Zhi-Guo Qu

Hyperentanglement concentration for n-photon 2n-qubit systems with linear optics

Hyperentanglement involves multiple degrees of freedom of a quantum system and has attracted a lot of attention recently because of its high efficiency in quantum applications. We propose some practical schemes using linear optics for partially entangled n-photon 2n-qubit systems with spatial and polarization degrees of freedom. The states involved are not equivalent to the general Bell states or GHz states under local quantum operations and classical communication. Our schemes are based on the parameter-splitting method, which can change different entanglement coefficients into equal coefficients. They are very efficient and practical as they use only linear-optical elements and do not require nonlinear optics.

Effect of noise on deterministic joint remote preparation of an arbitrary two-qubit state

Quantum communication has attracted much attention in recent years. Deterministic joint remote state preparation (DJRSP) is an important branch of quantum secure communication which could securely transmit a quantum state with 100% success probability. In this paper, we study DJRSP of an arbitrary two-qubit state in noisy environment. Taking a GHZ based DJRSP scheme of a two-qubit state as an example, we study how the scheme is influenced by all types of noise usually encountered in real-world implementations of quantum communication protocols, i.e., the bit-flip, phase-flip (phase-damping), depolarizing, and amplitude-damping noise. We demonstrate that there are four different output states in the amplitude-damping noise, while there is the same output state in each of the other three types of noise. The state-independent average fidelity is presented to measure the effect of noise, and it is shown that the depolarizing noise has the worst effect on the DJRSP scheme, while the amplitude-damping noise or the phase-flip has the slightest effect depending on the noise rate. Our results are also suitable for JRSP and RSP.

Deterministic remote preparation via the Brown state

We propose two deterministic remote state preparation (DRSP) schemes by using the Brown state as the entangled channel. Firstly, the remote preparation of an arbitrary two-qubit state is considered. It is worth mentioning that the construction of measurement bases plays a key role in our scheme. Then, the remote preparation of an arbitrary three-qubit state is investigated. The proposed schemes can be extended to controlled remote state preparation (CRSP) with unit success probabilities. At variance with the existing CRSP schemes via the Brown state, the derived schemes have no restriction on the coefficients, while the success probabilities can reach 100%. It means the success probabilities are greatly improved. Moreover, we pay attention to the DRSP in noisy environments under two important decoherence models, the amplitude-damping noise and phase-damping noise.

Effect of quantum noise on deterministic remote state preparation of an arbitrary two-particle state via various quantum entangled channels

As one of important research branches of quantum communication, deterministic remote state preparation (DRSP) plays a significant role in quantum network. Quantum noises are prevalent in quantum communication, and it can seriously affect the safety and reliability of quantum communication system. In this paper, we study the effect of quantum noise on deterministic remote state preparation of an arbitrary two-particle state via different quantum channels including the

Controlled bidirectional remote preparation of three-qubit state

\chi

Quantum Relief algorithm

χ state, Brown state and GHZ state. Firstly, the output states and fidelities of three DRSP algorithms via different quantum entangled channels in four noisy environments, including amplitude-damping, phase-damping, bit-flip and depolarizing noise, are presented, respectively. And then, the effects of noises on three kinds of preparation algorithms in the same noisy environment are discussed. In final, the theoretical analysis proves that the effect of noise in the process of quantum state preparation is only related to the noise type and the size of noise factor and independent of the different entangled quantum channels. Furthermore, another important conclusion is given that the effect of noise is also independent of how to distribute intermediate particles for implementing DRSP through quantum measurement during the concrete preparation process. These conclusions will be very helpful for improving the efficiency and safety of quantum communication in a noisy environment.

The effect of quantum noise on two different deterministic remote state preparation of an arbitrary three-particle state protocols

Quantum noise severely affects the security and reliability of quantum communication system. In this paper, we study the effect of quantum noise on quantum multiparty communication protocols. Taking a two-qubit joint remote state preparation (JRSP) scheme as an example, we point out that there are some calculation mistakes in a former JRSP scheme [X.W. Guan, X.B. Chen, L.C. Wang and Y.X. Yang, Int. J. Theor. Phys. 53(4) (2014) 2236.]. The revised output states and fidelities in two types of noise are presented, respectively. More importantly, we present a more general form for describing the effect of noise on multi-qubit system, which is fit for the case where different types of noise act on the system consecutively. The process of the JRSP scheme in two types of noise is discussed, respectively. It is shown that the noisy effect in the general case is much stronger than the former one for the most part. Our study will be helpful for analyzing the effect of quantum noise on quantum multiparty communication system.

A novel quantum image steganography algorithm based on exploiting modification direction

We present a novel scheme for controlled bidirectional remote state preparation by using thirteen-qubit entangled state as the quantum channel, where both Alice and Bob transfer an arbitrary three-qubit state to each other simultaneously via the control of Charlie. Firstly, in the ideal environment, we consider our scheme in two cases that the coefficients of prepared state are real and complex, respectively. The corresponding measurement bases are devised. Secondly, we discuss our scheme in four types of noisy environment (bit-flip, phase-flip, amplitude-damping and phase-damping noisy environments) and calculate the corresponding fidelities of the output state. Finally, the efficiency of our scheme is calculated and some discussions are given.