Rosen Pairs Research Articles

A rational quantum state sharing protocol with semi-off-line dealer

A rational quantum state sharing protocol with the semi-off-line dealer is proposed. Firstly, the dealer Alice shares an arbitrary two-particle entangled state with the players by Einstein–Podolsky–Rosen (EPR) pairs and Greenberger–Horne–Zeilinger (GHZ) states. The EPR pairs are prepared by Charlie instead of the dealer, reducing the workload of the dealer. Secondly, all players have the same probability of reconstructing the quantum state, guaranteeing the fairness of the protocol. In addition, the dealer is semi-off-line, which considerably reduces the information exchanging between the dealer and the players. Finally, our protocol achieves security, fairness, correctness, and strict Nash equilibrium.

Quantum coordinated multi-point communication based on entanglement swapping

In a quantum network, adjacent nodes can communicate with each other point to point by using pre-shared Einsten---Podolsky---Rosen (EPR) pairs, and furthermore remote nodes can establish entanglement channels by using quantum routing among intermediate nodes. However, with the rapid development of quantum networks, the demand of various message transmission among nodes inevitably emerges. In order to realize this goal and extend quantum networks, we propose a quantum coordinated multi-point communication scheme based on entanglement swapping. The scheme takes full advantage of EPR pairs between adjacent nodes and performs multi-party entanglement swapping to transmit messages. Considering various demands of communication, all nodes work cooperatively to realize different message transmission modes, including one to many, many to one and one to some. Scheme analysis shows that the proposed scheme can flexibly organize a coordinated group and efficiently use EPR resources, while it meets basic security requirement under the condition of coordinated communication.

ENTANGLEMENT BETWEEN CHARGE AND FLUX QUBITS

Following the scheme proposed by X. L. He et al. [Phys. Rev. B76 (2007) 024517], we investigate the generation of a maximally entangled state between the charge and flux qubits. It is shown that macroscopic Einstein–Podolsky–Rosen (EPR) pairs can be created and the entanglement can be long-lived. Since the large Josephson junction is only virtually excited, no quantum information will be transferred from the charge and flux qubits to the large Josephson junction. Based on the strong inductive coupling, a fast entanglement operation can be achieved.

Quantum private comparison of equality protocol without a third party

This paper presents a novel quantum private comparison protocol that uses Einstein---Podolsky---Rosen pairs. The proposed protocol allows two parties to secretly compare their information without exposing their actual contents. The technique of entanglement swapping enables the comparison to be achieved without the help of a third party. Moreover, because the proposed protocol employs one-step transmission and decoy photons, it is secure against the various quantum attacks in existence thus far.

NEW ARBITRATED QUANTUM SIGNATURE WITH MESSAGE RECOVERY

Recently, Lee proposed two quantum signature schemes with message recovery. This paper shows insecurity in their schemes such that the scheme could be repudiated by the receiver Bob. Then, this paper proposes an arbitrated quantum signature scheme based on the correlation of Einstein–Podolsky–Rosen (EPR) pairs. Compared with Lee's scheme, the new scheme not only maintains the advantages of the original scheme but offers a higher efficiency in transmission and it can also avoid being disavowed by the receiver.

QUANTUM SECURE DIRECT COMMUNICATION WITH A CONSTANT NUMBER OF EPR PAIRS

In this paper, we propose a quantum secure direct communication (QSDC) protocol based on Einstein–Podolsky–Rosen (EPR) pairs. Previous QSDC protocols usually consume one EPR pair to transmit a single qubit. If Alice wants to transmit an n-bit message, she needs at least n/2 EPR pairs when a dense coding scheme is used. In our protocol, if both Alice and Bob preshare 2c + 1 EPR pairs with the trusted server, where c is a constant, Alice can transmit an arbitrary number of qubits to Bob. The 2c EPR pairs are used by Alice and Bob to authenticate each other and the remaining EPR pair is used to encode and decode the message qubit. Thus the total number of EPR pairs used for one communication is a constant no matter how many bits will be transmitted. It is not necessary to transmit EPR pairs before transmitting the secret message except for the preshared constant number of EPR pairs. This reduces both the utilization of the quantum channel and the risk. In addition, after the authentication, the server is not involved in the message transmission. Thus we can prevent the server from knowing the message.

QUANTUM SECURE DIRECT COMMUNICATION WITH ONLY SEPARATE MEASUREMENTS IN DRIVEN CAVITY QED

An experimentally feasible new scheme for quantum secure direct communication is proposed in cavity quantum electrodynamics without apparent joint Bell-state measurement. The legitimate user can receive different secret messages in a direct way through Einstein–Podolsky–Rosen (EPR) pairs, the probability of the success in our scheme is unity. In the communication processes, the interactions between atoms and a single-mode non-resonant cavity with the assistance of a strong classical driving field substitute the joint measurements. Hence, this scheme needs only separate measurements. In addition, the scheme is insensitive to the cavity decay and the thermal field. The discussion of the scheme indicates that it can be realized based on current technologies.

An efficient quantum secure direct communication scheme with authentication

In this paper an efficient quantum secure direct communication (QSDC) scheme with authentication is presented, which is based on quantum entanglement and polarized single photons. The present protocol uses Einstein–Podolsky–Rosen (EPR) pairs and polarized single photons in batches. A particle of the EPR pairs is retained in the sender's station, and the other is transmitted forth and back between the sender and the receiver, similar to the ``ping–pong'' QSDC protocol. According to the shared information beforehand, these two kinds of quantum states are mixed and then transmitted via a quantum channel. The EPR pairs are used to transmit secret messages and the polarized single photons used for authentication and eavesdropping check. Consequently, because of the dual contributions of the polarized single photons, no classical information is needed. The intrinsic efficiency and total efficiency are both 1 in this scheme as almost all of the instances are useful and each EPR pair can be used to carry two bits of information.

Teleportation of a two-atom entangled state using a single EPR pair in cavity QED

We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics (QED). In the scheme, we choose a single Einstein–Podolsky–Rosen (EPR) pair as the quantum channel which is shared by the sender and the receiver. By using the atom–cavity-field interaction and introducing an additional atom, we can teleport the two-atom entangled state successfully with a probability of 1.0. Moreover, we show that the scheme is insensitive to cavity decay and thermal field.

TELEPORTATION OF ANY FORM OF SINGLE-MODE QUANTUM STATES

By using the two-mode Einstein–Podolsky–Rosen (EPR) pair eigenstates or the two-mode squeezed vacuum as quantum channel we study the quantum teleportation of any form of single-mode quantum states (which include discrete and continuous variable quantum states). The elegant properties of the EPR pair eigenstates bring much convenience to our discussion.

Proposal of many-party controlled teleportation for multi-qubit entangled W state

A scheme of M-party controlled teleportation for one N-qubit entangled W state via (N-1) Einstein–Podolsky–Rosen (EPR) pairs and one (M+2)-qubit Greenberger–Horne–Zeilinger (GHZ) state is proposed. We achieve the teleportation in such a way that M agents can execute the Hadamard transformation, perform the measurement on their qubits and inform the receiver of their measurements. Then we discuss that the receiver cannot fully recover the state from the sender if one agent does not co-operate with him.

Teleportation of Any Form of Two-Mode Quantum States

By using two two-mode Einstein–Podolsky–Rosen (EPR) pair eigenstates or two two-mode squeezed states as quantum channels we study the quantum teleportation of any form of two-mode quantum states, which conclude discrete and continuous variable quantum states.

EFFICIENT QUANTUM KEY DISTRIBUTION SCHEME USING THE BELL STATE MEASUREMENT

In this paper we provide a quantum key distribution (QKD) scheme based on the correlations of Einstein–Podolsky–Rosen (EPR) pairs. The scheme uses an auxiliary qubit to interact with the EPR pair and does the Bell state measurement to get the key. It is proved to be secure. All EPR pairs are used in distributing the key except some error-checking bits. So it is efficient. On the other hand there are less classical communications needed in the scheme.

Creation of nonlocal spin-entangled electrons via Andreev tunneling, Coulomb blockade, and resonant transport

We discuss several scenarios for the creation of nonlocal spin-entangled electrons which provide a source of electronic Einstein–Podolsky–Rosen (EPR) pairs. Such EPR pairs can be used to test nonlocality of electrons in solid state systems, and they form the basic resources for quantum information processing. The central idea is to exploit the spin correlations naturally present in superconductors in form of Cooper pairs possessing spin-singlet wavefunctions. We show that nonlocal spin-entanglement in form of an effective Heisenberg spin interaction is induced between electron spins residing on two quantum dots with no direct coupling between them, but each of them being tunnel-coupled to the same superconductor. We then discuss a nonequilibrium setup with an applied bias where mobile and nonlocal spin-entanglement can be created by coherent injection of two electrons, in a pair (Andreev) tunneling process, into two spatially separated quantum dots and subsequently into two Fermi liquid leads. The current for injecting two spin-entangled electrons into different leads shows a resonance and allows the injection of electrons at the same orbital energy, which is a crucial requirement for the detection of spin-entanglement via the current noise. On the other hand, tunneling via the same dot into the same lead is suppressed by the Coulomb blockade effect of the quantum dots. We discuss Aharonov–Bohm oscillations in the current and show that they contain h/e and h/2e periods, which provides an experimental means to test the nonlocality of the entangled pair. Finally, we discuss a structure consisting of a superconductor weakly coupled to two separate one-dimensional leads with Luttinger liquid properties. We show that strong correlations again suppress the coherent subsequent tunneling of two electrons into the same lead, thus generating again nonlocal spin-entangled electrons in the Luttinger liquid leads.