三量子比特纠缠Greenberger-Horne-Zeilinger态和W态的量子线路实现

两个简单的量子线路被提出分别用来制备三量子比特Greenberger-Horne-Zeilinger(GHZ)态和W态。众所周知,任意的多量子比特门都可以由受控非门和单量子比特门复合而成。同样,我们发现三量子比特GHZ态和W态也可以由受控非门和单量子比特门来制备。因此,从量子计算的角度来看我们的方案十分重要。由于在整个过程只用到了单量子比特操作和双量子比特操作,所以我们的方案在实验中很容易实现。     

传送两原子直积态的腔QED方案(英文)

本文提出一个基于原子和腔场共振相互作用传送未知原子直积态的腔QED方案,原子和腔场通过J-C哈密顿量发生共振相互作用.在这个方案里,我们只需要用两个原子接受被传送的原子态以及两个单模腔作为量子通道.该方案既不需要贝尔态测量,也不需要任何操作重构纠缠初态,并且传送成功的概率为100%.这个方案也可以推广到传送n个原子的直积态.     

用W态实现量子隐形传态的腔QED方案

本文提出一个用类W态作为纠缠通道,采用不同于文献[19]的测量基来实现量子隐形传态的腔QED方案.在这个方案里,只需要利用原子和腔场通过J-C哈密顿量发生共振相互作用,一步就可制备纠缠通道.另外,通过原子与腔场的失谐作用,利用Bell态测量,可实现概率为100%的量子隐形传态.在目前的腔QED技术条件下,该方案是可以实现的.     

基于两原子同时和腔场共振作用制备两原子纠缠态的腔QED方案(英文)

我们提出了一个将两个远离的原子制备成纠缠态的腔QED方案,该方案基于两个原子同时和一个腔场发生共振作用.在这个方案里,我们利用一个事先制备好的纠缠态将另外两个分离的原子制备成纠缠态.该方案仅包含两个原子和腔场的共振相互作用,不需要用腔场存储量子信息,并且原子和腔场作用时间极短.因此,我们的方案基于目前的腔QED技术是可以实现的.     

利用SPDC和PBS实现受控非门的有效方案

任意一个N量子比特逻辑运算可以由一系列单量子比特门和受控非门实现[1].因此,这两种量子逻辑门的实现是研究量子计算自然的目标.虽然单量子比特门易于实现,但是由于光子间的相互作用比较弱,所以很难实现受控非门的操作.本文基于T.B.Pittman[2]与A.L. Migdall[3]等人的工作,提出了利用自发参量下转换(SPDC)过程采用多点延时探测触发的方法获得高效单光子源,提高实现受控非门效率的理论方案.     

基于腔QED的隐形传送四比特团簇类态方案

本文提出了一个基于腔QED的隐形传送四比特团簇类态方案,在该方案中选用两个GHZ纠缠对作为量子通道,通过对原子和腔场的大失谐作用以及外加强经典场的辅助,可以制备纠缠的量子通道,完成联合的三粒子测量,成功地实现隐形传送四比特团簇类态。结果还表明,此方案不受腔场退相干和热场的影响.     

实现最优普适1到2实数态量子克隆的方案

提出了基于腔QED的一种实验上可行的方案去实现最优普适1→2实数态量子克隆机制.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.基于当前的腔QED技术,此方案是可以实现的.     

关于多比特电路量子动力学系统中光子自由度的消除方案研究

基于超导传输线和超导量子比特相互耦合的电路量子电动力学（quantumelectrodynamics,QED）系统,是研究固态量子信息和量子测量与控制的理想实验平台．本文在已有工作（单比特电路QED）基础上,进一步研究多比特电路QED系统．具体通过对两比特系统的量子测量和量子控制动力学的模拟,检验了“绝热消除”和“极化子变换”两种消除微腔光子自由度方法的适用条件．和单比特情况不同,我们特别检验了两比特系统Bell纠缠态的“确定性”制备问题．在量子路径水平上模拟发现,由于反馈操作引起量子比特状态翻转,使得极化子变换方法失效,它所导出的“有效测量算符”（其中含有非平庸的“宇称项”）此时也将变得没有意义．     

关于电路量子电动力学系统中光子自由度的消除方案

基于超导传输线和超导量子比特相互耦合的电路量子电动力学(quantum Electrodynamics, QED)系统, 是目前固态量子信息领域的一个倍受关注的物理系统, 也是研究量子测量和量子控制的理想实验平台. 由于其中涉及的驱动场和超导传输线谐振腔支持的光子频率都在微波区, 在量子测量和量子控制研究中往往遇到 大量光子数引起的状态空间维数过大带来的数值模拟方面的困难. 为了避免这个困难, 往往采取"消除"光子自由度的办法, 建立一个只保留量子比特状态自由度的有效描述方案. 本文通过对单比特的量子测量动力学的数值模拟, 检验了 "绝热消除"和"极化子变换"两种方案的适用条件. 结果表明, 在量子非破坏(quantum non-demolition, QND) 测量情况下, 极化子变换精确适用于 任意驱动强度和任意(光子)泄漏速率微腔; 但在非QND测量情况下, 极化子变换相对通常的绝热消除方案, 并无优势. 在强泄漏微腔和弱耦合情况下, 两种消除光子自由度的方法都可以较好地描述 测量动力学; 但如果微腔光子泄漏速率不是很大或量子比特与微腔耦合较强, 则需要纳入光子自由度做完整模拟, 此时的量子测量属性是一个尚待研究的课题.     

实现最优普适1到2实数态量子克隆的方案

提出了基于腔QED的一种实验上可行的方案去实现最优普适1→2 实数态量子克隆机制。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。基于当前的腔QED技术,此方案是可以实现的。     

Implementing Deutsch-Jozsa Algorithm with?Superconducting Quantum Interference Devices in?Cavity QED

We propose a scheme for implementing the Deutsch-Jozsa (DJ) algorithm with superconducting quantum interference devices (SQUIDs) in cavity quantum electrodynamics (QED). The required controlled-NOT (CNOT) operations can be easily realized based on the resonant interaction of SQUIDs with a single-mode high- cavity. The scheme has the advantages of being simple, scalable and feasible in the experimental realization and further utilization.     

Schemes for preparing atomic qubit cluster states in cavity QED

Two schemes are proposed for generating atomic qubits cluster states in cavity quantum electrodynamics (QED). In the first scheme, only two-atom-cavity interactions are involved, and cluster states can be directly generated by using constructed two-qubit controlled phase gates. The second scheme needs the assistance of additional single-qubit rotations, but takes less time than the first one for two-atom operations in the cavity. In this scheme, two projective operators are constructed to prepare two-dimension or more complicated configurations of cluster states. Both schemes are insensitive to the cavity decay due to the fact that the cavity is only virtually excited during the interaction between atoms and the cavity. The idea can also be applied to the ion trap system.     

Approximate Toffoli Gate Originated from a Single Resonant Interaction of Cavity Dissipation and Atomic Spontaneous Emission

We propose a potentially practical scheme to implement an approximate three-qubit Toffoli gate by a single resonant interaction in dissipative cavity QED in which the cavity mode decay and atomic spontaneous emission are considered. The scheme does not require two-qubit controlled-NOT gates but uses a three-qubit phase gate and two Hadamard gates, where the approximate phase gate can be implemented by only a single dissipative resonant interaction of atoms with the cavity mode. Discussions are made for the advantages and the experimental feasibility of our scheme.     

Realization of quantum controlled-NOT gate with resonant interaction

We propose a method for realizing the quantum controlled-NOT gate with a single resonant interaction in cavity QED. Our scheme only requires a single resonant interaction between two atoms and a cavity mode. Thus the scheme is very simple and the quantum dynamics operation can be realized at a high speed, which is important in view of decoherence. In addition, we also show that the gate can be realized in the ion trap system.     

Implementing Deutsch-Jozsa Algorithm in Cavity QED

We propose a simple scheme for implementing Deutsch-Jozsa algorithm in cavity QED. Our scheme is insensitive to both the cavity decay and thermal field because we use the large-detuned interaction. The scheme would be important to constructing practical computer in cavity QED system.     

Multi-state Quantum Teleportation via One Entanglement State

A multi-sender-controlled quantum teleportation scheme is proposed to teleport several secret quantum states from different senders to a distance receiver based on only one Einstein-Podolsky-Rosen (EPR) pair with controlled-NOT (CNOT) gates. In the present scheme, several secret single-qubit quantum states are encoded into a multi-qubit entangled quantum state. Two communication modes, i.e., the detecting mode and the message mode, are employed so that the eavesdropping can be detected easily and the teleported message may be recovered efficiently. It has an advantage over teleporting several different quantum states for one scheme run with more efficiency than the previous quantum teleportation schemes.     

Entanglement Concentration for Three-Atom W State via Introducing an Auxiliary Atom in Cavity QED

We present two physical schemes for concentrating three-atom W state based on the same interaction model which involves two three-level atoms, a cavity field and a classical field. Both schemes introduce only one auxiliary atom. The first scheme involves only one measurement. There is one more measurement on the auxiliary atom in the second scheme, but the interaction time is simple in form and there is no single-qubit operation on the auxiliary atom. Moreover, both schemes are insensitive to cavity decay and within the current cavity quantum electrodynamics (QED) technique.     

Schemes of Implementing a Two-Atom Iswap Gate via Cavity QED

We propose two schemes for implementing a two-atom quantum iswap gate via cavity QED. In the first scheme, only one cavity and two classical fields are used to realizing iswap gate and thus reducing the operating time. The second scheme needs three cavities for atom-cavity interaction and single-qubit rotations without the assistant of the auxiliary level. Our schemes can effectively reduce the cavity decay owing to the reason that the cavity is only virtually excited during the interaction process between atoms and the cavity. Operator fidelity is applied to analyzing the influence when two atoms enter a cavity without accurate simultaneity.     

Teleportation with Tripartite Entangled State via Thermal Cavity

Teleportation schemes with a tripartite entangled state in cavity QED are investigated. The schemes do not need Bell state measurements and the successful probabilities reach optimality. In addition, the schemes are insensitive to both the cavity decay and the thermal field. We first consider two teleportation schemes via a tripartite GHZ state.The first one is a controlled one for an unknown single-qubit state. The second scheme is teleportation of unknown two-atom entangled state. Then we consider teleporting of single-qubit arbitrary state via a tripartite W state.     

Teleportation with Tripartite Entangled State via Thermal Cavity

Teleportation schemes with a tripartite entangled state in cavity QED are investigated. The schemes do not need Bell state measurements and the successful probabilities reach optimality. In addition, the schemes are insensitive to both the cavity decay and the thermal field. We first consider two teleportation schemes via a tripartite GHZ state. The first one is a controlled one for an unknown single-qubit state. The second scheme is teleportation of unknown two-atom entangled state. Then we consider teleporting of single-qubit arbitrary state via a tripartite W state.