电子同步辐射中心）；Physikalisch-Technische Bundesanstalt（德国联邦物理技术研究院）
We reported the realization of a $^{174}\mathrm{Yb}^+$-$^{113}\mathrm{Cd}^+$ bi-species Coulomb crystal comprising $^{174}\mathrm{Yb}^+$ ions as coolant and verified its potential for application as a $^{113}\mathrm{Cd}^+$ microwave frequency standard employing sympathetic cooling.The two species of massive ions stably trapped in a Paul trap make up this large two-component crystal. The $^{113}\mathrm{Cd}^+$ ions are trapped in the center, which reduces considerably RF heating and excess micromotion to which the $^{113}\mathrm{Cd}^+$ ions are subjected. Under this scheme, the uncertainty due t…
Most investigations of rare earth ions in solids for quantum information have used rare earth ion doped crystals. Here we analyse the conversion of quantum information from microwave photons to optical frequencies using crystals where the rare earth ions, rather than being dopants, are part of the host crystal. The potential of large ion densities and small linewidths makes such systems very attractive in this application. We show that, as well as high efficiency, large bandwidth conversion is possible. In fact, the collective coupling between the rare earth ions and the optical and microwave …
Simulation of Quantum Magnetism in Mixed Spin Systems with Impurity Doped Ion Crystal
我们提出实现包含不同原子种类的冷离子线性晶体，用于研究自旋系统中的量子相变和阻挫效应，而不是通常讨论的$s=1/2$的情况。离子之间的相互自旋-自旋相互作用可以通过施加具有强梯度的振荡磁场经由塞曼效应来定制。此外，混合离子晶体中的集体振动模式可用于增强和改变自旋-自旋相互作用的强度，甚至将这些力从铁磁性转变为反铁磁性。研究了自旋S=3的高磁矩离子掺杂自旋为1/2的离子晶体中有效自旋-自旋耦合的行为。我们分析了基态相图，并找到不同的自旋顺序，包括亚铁磁态的区域。在最简单的非平凡例子中，我们处理具有$\{1/2,3,1/2}$自旋的线性$\{$ Ca $^+$，Mn $^+$，Ca $^+\}$晶体。为了展示当前最先进实验的可行性，我们讨论了如何使用离子晶体的集体Stern-Gerlach效应和高分辨率光谱来检测量子相位。在此，指示剂自旋1/2离子（物质$^{40}$ Ca $^+$）的状态相关激光诱导荧光也揭示了模拟自旋3离子（$^{50}$ Mn $^+$）的自旋状态，因为这不具有用于光学激发和检测的合适能级。
Ion trap is one of the most promising candidates for quantum computing. Current schemes mainly focus on a linear chain of up to about one hundred ions in a Paul trap. To further scale up the qubit number, one possible direction is to use 2D or 3D ion crystals (Wigner crystals). In these systems, ions are generally subjected to large micromotion due to the strong fast-oscillating electric field, which can significantly influence the performance of entangling gates. In this work, we develop an efficient numerical method to design high-fidelity entangling gates in a general 3D ion crystal. We pre…
The possibility of using mixed crystals highly doped with rare earth ions (REIs) as physical systems for creating fast quantum computers with a sampling time of nanoseconds is discussed. The electronic 4f states of rare earth ions with small values of the diagonal elements of the Judd-Ofelt matrix U(2) are proposed as optical frequency qubit levels. CNOT and other conditional gate operations are performed by exciting the rare earth ion into the 4f state with a large diagonal element of U(2), causing a Stark blockade. It is found that the main interaction responsible for this blockade is the qu…
