We study the dynamical stability of the entanglement between the two spin ensembles in the presence of an environment. For a comparative study, we consider the two cases: a single spin ensemble, and two ensembles linearly coupled to a bath, respectively. In both circumstances, we assume the validity of the Markovian approximation for the bath. We examine the robustness of the state by means of the growth of the linear entropy which gives a measure of the purity of the system. We find out macroscopic entangled states of two spin ensembles can stably exist in a common bath. This result may be very useful to generate and detect macroscopic entanglement in a common noisy environment and even a stable macroscopic memory.
Entanglement of orbital angular momentum states between an ensemble of cold atoms and a photon
近年来，利用集体增强技术成功地实现了原子系综与单光子的纠缠[D. N. Matsukevich，\textit{et al.}，物理学评论快报。\textbf{95}，040405（2005）.]，其中原子内态和光子偏振态以非局域方式关联。在这里，我们通过实验阐明了在原子系综和光子系统中，也存在着与空间自由度有关的纠缠。讨论了远程原子系综之间高维纠缠的产生及其在凝聚态物理中的应用。
Robust entanglement between a movable mirror and atomic ensemble and entanglement transfer in coupled optomechanical system
提出了一种在光机耦合系统中实现可动镜与原子系综宏观纠缠的方案。在实验上可获得的参数制度，我们表明，在我们的计划中的二分连续变量纠缠的临界温度可以从以前的24 K [Vitali { \it et al.}，物理修订信函\textbf{98}，030405（2007）]和20 K [基因{ \it等人}，Phys. Rev. A \textbf{77}，050307（R）（2008）]至32 K。我们还研究了基于这种耦合系统的纠缠转移。该方案可用于实现连续变量量子信息处理和量子极限位移测量的量子存储器。
It is crucial for physical realization of quantum information networks to first establish entanglement among multiple space-separated quantum memories and then at a user-controlled moment to transfer the stored entanglement to quantum channels for distribution and conveyance of information. Here we present an experimental demonstration on generation, storage and transfer of deterministic quantum entanglement among three spatially separated atomic ensembles. The off-line prepared multipartite entanglement of optical modes is mapped into three distant atomic ensembles to establish entanglement o…
Hybrid matter-photon entanglement is the building block for quantum networks. It is very favorable if the entanglement can be prepared with a high probability. In this paper, we report the deterministic creation of entanglement between an atomic ensemble and a single photon by harnessing Rydberg blockade. We design a scheme that creates entanglement between a single photon's temporal modes and the Rydberg levels that host a collective excitation, using a process of cyclical retrieving and patching. The hybrid entanglement is tested via retrieving the atomic excitation as a second photon and pe…
The Einstein-Podolsky-Rosen (EPR) entanglement is of special importance not only for fundamental research in quantum mechanics, but also for quantum information processing. Establishing EPR entanglement between two memory systems, such as atomic ensembles, nitrogen-vacancy centers, and rare-earth-ion-doped solids is promising for realizing spatial-multimode based quantum communication, quantum computation, and quantum imaging. To date, there have been few reports on realizing EPR entanglement between physical systems in true position and momentum. Here we describe successfully establishing suc…
Macroscopic entanglement distribution with atomic ensembles
East China Normal University（华东师范大学）；Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry RAS（俄罗斯科学院化学物理与医药化学问题联邦研究中心）；Lomonosov Moscow State University（莫斯科罗蒙诺索夫国立大学）；New York University Shanghai（纽约大学上海分校）；Department of Physics, New York University（纽约大学物理系）
Entanglement between a single photon and a matter qubit is an indispensable resource for quantum repeater and quantum networks. With atomic ensembles, the entanglement creation probability is typically very low to inhibit high-order events. In this paper, we propose and experimentally realize a scheme which creates atom-photon entanglement with an intrinsic efficiency of 50%. We make use of Rydberg blockade to generate two collective excitations, lying in separate internal states. By introducing the momentum degree of freedom for the excitations, and interfering them via Raman coupling, we ent…
Random quantum states and operations are of fundamental and practical interests. In this work, we investigate the entanglement properties of random hypergraph states, which generalize the notion of graph states by applying generalized controlled-phase gates on an initial reference product state. In particular, we study the two ensembles generated by random Controlled-Z(CZ) and Controlled-Controlled-Z(CCZ) gates, respectively. By applying tensor network representation and combinational counting, we analytically show that the average subsystem purity and entanglement entropy for the two ensemble…
