We present a qutrit quantum computer design using trapped ions in the presence of a magnetic field gradient. The magnetic field gradient induces a "spin-spin" type coupling, similar to the J-coupling observed in molecules, between the qutrits which allows conditional quantum logic to take place. We describe in some detail, how one can execute specific one and two qutrit quantum gates, required for universal qutrit quantum computing.
High spin magnetic molecules are promising candidates for quantum information processing because they intrinsically have multiple sublevels for information storage and computational operations. However, due to their susceptibility to the environment and limitation from the selection rule, the arbitrary control of the quantum state of a multilevel system on a molecular and electron spin basis has not been realized. Here we exploit the photoexcited triplet of C70 as a molecular electron spin qutrit. After the system was initialized by photoexcitation, we prepared it into representative three-lev…
Optical trapping of molecules with long coherence times is crucial for many protocols in quantum information and metrology. However, the factors that limit the lifetimes of the trapped molecules remain elusive and require improved understanding of the underlying molecular structure. Here we show that measurements of vibronic line strengths in weakly and deeply bound $^{88}$Sr$_2$ molecules, combined with \textit{ab initio} calculations, allow for unambiguous identification of vibrational quantum numbers. This, in turn, enables the construction of refined excited potential energy curves that in…
Atom-molecule collisions in an optically trapped gas
在CO $\_2$激光偶极阱中研究了铯原子与铯$\_2$分子的冷非弹性碰撞.非弹性原子-分子碰撞可以用速率系数$\sim 2.5 \times 10^{-11} $ cm $^3$ s $^{-1}$观测和测量，主要与分子振转态的布居无关。纯原子和分子样品的寿命基本上受到静止气体碰撞的限制。纯分子陷阱的寿命范围为0.3 -1秒，比原子陷阱小四倍，这也是在纯磁陷阱中观察到的。我们给出了分子-分子非弹性碰撞速率的估计为$\sim 10^{-11}$ cm $^{3}$ s $^{-1}$ .
Trapped atoms and ions are among the best controlled quantum systems which find widespread applications in quantum information, sensing and metrology. For molecules, however, a similar degree of control is currently lacking owing to their complex energy-level structure. Quantum-logic protocols in which atomic ions serve as probes for molecular ions are a promising route for achieving this level of control, especially with homonuclear molecules that decouple from black-body radiation. Here, a quantum-non-demolition protocol on single trapped N$_2^+$ molecules is demonstrated. The spin-rovibroni…
Rapid progress in cooling and trapping of molecules has enabled first experiments on high resolution spectroscopy of trapped diatomic molecules, promising unprecedented precision. Extending this work to polyatomic molecules provides unique opportunities due to more complex geometries and additional internal degrees of freedom. Here, this is achieved by combining a homogeneous-field microstructured electric trap, rotational transitions with minimal Stark broadening at a 'magic' offset electric field, and optoelectrical Sisyphus cooling of molecules to the low millikelvin temperature regime. We …
Microwave state transfer and adiabatic dynamics of magnetically trapped polar molecules
具有非零电子角动量的冷和超冷极性分子在量子化学和控制、新量子体系的研究以及精密测量等方面具有重要的意义。然而，在混合电场和磁场中，这些分子一般受到一个大的避免交叉之间的塞曼子级，在磁陷阱，这些交叉导致扭曲的电位和陷阱的电偏置场的损失。我们的特点是这些交叉的OH微波转移捕获的OH分子从上层|f; M = +3/2>奇偶校验状态到较低|e; +3/2>态，并观察了它们在外加偏置电场下的陷阱动力学。我们的观察是很好地描述了一个简单的朗道-齐纳模型，产生洞察力丰富的光谱和动力学的极性自由基在混合外场。
Reaching high densities is a key step towards cold-collision experiments with polyatomic molecules. We use a cryofuge to load up to 2$\times10^7$ CH$_3$F molecules into a box-like electric trap, achieving densities up to 10$^7$/cm$^3$ at temperatures around 350 mK where the elastic dipolar cross-section exceeds 7$\times$10$^{-12}$cm$^2$. We measure inelastic rate constants below 4$\times$10$^{-8}$cm$^3$/s and control these by tuning a homogeneous electric field that covers a large fraction of the trap volume. Comparison to ab-initio calculations gives excellent agreement with dipolar relaxatio…
Quantum computing leverages the quantum resources of superposition and entanglement to efficiently solve computational problems considered intractable for classical computers. Examples include calculating molecular and nuclear structure, simulating strongly-interacting electron systems, and modeling aspects of material function. While substantial theoretical advances have been made in mapping these problems to quantum algorithms, there remains a large gap between the resource requirements for solving such problems and the capabilities of currently available quantum hardware. Bridging this gap …
Helium nanodroplets doped with polar molecules are studied by electrostatic deflection. This broadly applicable method allows even polyatomic molecules to attain sub-Kelvin temperatures and nearly full orientation in the field. The resulting intense force from the field gradient strongly deflects even droplets with tens of thousands of atoms, the most massive neutral systems studied by beam "deflectometry." We use the deflections to extract droplet size distributions. Moreover, since each host droplet deflects according to its mass, spatial filtering of the deflected beam translates into size …
The interaction between the electric dipole moment of a trapped molecular ion and the configuration of the confined Coulomb crystal couples the orientation of the molecule to its motion. We consider the practical feasibility of harnessing this interaction to initialize, process, and read out quantum information encoded in molecular ion qubits without optically illuminating the molecules. We present two schemes wherein a molecular ion can be entangled with a co-trapped atomic ion qubit, providing, among other things, a means for molecular state preparation and measurement. We also show that vir…
Learning symmetry-protected topological order from trapped-ion experiments
Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München（慕尼黑大学阿诺德·索末菲理论物理中心）；Munich Center for Quantum Science and Technology（慕尼黑量子科学与技术中心）；Institute for Experimental Physics, University of Innsbruck（因斯布鲁克大学实验物理研究所）；Institute for Theoretical Physics, University of Innsbruck（因斯布鲁克大学理论物理研究所）；Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences（奥地利科学院量子光学与量子信息研究所）；PlanQC GmbH（PlanQC有限公司）；Alpine Quantum Technologies GmbH（阿尔卑斯量子技术有限公司）
The existence of ideal quantum measurements is one of the fundamental predictions of quantum mechanics. In theory the measurement projects onto the eigenbasis of the measurement observable while preserving all coherences of degenerate eigenstates. The question arises whether there are dynamical processes in nature that correspond to such ideal quantum measurements. Here we address this question and present experimental results monitoring the dynamics of a naturally occurring measurement process: the coupling of a trapped ion qutrit to the photon environment. By taking tomographic snapshots dur…
We measure chemical reactions between a single trapped $^{174}$Yb$^+$ ion immersed in an ultracold bath of $^6$Li atoms containing trace amounts of Li$_2$ dimers. This produces LiYb$^+$ molecular ions that we detect via mass spectrometry. We explain the reaction rates by modelling the dimer density as a function of the magnetic field and obtain excellent agreement when we assume the reaction to follow the Langevin rate. Our results present a novel approach towards the creation of cold molecular ions and point to the exploration of ultracold chemistry in ion molecule collisions. What is more, w…
Error-corrected phase estimation averaged over variable grids on a trapped-ion quantum computer: hyperacuity spectra of a CO molecule adsorbed onto $χ$-Fe$_5$C$_2$
Quemix Inc.（Quemix公司）；Department of Physics, The University of Tokyo（东京大学物理系）；Business Creation Sector R&D Center, MITSUI KINZOKU COMPANY, LIMITED（三井金属株式会社业务创造部门研发中心）；Quantum Materials and Applications Research Center, National Institutes for Quantum Science and Technology (QST)（量子科学技术研究机构量子材料与应用程序研究中心）
