Efficient Generation of Atomic Singlet State with Rydberg Blockade and Lie-Transform-Based Pulse Design

A protocol to generate atomic singlet state of three atoms is proposed. The strong Rydberg interactions between atoms mediate the multi-qubit operations and help to simplify the dynamics of the system. The effective Hamiltonian is constructed in the regime of Rydberg blockade and the evolution path is built up from an initial state to the target singlet state via the Lie-transform-based pulse design. Numerical simulations show the protocol can produce atomic singlet state with high fidelity and holds robustness against several types of experimental imperfections. Therefore, it may provide some useful results for the generation of singlet states in atomic system.     

Generation of Three-Atom Singlet State with High-Fidelity by Lyapunov Control

International Journal of Theoretical Physics - An effective protocol is proposed to generate three-atom singlet states in an atom-cavity coupled system. By analyzing the interactions between atoms...     

Extraction of singlet states from noninteracting high-dimensional spins

We present a scheme for the extraction of singlet states of two remote particles of arbitrary quantum spin number. The goal is achieved through post-selection of the state of interaction mediators sent in succession. A small number of iterations is sufficient to make the scheme effective. We propose two suitable experimental setups where the protocol can be implemented.     

Spin singlet mott states and evidence for spin singlet quantum condensates of spin-one bosons in lattices

We have investigated spin singlet Mott states of spin-one bosons with antiferromagnetic interactions. These spin singlet states do not break rotational symmetry and exhibit remarkably different macroscopic properties compared with nematic Mott states of spin-one bosons. We demonstrate that the dynamics of spin singlet Mott states is fully characterized by even- or odd-class quantum dimer models. The difference between spin singlet Mott states for even and odd numbers of atoms per site can be attributed to a selection rule in the low energy sectors of on-site Hilbert spaces; alternatively, it can also be attributed to an effect of Berry’s phases on bosonic Mott states. We also discuss evidence for spin singlet quantum condensate of spin-one atoms. Our main finding is that in a projected spin singlet Hilbert space, the low energy physics of spin-one bosons is equivalent to that of a Bose-Hubbard model for spinless bosons interacting via Ising gauge fields. The other major finding is spin-charge separation in some one-dimensional Mott states. We propose charge-e spin singlet superfluid for an odd number of atoms per lattice site and charge-2e spin singlet superfluid for an even number of atoms per lattice site in one-dimensional lattices. All discussions in this article are limited to integer numbers of bosons per site.     

分离状态下的有效纠缠分配

提出采用两个量子比特（四维空间的qudit）作为分离的中间媒介实现高效的纠缠分发方案.首先,两个中间媒介量子比特与两个不同站点的量子比特(定义为a和b)形成四个量子比特非锁定束缚纠缠态,也称为Smolin态.然后,对两个附属量子比特在贝尔基矢上进行联合投影测量,测量结果传送给a和b,基于测量结果,量子比特a和b将可以转换为EPR纠缠态.在整个过程,两个附属量子比特始终与量子比特a和b保持分离.该方案提供了一种利用分离态实现最大纠缠态分发的高效方法,并且给出了公式来描述和理解该过程.     

分离状态下的有效纠缠分配

提出采用两个量子比特(四维空间的qudit)作为分离的中间媒介实现高效的纠缠分发方案.首先,两个中间媒介量子比特与两个不同站点的量子比特(定义为a和b)形成四个量子比特非锁定束缚纠缠态,也称为Smolin态.然后,对两个附属量子比特在贝尔基矢上进行联合投影测量,测量结果传送给a和b,基于测量结果,量子比特a和b将可以转...     

Probability of Color Singlet String States in e + e- → qq + ng at Large Nc Limit

We use the method of color effective Hamiltonian to calculate the probability of color singlet string states at the large N_c limit. We show that a qq + ng system produced from e + e^- annihilation is definitely in color singlet string states when N_c → ∞, i.e., color,singlet string states account for 100% of all possible color singlet states. This justifies the approximation that the hadronization mechanism of each color-neutral flow piece connecting two color-adjacent partons is assumed to be the same as an independent qq singlet system.     

J-Stabilization of singlet states in the solution NMR of multiple-spin systems

Long-lived singlet states have been observed in the solution NMR of spin systems containing more than two coupled spins, despite the fact that the singlet state is expected to be quenched by small long-range J-couplings. We show that the stability of localized singlet states may be explained by taking into account the intra-pair J-coupling between the two spins which participate in the singlet state. The relatively strong intra-pair J-coupling protects the singlet state against quenching by weaker out-of-pair J-couplings.     

三自旋体系长寿命核自旋单重态的制备

长寿命核自旋单重态的寿命（T_S）可以长于常规的纵向弛豫时间（T₁）,基于这个独特的优势,长寿命核自旋单重态具有较好的应用价值.本文对已有脉冲序列进行了改进,给出了适用于任意三自旋弱耦合体系长寿命核自旋单重态制备的参数计算方法,发现在同一个三自旋体系内核自旋单重态具有多种不同比例系数组合的形式,并以丙烯酸为例制备出了两种长寿命核自旋单重态,实验上观察到不同的核自旋单重态的寿命存在差异,另外我们还探究了温度对丙烯酸核自旋单重态寿命的影响.     

用于指导仲氢诱导核极化状态保存的己烯分子中五自旋的单重态制备和寿命研究

仲氢诱导核极化（PHIP）技术能极大地增强核磁共振（NMR）信号的灵敏度,已被应用于磁共振成像、原位化学反应监测等领域．除了不断提高不同分子极化后的灵敏度外,延长和保存高极化度状态对PHIP技术的应用也至关重要,其中将极化后的状态制备成核自旋单重态是目前被研究较多的一种方法．本文以能被PHIP技术极化的己烯分子为研究对象,通过设计优化控制脉冲,对分子中的一个五自旋体系进行操控,制备了多种核自旋单重态,结果表明：己烯分子的碳-碳双键上存在三种不同的核自旋单重态,它们的寿命均长于仲氢极化后产生的初始态的寿命,可以作为延缓极化度衰减的一种中间态;通过对比单重态的寿命与相应自旋的纵向弛豫时间发现,将极化后己烯的状态转化为纵向磁化可能也是一种保存极化度的有效方法．     

Quantum Multi-valued Byzantine Agreement Based on d-dimensional Entangled States

Byzantine agreement has always been an important research topic of distributed computing and has been widely applied to blockchain technology in recent years. We propose a quantum protocol for solving multi-valued detectable Byzantine agreement problem in this paper. Each general is firstly distributed a list that no one else knows based on d-dimensional entangled states. Then the n generals can reach an agreement in which t (where t < n/3) of them are disloyal by using these lists. Finally, it is proved that the list distribution process is secure, and the proposed protocol satisfies the definition of the multi-valued detectable Byzantine agreement.

     

Stability of singlet and triplet trions in carbon nanotubes

We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.6% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band gap energy.     

Quantum Byzantine Agreement with Tripartite Entangled States

We present a quantum protocol for resolving the detectable Byzantine agreement (BA) problem using tripartite Greenberger–Horne–Zeilinger(GHZ)-like states and homodyne measurements in the continuous variable (CV) scenario. The protocol considers the simplest (i.e., three-player) BA problem involving one broadcaster and two receivers who jointly participant in the distribution, test, and agreement phases. The GHZ-like states provide the quantum resources for implementing the primitive of BA and satisfy a priori entanglement bound. Analyses demonstrate that the proposed quantum solution adheres to the agreement, validity, and termination criteria. Conveniently, the beam splitter strategy along with photon detection offers a method for comparing quantum messages. The paper shows that a potential high-efficiency CV-based BA protocol can be achieved using standard off-the-shelf components in quantum optics, maintaining the desirable characteristics of CVs when compared with discrete-variable BA protocol.

     

Infra-red spectrum of water dimer in carbon tetrachloride solution

Geometries of six low-lying excited states of ozone are calculated by a limited SCF-CI procedure and are analysed in detail on the basis of the bonding properties of the molecular orbitals involved in the corresponding excitations. The triplet and singlet A ₂ states are sharply bent with a valence angle of 99°. Differences between triplet and singlet states of same spatial symmetry are also accounted for with special emphasis on the B ₂ states.     

Singlet and triplet bipolarons on the triangular lattice

We study the Coulomb-Fröhlich model on a triangular lattice, looking in particular at states with angular momentum. We examine a simplified model of crab bipolarons with angular momentum by projecting onto the low energy subspace of the Coulomb-Fröhlich model with large phonon frequency. Such a projection is consistent with large long-range electron-phonon coupling and large repulsive Hubbard U. Significant differences are found between the band structure of singlet and triplet states: The triplet state (which has a flat band) is found to be significantly heavier than the singlet state (which has mass similar to the polaron). We test whether the heavier triplet states persist to lower electron-phonon coupling using continuous time quantum Monte Carlo (QMC) simulation. The triplet state is both heavier and larger, demonstrating that the heavier mass is due to quantum interference effects on the motion. We also find that retardation effects reduce the differences between singlet and triplet states, since they reintroduce second order terms in the hopping into the inverse effective mass.     

干涉项对e~+e~-→q+ng两种色连接几率的影响

传统高能e+ e-→hadrons事例产生器普遍采用大Nc 近似 ,使色单态链产生几率达到 10 0 %而色分离态几率为 0 .本文在Nc=3的真实情况下 ,研究了干涉项中颜色部分和动量部分的来源及性质后发现 ,对e+ e-→qq +ng部分子末态中胶子数 2 ,3,干涉项使色单态链产生几率进一步下降到 6 7% ,5 8% ,而n =2时的色分离态几率则增大至不考虑干涉项的 2倍 .由上推断当胶子数n更大时色单态链几率将远小于 1,色分离态几率将更显著增加     

超冷钠原子弹性散射特性的精确计算

基于精确的原子之间相互作用势,系统研究了钠原子在超冷温度下的弹性散射特性,精确计算了钠原子间碰撞时的s波散射长度、有效力程、p波散射长度以及束缚态数目等散射参数.超冷温度下单重态和三重态原子间的弹性散射截面主要为s波贡献,随着碰撞能量的增加散射截面有丰富的形状共振出现,计算发现单重态和三重态散射截面分别存在显著的f波和i波形状共振.应用简并内态近似方法获得了超精细态相互作用时的s波散射长度,所得结果与精确值比较符合.     

基态和单态第一激发态的联氨单分子分解反应的密度泛函研究

本文运用密度泛函B3LYP/6-311+G(3df,2p)方法研究了联氨分子的电子结构和能量,并系统分析了联氨分子的分解反应,计算绘制了单分子联氨在基态和单态第一激发态下沿N-N分解反应的势能曲线。本文计算发现联氨分子在这两种电子态下的离解能分别是：基态58.8 kcal/mol,单态第一激发态495.5 kcal/mol。基态分子分解反应是吸热反应,而单态第一激发态分解反应是放热反应。计算发现单态第一激发态的激发能是554.2 kcal/mol。结合这两种电子态下联氨分子的红外振动频率分析,本文认为,在非强制断键的情况下,联氨分子沿N-N键均裂而生成两个NH2自由基的可能性很小。     

Experimental demonstration of a quantum protocol for byzantine agreement and liar detection

We introduce a new quantum protocol for solving detectable Byzantine agreement (also called detectable broadcast) between three parties, and also for solving the detectable liar detection problem. The protocol is suggested by the properties of a four-qubit entangled state, and the classical part of the protocol is simpler than that of previous proposals. In addition, we present an experimental implementation of the protocol using four-photon entanglement.     

Di-photon Higgs signals at the LHC in the next-to-minimal supersymmetric standard model

The NMSSM contains a Higgs singlet in addition to the two Higgs doublets typical of the MSSM, thus resulting in a total of seven physical Higgs mass states. Therefore, the phenomenology of the NMSSM Higgs sector can differ considerably from that of the MSSM, and there are good prospects of finding in regions of the NMSSM parameter space Higgs signals that cannot be reproduced in the MSSM. We examined here the two-photon decay mode of a Higgs boson and found that up to three neutral Higgs states, heavy and/or light, could be simultaneously observable at the LHC, a possibility precluded to the MSSM. There are also some possibilities that only the lightest NMSSM Higgs boson be detectable via this mode, with a mass beyond the upper limit of the corresponding MSSM state, thus also allowing one to distinguish between the two scenarios. However, in most of the NMSSM parameter space the configurations of the non-minimal model are not very different from those arising in the minimal case.