Quantum teleportation with partially entangled states via noisy channels

Using a partially entangled EPR-type state as quantum channel, we investigate quantum teleportation (QT) of a qubit state in noisy environments by solving the master equation in the Lindblad form. We analyze the different influence for the partially entangled EPR-type channel and the EPR channel on the fidelity and the average fidelity of the QT process in the presence of Pauli noises. It is found that the fidelity depends on the type and the strength of the noise, and the initial state to be teleported. Moreover, the EPR channel is more robust than the partially entangled EPR-type channel against the influence of the noises. It is also found that the partially entangled EPR-type channel enables the average fidelity as a function of the decoherence parameter $kt$ to decay with different velocities for different Pauli noises.     

Bidirectional teleportation of a pure EPR state by using GHZ states

In the present paper, a novel bidirectional quantum teleportation protocol is proposed. By using entanglement swapping technique, two GHZ states are shared as a quantum channel between Alice and Bob as legitimate users. In this scheme, based on controlled-not operation, single-qubit measurement, and appropriate unitary operations, two users can simultaneously transmit a pure EPR state to each other, While, in the previous protocols, the users can just teleport a single-qubit state to each other via more than four-qubit state. Therefore, the proposed scheme is economical compared with previous protocols.     

Quantum network dialogue protocol based on continuous-variable GHZ states

Quantum dialogue network, as a considerable topic, promotes high efficiency and instantaneousness in quantum communication through simultaneously deducing the secret information over the quantum channel. A new quantum network dialogue protocol is proposed based on continuous-variable GHZ states. In the protocol, the quantum dialogue could be conducted simultaneously among multiple legitimate communication parties. The security of the proposed protocol is ensured by the correlation of continuous-variable GHZ entangled states and the decoy states inserted into the GHZ states in the randomly selected time slots. In addition, the proposed quantum network dialogue protocol with continuous-variable quantum states improves the communication efficiency with the perfect utilization of quantum bits greatly.     

Fault tolerant deterministic quantum communications using GHZ states over collective-noise channels

This study proposes two new coding functions for a GHZ state and a GHZ-like state, respectively. Based on these coding functions, two fault tolerant deterministic quantum communication (DQC) protocols are proposed. Each of the new DQC’s is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. The sender can use the proposed coding functions to encode his/her message, and the receiver can perform the Bell measurement to obtain the sender’s message. In comparison to the existing fault tolerant DQC protocols over collective-noise channels, the proposed protocols provide the best qubit efficiency. Moreover, the proposed protocols are also free from the ordinary eavesdropping and the information leakage.     

Quantum teleportation and superdense coding through the composite W-Bell channel

The states of triqubit systems have an important category W states. A class of asymmetric W states |W _n 〉₁₂₃ were proposed by Agrawal and Pati (Phys Rev A 74:062320, 2006). We introduce an entangled system composed of the |W _n 〉₁₂₃ states and Bell pairs and show its utility for perfect teleportation and superdense coding.     

Biseparability of noisy pseudopure,W and GHZ states using conditional quantum relative Tsallis entropy

We employ the conditional version of sandwiched Tsallis relative entropy to determine \(1:N-1\) separability range in the noisy one-parameter families of pseudopure and Werner-like N-qubit W, GHZ states. The range of the noisy parameter, for which the conditional sandwiched Tsallis relative entropy is positive, reveals perfect agreement with the necessary and sufficient criteria for separability in the \(1:N-1\) partition of these one parameter noisy states.     

A revisit to non-maximally entangled mixed states: teleportation witness,noisy channel and discord

We constructed a class of non-maximally entangled mixed states (Adhikari et al. in Quantum Inf Comput 10:0398, 2010) and extensively studied their entanglement properties and also their usefulness as teleportation channels. In this article, we have revisited our constructed state and have studied it from three different perspectives. Since every entangled state is associated with a witness operator, we have found a suitable entanglement as well as teleportation witness operator for our non-maximally entangled mixed states. We considered the noisy channel’s effects on our constructed states to see how much it affects the states’ capacities as teleportation channels. For this purpose, we have mainly focussed on amplitude damping channel. A comparative study on concurrence and quantum discord of our constructed state of Adhikari et al. (2010) has also been carried out here.     

π-calculus with noisy channels

It is assumed in the π-calculus that communication channels are always noiseless. But it is usually not the case in the mobile systems that developers are faced with in the real life. In this paper, we introduce an extension of π, called π_N, in which noisy channels may be present. A probabilistic transitional semantics of π_N is given. The notions of approximate (strong) bisimilarity and equivalence between agents in π_N are proposed, and various algebraic laws for them are established. In particular, we introduce the notion of stratified bisimulation which is suited to describe behavior equivalence between infinite probabilistic processes. Some useful techniques for reasoning about approximate bisimilarity and equivalence are developed. We also introduce a notion of reliability in order to compare different behaviors of an agent in π and π_N. It is shown that reliability is preserved by the basic combinators in π. A link between reliability and bisimulation is given. This provides us with a uniform framework in which we can reason about both correctness properties and reliability of mobile systems. Also, a potential way of combing value-passing process algebras and Shannon’s information theory is pointed out.     

Generation of GHZ states with invariant-based shortcuts

A scheme is proposed to generate three-atom GHZ states by applying the inversely engineered control method on the basis of Lewis–Riesenfeld invariants. In the proposal, three atoms that have different configurations are trapped in a bimodal cavity. Numerical simulations indicate that our protocol has an obvious improvement of speed for the generation of GHZ states. Moreover, the present scheme is robust against both parameter fluctuations and dissipation.     

An efficient scheme for multi-party quantum state sharing of an arbitrary multi-qubit state with one GHZ channel

We present an innovative and extremely efficient scheme to share an arbitrary multi-qubit state between n agents with only 1 GHZ channel under control of m agents in a network. Compared with existing ones in this literature, our scheme requires less communication resources, least qubits and only three physical favorable simple operations (single-qubit measurement, Bell-basis measurement and CNOT gate operations) are included, leading to a higher overall efficiency.     

Fault tolerant quantum key distributions using entanglement swapping of GHZ states over collective-noise channels

This work proposes two fault tolerant quantum key distribution (QKD) protocols. Each of which is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. Due to the use of the entanglement swapping of Greenberger–Horne–Zeilinger (GHZ) state as well as the decoy logical qubits, the new protocols provide the best qubit efficiency among the existing fault tolerant QKD protocols over the same collective-noise channel. The receiver simply performs two Bell measurements to obtain the raw key. Moreover, the proposed protocols are free from several well-known attacks and can also be secure over a lossy channel.     

Deterministic remote preparation of arbitrary multi-qubit equatorial states via two-qubit entangled states

We propose an efficient scheme for remotely preparing an arbitrary n-qubit equatorial state via n two-qubit maximally entangled states. Compared to the former scheme (Wei et al. in Quantum Inf Process 16:260, 2017) that has the 50% successful probability when the amplitude factors of prepared states are \(2^{-n{/}2}\), the probability would be increased to 100% by using of our modified proposal. The feasibility of our scheme for remote preparation arbitrary multi-qubit equatorial states is explicitly demonstrated by theoretical studies and concrete examples.     

Quantum teleportation in a dissipative environment

We investigate quantum teleportation of a single-qubit state for the situation in which both qubits of the entangled channel are subjected to local structured reservoirs. We consider the effect of entanglement sudden death (ESD) of the channel on the average fidelity of the teleportation. It is shown the appearance of ESD leads to an abrupt variation of the fidelity of quantum teleportation. In addition, we show the fidelity exhibits oscillations in the non-Markovian reservoir due to the memory effect of the reservoir.     

Optimal remote preparation of arbitrary multi-qubit real-parameter states via two-qubit entangled states

In this paper, we present an efficient scheme for remote state preparation of arbitrary n-qubit states with real coefficients. Quantum channel is composed of n maximally two-qubit entangled states, and several appropriate mutually orthogonal bases including the real parameters of prepared states are delicately constructed without the introduction of auxiliary particles. It is noted that the successful probability is 100% by using our proposal under the condition that the parameters of prepared states are all real. Compared to general states, the probability of our protocol is improved at the cost of the information reduction in the transmitted state.     

Polar quantum channel coding with optical multi-qubit entangling gates for capacity-achieving channels

We demonstrate a fashion of quantum channel combining and splitting, called polar quantum channel coding, to generate a quantum bit (qubit) sequence that achieves the symmetric capacity for any given binary input discrete quantum channels. The present capacity is achievable subject to input of arbitrary qubits with equal probability. The polarizing quantum channels can be well-conditioned for quantum error-correction coding, which transmits partially quantum data through some channels at rate one with the symmetric capacity near one but at rate zero through others.     

Control over noisy channels

Communication is an important component of distributed and networked controls systems. In our companion paper, we presented a framework for studying control problems with a digital noiseless communication channel connecting the sensor to the controller. Here, we generalize that framework by applying traditional information theoretic tools of source coding and channel coding to the problem. We present a general necessary condition for observability and stabilizability for a large class of communication channels. Then, we study sufficiency conditions for Internet-like channels that suffer erasures.     

Bidirectional controlled teleportation by using nine-qubit entangled state in noisy environments

A theoretical scheme is proposed to implement bidirectional quantum controlled teleportation (BQCT) by using a nine-qubit entangled state as a quantum channel, where Alice may transmit an arbitrary two-qubit state called qubits \(A_1\) and \(A_2\) to Bob; and at the same time, Bob may also transmit an arbitrary two-qubit state called qubits \(B_1\) and \(B_2\) to Alice via the control of the supervisor Charlie. Based on our channel, we explicitly show how the bidirectional quantum controlled teleportation protocol works. And we show this bidirectional quantum controlled teleportation scheme may be determinate and secure. Taking the amplitude-damping noise and the phase-damping noise as typical noisy channels, we analytically derive the fidelities of the BQCT process and show that the fidelities in these two cases only depend on the amplitude parameter of the initial state and the decoherence noisy rate.     

Quantum teleportation of a generic two-photon state with weak cross-Kerr nonlinearities

We present a scheme for teleporting a generic two-photon polarization state by using two EPR states as quantum channel based on weak cross-Kerr nonlinearities. As the core component of the present framework, the quantum nondemolition detector based on the weak cross-Kerr nonlinearity acts as an EPR entangler as well as the Bell-state analyzer. This makes the teleportation protocol be achieved near deterministically and be feasible in the current experimental technology.     

Remote preparation of an arbitrary multi-qubit state via two-qubit entangled states

We propose a novel scheme for remote preparation of an arbitrary n-qubit state with the aid of an appropriate local \(2^n\times 2^n\) unitary operation and n maximally entangled two-qubit states. The analytical expression of local unitary operation, which is constructed in the form of iterative process, is presented for the preparation of n-qubit state in detail. We obtain the total successful probabilities of the scheme in the general and special cases, respectively. The feasibility of our scheme in preparing remotely multi-qubit states is explicitly demonstrated by theoretical studies and concrete examples, and our results show that the novel proposal could enlarge the applied range of remote state preparation.