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1.
Remote interactions on two distributed quantum systems: nonlocal unambiguous quantum-state discrimination 下载免费PDF全文
Remote quantum-state discrimination is a critical step for the implementation of quantum communication network and distributed quantum computation. We present a protocol for remotely implementing the unambiguous discrimination between nonorthogonal states using quantum entanglements, local operations, and classical communications. This protocol consists of a remote generalized measurement described by a positive operator valued measurement (POVM). We explicitly construct the required remote POVM. The remote POVM can be realized by performing a nonlocal controlled-rotation operation on two spatially separated qubits, one is an ancillary qubit and the other is the qubit which is encoded by two nonorthogonal states to be distinguished, and a conventional local Von Neumann orthogonal measurement on the ancilla. The particular pair of states that can be remotely and unambiguously distinguished is specified by the state of the ancilla. The probability of successful discrimination is not optimal for all admissible pairs. However, for some subset it can be very close to an optimal value in an ordinary local POVM. 相似文献
2.
Two nonlocal and unknown pure qubit states can, with a certain probability of success, be discriminated unambiguously with
the aid of local operations, classical communication, and shared entanglements (LOCCSE). We present a scheme for such kind
of nonlocal unambiguous quantum state discrimination. This scheme consists of a nonlocal positive operator valued measurement
(POVM). This nonlocal POVM can be realized by performing nonlocal unitary operations on initial system and ancillary qubits,
and local von Neumann projective measurements on the ancilla plus initial system. By utilizing the degrees of freedom of the
original system Hilbert space, we need far more simpler operations than those required by the original Neumark approach. We
construct a quantum logic network to implement the required nonlocal POVM. 相似文献
3.
The remote implementation of all possible generalized quantum measurement on single atomic qubit in a quantum network 下载免费PDF全文
To implement generalized quantum measurement (GQM) one has to extend
the original Hilbert space. Generally speaking, the additional
dimensions of the ancilla space increase as the number of the
operators of the GQM n increases. This paper presents a scheme for
deterministically implementing all possible n-operator GQMs on a
single atomic qubit by using only one 2-dimensional ancillary atomic
qubit repeatedly, which remarkably reduces the complexity of the
realistic physical system. Here the qubit is encoded in the internal states
of an atom trapped in an optical cavity and single-photon pulses are
employed to provide the interaction between qubits. It shows that
the scheme can be performed remotely, and thus it is suitable for
implementing GQM in a quantum network. What is more, the number of the
total ancilla dimensions in our scheme achieves the theoretic low
bound. 相似文献
4.
Positive-operator-value-measurement (POVM) is one of the essential components of quantum information processing ( QIP). Recently a 'binary measurement tree' (BST) strategy (PRA 77, 052104) is suggested for implementing arbitrary POVM by sequential two-operator POVMs. We present a simple novel two-operator POVM module via linear optics, which is employed as block to construct a 'binary measurement tree' for implementing arbitrary POVM on single photonic polarization qubit. The total complexity of the experimental setup is significantly reduced in contrast to the previous works. As an example, we give the detailed settings of a well-known POVM. 相似文献
5.
A complete measurement of a quantum observable (POVM) is a measurement of the maximally refined version of the POVM. Complete measurements give information on multiplicities of measurement outcomes and can be used as state preparation procedures. Moreover, any observable can be measured completely. In this Letter, we show that a complete measurement breaks entanglement completely between the system, ancilla and their environment. Finally, consequences for the quantum Zeno effect and complete position measurements are discussed. 相似文献
6.
We report the experimental demonstration of a quantum teleportation protocol with a semiconductor single photon source. Two qubits, a target and an ancilla, each defined by a single photon occupying two optical modes (dual-rail qubit), were generated independently by the single photon source. Upon measurement of two modes from different qubits and postselection, the state of the two remaining modes was found to reproduce the state of the target qubit. In particular, the coherence between the target qubit modes was transferred to the output modes to a large extent. The observed fidelity is 80%, in agreement with the residual distinguishability between consecutive photons from the source. An improved version of this teleportation scheme using more ancillas is the building block of the recent Knill, Laflamme, and Milburn proposal for efficient linear optics quantum computation. 相似文献
7.
Schaetz T Barrett MD Leibfried D Britton J Chiaverini J Itano WM Jost JD Knill E Langer C Wineland DJ 《Physical review letters》2005,94(1):010501
We investigate theoretically and experimentally how quantum state-detection efficiency is improved by the use of quantum information processing (QIP). Experimentally, we encode the state of one 9Be(+) ion qubit with one additional ancilla qubit. By measuring both qubits, we reduce the state-detection error in the presence of noise. The deviation from the theoretically allowed reduction is due to infidelities of the QIP operations. Applying this general scheme to more ancilla qubits suggests that error in the individual qubit measurements need not be a limit to scalable quantum computation. 相似文献
8.
Using two trapped ion species ((27)Al(+) and (9)Be(+)) as primary and ancillary quantum systems, we implement qubit measurements based on the repetitive transfer of information and quantum nondemolition detection. The repetition provides a natural mechanism for an adaptive measurement strategy, which leads to exponentially lower error rates compared to using a fixed number of detection cycles. For a single qubit we demonstrate 99.94% measurement fidelity. We also demonstrate a technique for adaptively measuring multiple qubit states using a single ancilla, and apply the technique to spectroscopy of an optical clock transition. 相似文献
9.
We consider measurements, described by a positive-operator-valued measure (POVM), whose outcome probabilities determine an
arbitrary pure state of a D-dimensional quantum system. We call such a measurement a pure-state informationally complete (PS I-complete) POVM. We show that a measurement with 2D−1 outcomes cannot be PS I-complete, and then we construct a POVM with 2D outcomes that suffices, thus showing that a minimal PS I-complete POVM has 2D outcomes. We also consider PS I-complete POVMs that have only rank-one POVM elements and construct an example with 3D−2 outcomes, which is a generalization of the tetrahedral measurement for a qubit. The question of the minimal number of elements
in a rank-one PS I-complete POVM is left open. 相似文献
10.
We present a scheme for symmetric controlled remote preparation of an arbitrary 2-qudit state form a sender to either of the two receivers via positive operator-valued measurement and pure entangled two-particle states. The first sender transforms the quantum channel shared by all the agents via POVM according to her knowledge of prepared state. All the senders perform singIe- or two-particle projective measurements on their entangled particles and the receiver can probabilisticaly reconstruct the original state on her entangled particles via unitary transformation and auxiliary qubit. The scheme is optimal as the probability which the receiver prepares the original state equals to the entanglement of the quantum channel. Moreover, it is more convenience in application than others as it requires only two-particle entanglements for preparing an arbitrary two-qudit state. 相似文献
11.
Implementation of positive-operator-value measurements for single spin qubit via Heisenberg model 下载免费PDF全文
This paper shows that a proposal for implementing all possible two-operator positive-operator-value measurements of single spin qubit can be obtained via introducing another spin qubit as ancilla. The realization process is accomplished from the free evolution of the Heisenberg XX model by considering nearest-neighbour spin interaction. A controlled-NOT gate, which is a significant operator for this scheme is also constructed and the generalisation to multiple-operator is considered finally. 相似文献
12.
We propose a method to prepare multipartite entangled states such as cluster states and graph states based on the cavity input-output process and single photon measurement. Two quantum gates, a controlled phase gate and a fusion gate between two atoms trapped in respective cavities, are proposed to prepare atomic cluster states and graph states with one and two dimensions. We also introduce a scheme that can generate an arbitrary multipartite photon duster state which uses two coherent states as a qubit basis. 相似文献
13.
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. 相似文献
14.
分离状态下的有效纠缠分配 总被引:1,自引:1,他引:0
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... 相似文献
15.
We give a definition of a universal entangling machine that entangles a system in an unknown state to a specially prepared ancilla. We describe explicitly such a machine for one qubit; i.e., we show how a qubit in an a priori unknown state can be entangled to a four-level ancilla by means of a unitary transformation. As a result, a fixed state-independent amount of entanglement is generated in exchange for a fixed degradation of qubit state fidelity. 相似文献
16.
We propose a concentration scheme of the W class state via cavity QED technique. In our scheme the influences of cavity decay and atomic spontaneous emission have been considered. Furthermore, the atomic spontaneous emission has been suppressed by using non-radiative transitions in atoms with three-level structure, and the photonic qubit is used as flying qubit and atomic qubit as stationary qubit. Therefore our scheme is comparatively easy to realize within techniques presently available. 相似文献
17.
Matsukevich DN Chanelière T Jenkins SD Lan SY Kennedy TA Kuzmich A 《Physical review letters》2006,96(3):030405
We report observations of entanglement of two remote atomic qubits, achieved by generating an entangled state of an atomic qubit and a single photon at site , transmitting the photon to site in an adjacent laboratory through an optical fiber, and converting the photon into an atomic qubit. Entanglement of the two remote atomic qubits is inferred by performing, locally, quantum state transfer of each of the atomic qubits onto a photonic qubit and subsequent measurement of polarization correlations in violation of the Bell inequality [EQUATION: SEE TEXT]. We experimentally determine [EQUATION: SEE TEXT]. Entanglement of two remote atomic qubits, each qubit consisting of two independent spin wave excitations, and reversible, coherent transfer of entanglement between matter and light represent important advances in quantum information science. 相似文献
18.
In this paper, we use three non-maximally GHZ states as the quantum channel and then propose two schemes to realize joint
remotely preparing the general three-qubit state. For the first scheme, we show that the joint remotely state preparation
(JRSP) can be successfully realized with a certain probability by performing information splitting, introducing an ancilla
and proper measurement. Moreover, for the second scheme, we establish a new method to split information which needn’t to introduce
the ancilla on the receiver’s side and can achieve better security. 相似文献
19.
A scheme of a multiqubit quantum computer on atomic ensembles using a quantum transistor implementing two qubit gates is proposed. We demonstrate how multiatomic ensembles permit one to work with a large number of qubits that are represented in a logical encoding in which each qubit is recorded on a superposition of single-particle states of two atomic ensembles. The access to qubits is implemented by appropriate phasing of quantum states of each of atomic ensembles. An atomic quantum transistor is proposed for use when executing two qubit operations. The quantum transistor effect appears when an excitation quantum is exchanged between two multiatomic ensembles located in two closely positioned QED cavities connected with each other by a gate atom. The dynamics of quantum transfer between atomic ensembles can be different depending on one of two states of the gate atom. Using the possibilities of control for of state of the gate atom, we show the possibility of quantum control for the state of atomic ensembles and, based on this, implementation of basic single and two qubit gates. Possible implementation schemes for a quantum computer on an atomic quantum transistor and their advantages in practical implementation are discussed. 相似文献
20.
Teleporting a quantum controlled-Not with one target/two targets gate using two partially entangled states 下载免费PDF全文
This paper considers the teleportation of quantum controlled-Not
(CNOT) gate by using partially entangled states. Different from the
known probability schemes, it presents a method for teleporting a
CNOT gate with unit fidelity and unit probability by using two
partially entangled pairs as quantum channel. The method is
applicable to any two partially entangled pairs satisfying the
condition that their smaller Schmidt coefficients μ and ν
are (2μ + 2ν - 2μν - 1)≥0. In this scheme, the
sender's local generalized measurement described by a positive
operator valued measurement (POVM) lies at the heart. It constructs
the required POVM. It also puts forward a scheme for teleporting a
CNOT with two targets gate with unit fidelity by using same quantum
channel. With assistance of local operations and classical
communications, three spatially separated users are able to complete
the teleportation of a CNOT with two targets gate with probability
of (2μ + 2ν- 1). With a proper value of μ and ν,
the probability could reach nearly 1. 相似文献