Quantum Information Splitting of Arbitrary Three-qubit State by Using Five-qubit Cluster state and GHZ-state

In this paper, a new scheme of quantum information splitting (8QIS) by using five-qubit state and GHZ-state as quantum channel is proposed. The sender Alice performs Bell-state measurements (BSMs) on her qubit-pairs respectively,then tells her measurement result to the receivers Bob. If Bob wants to reconstruct the original states, he must cooperates with the controller Charlie, that Charlie performs two single particle measurement on his qubits and tells Bob the results. According to Alice’s and Bob’s results, Bob can reconstruct the initial state by applying appropriate unitary operation.     

Quantum Secure Direct Communication Based on Four-Qubit Cluster States

A novel quantum secure direct communication scheme based on four-qubit cluster states is proposed. In this scheme, the quantum channel between the sender Alice and the receiver Bob consists of an ordered sequence of cluster states which are prepared by Alice. After ensuring the security of quantum channel, Alice prepares the encoded Bell-state sequence, and performs Bell-basis measurements on the qubits at hand. Then Alice tells the measured results to Bob, and Bob also performs Bell-basis measurements on his own qubits. Finally Bob can get the secret information through the analysis of their measured results. In our scheme, the qubits carrying the secret message do not need to be transmitted in public channel. We show this scheme is determinate and secure.     

控制的量子隐形传态和控制的量子安全直接通信

我们提出了一个控制的量子隐形传态方案。在这方案中，发送方Alice 在监督者Charlie的控制下以他们分享的三粒子纠缠态作为量子通道将二能级粒子未知态的量子信息忠实的传给了遥远的接受方Bob。我们还提出了借助此传态的控制的量子安全直接通信方案。在保证量子通道安全的情况下， Alice直接将秘密信息编码在粒子态序列上，并在Charlie控制下用此传态方法传给Bob。Bob可通过测量他的量子位读出编码信息。由于没有带秘密信息的量子位在Alice 和Bob之间传送，只要量子通道安全， 这种通信不会泄露给窃听者任何信息， 是绝对安全的。这个方案的的特征是双方通信需得到第三方的许可。     

通过纠缠交换实现N粒子任意态的概率传态

量子隐形传态的杰出安全特性使其在未来的通讯领域充满潜力.量子力学的不确定性原理和不可克隆定理禁止对量子态进行直接复制,因此,量子隐形传态将量子态划分为经典和量子两部分,信息分别经由经典和量子通道从发送者Alice传递给远方的接收者Bob,根据这两种信息,Bob实行相应操作就可以以一定的几率重建初始传送态.利用一般意义的隐形传态方案,提出一种简便的新方法实现了一个N粒子任意态的概率传态.方法采用N个非最大纠缠的三粒子GHZ态作为量子通道,避免了引入额外的辅助粒子.为了实现传态,Alice将所有粒子分成N份,对第i份的粒子对(i,x_i)实行Bell测量并将结果通过经典通道通知Bob,Bob对粒子(y_i,z_i)进行相应的操作就可以完成第i个粒子信息的传送.当完成N次相似的重复操作后,Bob就可以准确地重建初始传送态.文中以Bell态测量为基本手段,重复的操作同时也降低了实验难度,作为一个特例,文中给出了一个两粒子任意态的传态方案.     

Bidirectional Controlled Teleportation via Six-Qubit Cluster State

We present a scheme for bidirectional controlled teleportation by using a six-qubit cluster state as quantum channel. Based on the C-not operation and single qubit measurements, Alice may transmit an arbitrary single qubit state of qubit A to Bob and Bob may transmit an arbitrary single qubit state of qubit B to Alice via the control of the supervisor Charlie.     

Bidirectional Controlled Teleportation by Using a Five-Qubit Composite GHZ-Bell State

We present a scheme for bidirectional controlled teleportation by using a five-qubit composite GHZ-Bell state as quantum channel. Based on the C-not operation and single qubit measurements, Alice may transmit an arbitrary single qubit state of qubit A to Bob and Bob may transmit an arbitrary single qubit state of qubit B to Alice via the control of the supervisor Charlie.     

Probabilistic remote state preparation by W states

In this paper we consider a scheme for probabilistic remote state preparation of a general qubit by using W states. The scheme consists of the sender, Alice, and two remote receivers Bob and Carol. Alice performs a projective measurement on her qubit in the basis spanned by the state she wants to prepare and its orthocomplement. This allows either Bob or Carol to reconstruct the state with finite success probability. It is shown that for some special ensembles of qubits, the remote state preparation scheme requires only two classical bits, unlike the case in the scheme of quantum teleportation where three classical bits are needed.     

Bidirectional Quantum Controlled Teleportation via a Maximally Seven-qubit Entangled State

A bidirectional quantum controlled teleportation scheme using a seven-qubit maximally entangled state as quantum channel is proposed. This means that Alice can transmit an arbitrary single qubit state of qubit a to Bob and Bob can transmit an arbitrary single qubit state of qubit b to Alice via the control of the supervisor Charlie.     

Quantum Information Splitting of an Arbitrary Three-Qubit State by Using Cluster States and Bell States

A new application of cluster states is investigated for quantum information splitting (QIS) of an arbitrary three-qubit state. In our scheme, a four-qubit cluster state and a Bell state are shared by a sender (Alice), a controller (Charlie), and areceiver (Bob). Both the sender and controller only need to perform Bell-state measurements (BSMs), the receiver can reconstruct the arbitrary three-qubit state by performing some appropriately unitary transformations on his qubits after he knows the measured results of both the sender and the controller. This QIS scheme is deterministic.     

Bidirectional Quantum Controlled Teleportation of Three-Qubit State by Using GHZ States

In this paper, we present a scheme of bidirectional quantum controlled teleportation of three-qubit state by using GHZ states. Alice transmits an unknown three-qubit entangled state to Bob, and Bob transmit an unknown three-qubit entangled state to Alice via the control of the supervisor Charlie. In order to facilitate the implementation in the experimental environment, the preparation method of quantum channel is given. This scheme is based on that three-qubit entangled state are transformed into two-qubit entangled state and single qubit superposition state by using Toffoli Gate and Controlled-NOT operation, receivers can by introducing the appropriate unitary transformation and auxiliary particles to reconstruct the initial state. Finally, this paper is implemented a scheme of bidirectional quantum controlled teleportation of more than two qubits via the control of the supervisor Charlie.

     

Quantum Splitting a Two-qubit State with a Genuinely Entangled Five-qubit State

A new application of the genuinely entangled five-qubit state is investigated for quantum information splitting of a particular type of two-qubit state. In this scheme, a genuinely entangled five-qubit state is shared by Alice (a sender), Charlie (a controller) and Bob (a receiver), and Alice only needs to perform two Bell-state measurements and Charlie performs a single-qubit measurement, Bob can reconstruct the two-qubit state by performing some appropriately unitary transformations on his qubits after he knows the measured results of both Alice and Charlie. This quantum information splitting scheme is deterministic, i.e. the probability of success is 100 %. The presented protocol is showed to be secure against certain eavesdropping attacks.     

A scheme for secure direct communication using EPR pairs and teleportation

A novel scheme for secure direct communication between Alice and Bob is proposed, where there is no need for establishing a shared secret key. The communication is based on Einstein-Podolsky-Rosen (EPR) pairs and teleportation between Alice and Bob. After insuring the security of the quantum channel (EPR pairs), Bob encodes the secret message directly on a sequence of particle states and transmits them to Alice by teleportation. In this scheme teleportation transmits Bobs message without revealing any information to a potential eavesdropper. Alice can read out the encoded messages directly by the measurement on her qubits. Because there is not a transmission of the qubit which carries the secret message between Alice and Bob, it is completely secure for direct secret communication if perfect quantum channel is used.Received: 17 March 2004, Published online: 30 September 2004PACS: 03.67.Dd Quantum cryptography - 03.67.Hk Quantum communicationF.L. Yan: Present address: Department of Physics, Hebei Normal University, Shijiazhuang 050016, P.R. China     

Quantum Teleportation of the Two-Qubit Entangled State by Use of Four-Qubit Entangled State

In this article, a scheme for quantum teleportation of a two-qubit entangled state using four-qubit cluster state is discussed by use of cavity quantum electrodynamics (QED) involving the interaction of the atoms with the cavity. In this protocol, by using a one-dimensional maximally four-qubit cluster state as quantum channel, quantum information of an unknown state of two two-level particles is faithfully transmitted from a sender (Alice) to a remote receiver (Bob). According to the results measured by the Bob, as it is shown, the unknown two-particle entangled state can be teleported perfectly, and the successful possibilities and fidelities of the scheme can reach 1.0.     

Asymmetric Bidirectional Controlled Teleportation via Seven-qubit Cluster State

We propose a new protocol of asymmetric bidirectional controlled teleportation by using a seven-qubit cluster state as the quantum channel. That is to say Alice wants to transmit an arbitrary single-qubit state to Bob and Bob wants to transmit an arbitrary two qubit state to Alice via the control of the supervisor Charlie. One only need perform the Bell-state measurements and single-qubit measurement.     

A Method for Transferring an Unknown Quantum State and Its Application

We suggest a method for transferring an unknown quantum state. In this method the sender Alice first applies a controlled-not operation on the particle in the unknown quantum state and an ancillary particle which she wants to send to the receiver Bob. Then she sends the ancillary particle to Bob. When Alice is informed by Bob that the ancillary particle is received, she performs a local measurement on her particle and sends Bob the outcome of the local measurement via a classical channel. Depending on the outcome Bob can restore the unknown quantum state, which Alice destroyed, on the ancillary particle successfully. As an application of this method we propose a quantum secure direct communication protocol. By introducing the decoy qubits the security of the scheme is guaranteed.     

Cyclic Controlled Remote Implementation of Partially Unknown Quantum Operations

Fusing the ideas of remote implementation of quantum operation and bidirectional controlled teleportation, we propose a protocol of cyclic controlled remote implementation for three partially unknown quantum operation using seven-qubit cluster state as the quantum channel. Suppose there are three observers Alice, Bob and Charlie, each of them has been given a partially unknown quantum operation. We show that how to realize the cyclic controlled remote implementation of quantum operations where under control of the controller David, Alice can remotely apply her operation on Bob’s qubit, and Bob can remotely apply his operation on Charlie’s qubit, at the same time Charlie can also remotely apply his operation on Alice’s qubit. It is shown that only the senders Alice, Bob, Charlie and the controller David collaborate with each other, the cyclic controlled remote implementation of partially unknown quantum operations can be realized successfully without bidirectional teleportation. So our protocol is safer, resource-efficient and potentially applicable.

     

Non-Maximally Entangled Controlled Teleportation Using Four Particles Cluster States

A new scheme for controlled teleportation with the help of a four-qubit cluster state is proposed. In this scheme, a four-particle cluster state is shared by a sender, a controller and a receiver. The sender first performs a Bell-basis measurement on the qubits at hand, and the controller performs measurements under a non-maximally entangled Bell-basis after he knows the sender’s measurement result. Then the receiver introduces an auxiliary qubit and performs some appropriate unitary transformations on his qubits. Quantum teleportation is realized after the receiver performs a local measurement on the auxiliary qubit and an appropriate unitary transformation on his qubit.     

Circular Controlled Quantum Teleportation by a Genuine Seven-qubit Entangled State

A scheme of circular controlled quantum teleportation, which is a novel version of bidirectional controlled quantum teleportation, is proposed using a specific genuine seven-qubit entangled state as quantum channel, and then it is generalized to the scene with a general genuine seven-qubit entangled state as channel. This means that with the control of the supervisor Daniel while Alice teleportates an unknown qubit state to Bob, Bob can also teleportate an unknown qubit state to Charlie and Charlie can also teleportate an unknown qubit state to Alice circularly, simultaneously. Compared with the BCQT schemes proposed before, the intrinsic efficiency of our scheme is optimal.

     

Fault tolerant three-party quantum secret sharing against collective noise

We present two robust three-party quantum secret sharing protocols against two kinds of collective noise. Each logical qubit is made up of two physical qubits and is invariant under a collective noise. The two agents encode their message on each logical qubit with two unitary physical operations on two physical qubits. As each logical qubit received by each agent can carry two bits of information and the classical information exchanged is reduced largely, these protocols have a high intrinsic efficiency. Moreover, the boss Alice can read out her agents' information with two Bell-state measurements on each four-qubit system, not four-photon joint measurements.     

Efficient quantum key distribution with trines of reference-frame-free qubits

We propose a rotationally-invariant quantum key distribution scheme that uses a pair of orthogonal qubit trines, realized as mixed states of three physical qubits. The measurement outcomes do not depend on how Alice and Bob choose their individual reference frames. The efficient key generation by two-way communication produces two independent raw keys, a bit key and a trit key. For a noiseless channel, Alice and Bob get a total of 0.573 key bits per trine state sent (98% of the Shannon limit). This exceeds by a considerable amount the yield of standard trine schemes, which ideally attain half a key bit per trine state. Eavesdropping introduces an ?-fraction of unbiased noise, ensured by twirling if necessary. The security analysis reveals an asymmetry in Eve's conditioned ancillas for Alice and Bob resulting from their inequivalent roles in the key generation. Upon simplifying the analysis by a plausible symmetry assumption, we find that a secret key can be generated if the noise is below the threshold set by ?=0.197.