Preparation of Cluster States for Many Atoms in Cavity QED

We propose a scheme for the generation of the cluster states for many atoms in cavity QED. In our scheme, the atoms are sent through nonresonant cavity fields in the vacuum states. The cavity fields are only virtually excited and no quantum information will be transferred from the atoms to the cavity fields. The advantage is that the cavities are suppressed during the procedure. The scheme can also be generalized to the ion trap system.     

通过Raman相互作用制备三个腔场的W型纠缠相干态

通过对比分立变量量子信息过程和连续变量量子信息过程的差别,利用相干态比较容易获得的这个特点,提出一种方案制备三个腔场的W型纠缠相干态.方案基于Λ型三能级原子与单模腔场的简并Raman 相互作用.三个相同的腔初始分别处于相干态,三个相同的原子初始处于W型纠缠态,通过三个原子分别与三个腔的Raman相互作用、选择适当的相互作用时间并探测作用后的三个原子,三个腔场坍缩为W型纠缠相干态.在原子与腔的相互作用过程中原子不处于高能级,可以忽略原子的自发辐射,系统的相干性能够得到较好的维持.基于当前的腔量子电动力学技术,相信方案能在实验上实现.该方案制备的三个腔场W型纠缠相干态有望在连续变量量子信息过程中有重要的应用价值.文中将方案推广到制备n(n〉3)个腔场的W型纠缠相干态.     

Possible Realization of Cluster States and Quantum Information Transfer in Cavity QED via Raman Transition

We present a scheme to generate cluster states with many scheme, no transfer of quantum information between the atoms in cavity QED via Raman transition. In this atoms and cavities is required, the cavity fields are only virtually excited and thus the cavity decay is suppressed during the generation of cluster states. The atoms are always populated in the two ground states. Therefore, the scheme is insensitive to the atomic spontaneous emission and cavity decay. We also show how to transfer quantum information from one atom to another.     

Robust scheme for implemention of quantum phase gates for two atoms

We propose a scheme for implementing conditional quantum phase gates for two four-state atoms trapped in a cavity. The two ground states of the atoms are coupled through two Raman processes induced by the cavity mode and two classical fields. Under certain conditions nonresonant Raman processes lead to two-atom coupling and can be used to produce conditional phase gates. The scheme is insensitive to cavity decay, thermal photons, and atomic spontaneous emission. The scheme does not require individual addressing of the atoms.     

Robust generation of high-fidelity entangled states for multiple atoms

A scheme is presented for generating entangled states of multiple atoms in a cavity. In the scheme the atoms simultaneously interact with a cavity mode, with the first atom driven by two classical fields and the other atoms driven by a classical field. Our scheme is valid even if the cavity decay rate is larger than the effective coupling strength, which is important for experiment. The generation of entangled states is conditional on the detection of a photon decaying from the cavity and thus the fidelity of the entangled state is insensitive to the detection inefficiency. Furthermore, the scheme can be applied to the case with any number of atoms in principle.     

Deterministic generation of squeezing for a cavity field with a collection of driven atoms

We propose an efficient scheme for realizing squeezing for a cavity mode. In the scheme, a collection of ladder-type three-level atoms are trapped in a cavity and driven by two classical fields. Under certain conditions, the cavity field deterministically evolves to a squeezed state. The scheme can also be used for conditional generation of superpositions of different squeezed vacuum states.     

Preparation of Highly Squeezed States and Multi—component Entangled Coherent States via the Raman Interaction

A method is presented for generating highly squeezed states of a cavity field via the atom-cavity field interaction of the Raman type.In the scheme a sequence of three-level Λ-type atoms interacts with a cavity field,displaced by a classical source,in a Raman manner.Then the atomic states are measured.By this way the cavity field may collapse onto a superposition of several coherent states,which exhibits strong squeezing.The scheme can also be used to prepare superpositions of many two-mode coherent states for two cavity fields.The coherent states in each mode are on a straight line.This is the first way for preparing multi-component entangled coherent states of this type in cavity QED.     

Entanglement reciprocation using three level atoms in a lambda configuration

We propose a scheme in which entanglement can be transferred from atoms (discrete variables) to entangled states of cavity fields (continuous variables). The cavities play the role of a kind of quantum memory for entanglement, in such a way that it is possible to retrieve it back to the atoms. In our method, two three level atoms in a lambda configuration, previously entangled, are set to interact with single mode cavity fields prepared in coherent states. During the process, one e-bit of entanglement may be deposited in the cavities in an efficient way. We also show that the stored entanglement may be transferred back to flying atoms.     

在腔QED中实现最优非对称经济型1到3的相位协变克隆方案

本文提出一个在腔QED中实验上可行的方案来实现最优非对称经济型1到3相位协变克隆,这种克隆是不需要辅助粒子的。在这个的方案中,三个原子中的两个同时与腔场发生作用,并且它们受经典场的作用。并且此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的。     

腔QED技术实现最优非对称经济型1到3的相位协变克隆方案

本文提出一个在腔QED中实现最优非对称经济型1到3相位协变克隆的可行性方案,这种克隆不需要辅助粒子.在这个方案中,三个原子中的两个同时与腔场发生作用,并且受经典场的作用.此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的.     

利用腔QED技术实现最优非对称经济型1到3的相位协变克隆

本文提出一个在腔QED中实验上可行的方案来实现最优非对称经济型1到3相位协变克隆,这种克隆是不需要辅助粒子的。在这个的方案中,三个原子中的两个同时与腔场发生作用,并且它们受经典场的作用。并且此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的。     

非旋波近似下光场与V型三能级原子依赖强度耦合作用系统中的光场压缩

利用全量子理论,研究了非旋波近似下单模光场与V型三能级原子依赖强度耦合的相互作用系统中光场的压缩效应.结果表明:光场的压缩依赖于系统的本身性质,而虚光子过程使光场的压缩程度明显加强并产生量子噪声,其大小依赖于初始场平均光子数n和光场频率ω,且与原子光场耦合强度g有关.     

Generation correlated four-mode states in cavity QED

A scheme for preparing correlated four-mode states with controllable weighting factors is presented. In the scheme, a sequence of suitably prepared four-level atoms are orderly sent through two bimodal cavities, the detection of all atoms in ground state collapses cavity fields to the desire state. The distinct advantage of our scheme is that the interaction time can be greatly shortened, which is important in view of decoherence.     

Scheme for Preparation of Macroscopic Multi-component Entanglement in Cavity QED

We propose a scheme of generating multi-component entangled coherent states of cavity fields. In this scheme, the atoms pass through cavities one by one, simultaneously driven by a strong classical field in each cavity. Then the detection of the atomic states collapses the cavity fields onto multi-component entangled coherent states. It is shown that, with a judicious choice of the parameters of the classical field, we can conditionally produce macroscopic multi-dimensional maximal entanglement for the cavity modes.     

Probabilistic Teleportation of an Arbitrary Two-mode <Emphasis Type="Italic">N</Emphasis>-photon Entangled State in Cavity QED

We propose a scheme for teleportation of an arbitrary two-mode N-photon entangled states in cavity QED. The scheme is based on the resonant interaction between Λ-type atoms and two-mode cavity fields. In contrast to all the theoretical schemes proposed previously in cavity QED for teleportation of two-mode cavity field states, in the present scheme, the established entanglement for the quantum channel is the type of the multi-dimensional entanglement between the symmetric multi-atom Dicke states and two-mode N-photon states. Therefore, the scheme extends the scope of the theoretical study of the teleportation.     

利用纠缠交换制备原子-原子最大纠缠态

基于腔量子电动力学(QED)提出一种利用两对纠缠的级联型三能级原子与单模腔场系统制备原子-原子最大纠缠态的简单方案,最初两原子之间、两腔场之间互不纠缠,使其中一个原子与一个腔场发生作用,即纠缠交换,该过程仅需对单个腔场态测量就可实现从未有直接作用的两个原子之间的纠缠,精确控制原子与腔场的相互作用时间可获得具有最大保真度的纠缠态.该方案可以延长腔的有效泄漏时间,从而能有效克服光腔的消相干的影响,这样大大降低了系统对腔的品质的要求.     

A Cavity-QED Scheme for Generating Long-Lived Maximally Entangled States

We propose a potentially practical scheme to generate two-atom maximally entangled states by the large-detuning interaction between two three-level ∧-type atoms and coherent optical fields. Conditioned on the results of detecting cavity field, four pairs of atomic maximally entangled states with unity fidelity and high successful probability can be prepared. We also investigate the influence of the cavity dissipation on the generated entangledstates and discuss the experimental feasibility of our scheme.     

Continuous Pump Assisted Conditional Synthesis of Nonclassical States in a Dispersive Cavity QED

The interaction of N identical atoms with both a quantized cavity field and an external classical pumping field with the fields being degenerate in frequency, is studied in the regime where the atoms and fields are highly detuned. This dispersive interaction can be used to generate coherent states for the cavity field. By preparing the injected atoms in a superposition of the bare atomic states, various types of Schroedinger-cat-like states may be generated.     

利用简并Λ型三能级原子与单模腔场的Raman相互作用制备压缩态的叠加态

本文提出利用简并Λ型三能级原子与单模腔场的Raman相互作用制备压缩相干态的叠加态的一种新方案,并对单模压缩相干态光场中有关压缩角(即压缩方向)的控制问题进行了详细讨论.     

Continuous Pump Assisted Conditional Synthesis of Nonclassical States in a Dispersive Cavity QED

The interaction of N identical atoms with both a quantized cavity field and an external classical pumpingfield with the fields being degenerate in frequency, is studied in the regime where the atoms and fields are highly detuned.This dispersive interaction can be used to generate coherent states for the cavity field. By preparing the injected atomsin a superposition of the bare atomic states, various types of Schrodinger-cat-like states may be generated.