Authors:Toshiyuki Fujii, Shigemasa Matsuo, Noriyuki Hatakenaka Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. We propose a fluxon-controlled quantum computer incorporated with three-qubit quantum error correction using special gate operations, i.e. joint-phase and SWAP gate operations, inherent in capacitively coupled superconducting flux qubits. The proposed quantum computer acts exactly like a knitting machine at home. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:51Z DOI: 10.1142/S0219749916500404

Authors:Babatunde James Falaye, Guo-Hua Sun, Oscar Camacho-Nieto, Shi-Hai Dong Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. We present a scheme for joint remote state preparation (JRSP) of three-particle state via three tripartite Greenberger–Horne–Zeilinger (GHZ) entangled states as the quantum channel linking the parties. We use eight-qubit mutually orthogonal basis vector as measurement point of departure. The likelihood of success for this scheme has been found to be [math]. However, by putting some special cases into consideration, the chances can be ameliorated to [math] and 1. The effects of amplitude-damping noise, phase-damping noise and depolarizing noise on this scheme have been scrutinized and the analytical derivations of fidelities for the quantum noisy channels have been presented. We found that for [math], the states conveyed through depolarizing channel lose more information than phase-damping channel while the information loss through amplitude damping channel is most minimal. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:49Z DOI: 10.1142/S0219749916500349

Authors:Mazhar Ali Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. We investigate the possibility to restore genuine tripartite entanglement under local amplitude damping. We show that it is possible to protect genuine entanglement using CNOT and Hadamard gates. We analyze several ordering of such recovery operations. We find that for recovery operations applied after exposing qubits to decoherence, there is no enhancement in lifetime of genuine entanglement. Actual retrieval of entanglement is only possible when reversal scheme is applied before and after the decoherence process. We find that retrieval of entanglement for mixture of [math] state with white noise is more evident than the respective mixture of [math] state. We also find the retrieval of entanglement for similar mixture of [math] state as well. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:46Z DOI: 10.1142/S0219749916500398

Authors:J. Batle, M. Abutalib, S. Abdalla, Ahmed Farouk Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. The transmission of pure and mixed states along a quantum spin chain is investigated. Nonlocality between two qubits will evolve as it is transmitted through the quantum channel in a way that may violate or not the Clauser–Horne–Shimony–Holt (CHSH) Bell inequality at different times. This violation of local realism is analogue to the so-called sudden death and sudden birth features of entanglement. In the quantum channel, which will turn to be a damping one, some (mixed) states will be preferred according to the nature of the quantum correlations that are preserved during the evolution along the spin chain. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:44Z DOI: 10.1142/S0219749916500374

Authors:Xiling Xue, Hanwu Chen, Zhihao Liu Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. The search for structural anomalies in a complete graph, [math], using scattering quantum walks (SQWs) is investigated in this study. A complete graph with a second graph, [math], attached to one of its vertices is referred to as external structural anomaly. The structural change within a complete graph is called internal structural anomaly. First, an example with [math] being a triangle is presented to illustrate the problem. Then, a general proof is provided to show that the vertex to which [math] is attached can be found in [math] time steps as long as the connectivity between [math] and [math] is far less than [math]. Finally, two types of internal structural anomalies, namely, a complete graph with a missing edge and that with an extra loop, are considered. These two anomalies can be solved in a similar manner as external anomalies in [math] time steps. These examples demonstrate that Cottrell’s formalism in star graphs can be applied more generally. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:35Z DOI: 10.1142/S0219749916500350

Authors:Ying Shi, Li Zheng, Yu-Jie Liu, Chong Li Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. We investigate a remote establishment of entanglement sharing resource through entanglement transferred from continuous variables to discrete variables. The analysis of generation of entanglement for two initially unentangled atoms with different fields are performed and simultaneous observations of the max entanglement acquirement is given. Based on our result, we suppose that the max and stable entanglement acquirement can be obtained with appropriate field parameters. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:33Z DOI: 10.1142/S0219749916500386

Authors:Suzhen Yuan, Xia Mao, Lijiang Chen, Xiaofa Wang Abstract: International Journal of Quantum Information, Volume 14, Issue 07, October 2016. To reduce the time complexity of quantum morphology operations, two kinds of improved quantum dilation and erosion operations are proposed. Quantum parallelism is well used in the design of these operations. Consequently, the time complexity is greatly reduced compared with the previous quantum dilation and erosion operations. The neighborhood information of each pixel is needed in the process of designing quantum dilation and erosion operations. In order to get the neighborhood information, quantum position shifting transformation is utilized, which can make the neighborhood information store in a quantum image set. In this image set, the neighborhood information of pixel at location ([math], [math]) is stored at the same location ([math], [math]) of other images in the image set. All the pixels will be processed simultaneously, which is the performance of quantum parallelism. The time complexity analysis shows that these quantum operations have polynomial-time complexity which is much lower than the exponential-time complexity of the previous version. Citation: International Journal of Quantum Information PubDate: 2016-11-08T09:26:27Z DOI: 10.1142/S0219749916500362

Authors:Jin-Zhong Lin Abstract: International Journal of Quantum Information, Ahead of Print. By controlling the parameters of the system, the effective interaction between different atoms is achieved in different cavities. Based on the interaction, scheme to generate three-atom Greenberger–Horne–Zeilinger (GHZ) is proposed in coupled cavities. Spontaneous emission of excited states and decay of cavity modes can be suppressed efficiently. In addition, the scheme is robust against the variation of hopping rate between cavities. Citation: International Journal of Quantum Information PubDate: 2016-12-05T07:17:13Z DOI: 10.1142/S0219749917500046

Authors:Janusz Czub, Ryszard Veynar, Wiesław Laskowski, Marcin Pawłowski Abstract: International Journal of Quantum Information, Ahead of Print. In a typical, entanglement-based quantum key distribution (QKD) protocols the maximally entangled, singlet states are used. The standard way to generate them is to use parametric down conversion with low intensity laser beams. This way the probability to produce two or more entangled pairs is negligible. However, one obtains it at a cost of a large likelihood of producing no particles at all. In this work, we ask the question if this approach is the optimal one from the point of view of key generation rate. For a case study, we take BBM 92 protocol and find the optimal intensity of the beam. We show optimal intensities are much higher than the ones typically used. Our results can be generalized to other protocols based on singlet states. Citation: International Journal of Quantum Information PubDate: 2016-11-25T09:09:34Z DOI: 10.1142/S0219749916500490

Authors:Ze-Song Shen, Fang-Yu Hong Abstract: International Journal of Quantum Information, Ahead of Print. We present a new scheme for quantum interfaces (QIs) to accomplish the interconversion of photonic qubits and spin qubits based on optomechanical resonators and the spin–orbit-induced interactions in suspended carbon nanotube quantum dots (CNTQDs). This interface implements quantum spin transducers and further enables electrical manipulation of local electron spin qubits, which lays the foundation for all-electrical control of state transfer protocols between two distant quantum nodes in a quantum network. We numerically evaluate the state transfer processes and proceed to estimate the effect of each coupling strength on the operation fidelities. The simulation suggests that high operation fidelities are obtainable under realistic experimental conditions. Citation: International Journal of Quantum Information PubDate: 2016-11-23T06:04:38Z DOI: 10.1142/S0219749916500477

Authors:Guoqing Zhang, Xiuxiu Gao, Lina Liu Abstract: International Journal of Quantum Information, Ahead of Print. Influences of signal processing methods on photon number resolving capability of multi-pixel photon counter (MPPC) were studied in this work. Results show that the photon number resolving (PNR) capability of MPPC can be greatly improved by waveform integration of the avalanche pulses of MPPC, relative to the histograms of the output pulse amplitudes. Up to 47 photon-equivalent peaks can be distinguished in the PNR spectrum with pulsed light repetition frequency of 80[math]MHz and 5[math]ns time gate. The analog to digital converter (ADC) in oscilloscope with more bit resolution may be beneficial for the PNR of MPPC. Citation: International Journal of Quantum Information PubDate: 2016-11-23T06:04:36Z DOI: 10.1142/S0219749916500465

Authors:Y. Ben-Aryeh, A. Mann Abstract: International Journal of Quantum Information, Ahead of Print. Hilbert–Schmidt (HS) decompositions and Frobenius norms are used to analyze biseparability of 3-qubit systems, with particular emphasis on density matrices with maximally disordered subsystems (MDS) and on the [math] state mixed with white noise. The biseparable form of a MDS density matrix is obtained by using the Bell states of a 2-qubit subsystem, multiplied by density matrices of the third qubit, which include the relevant HS parameters. Using our methods, a sufficient condition and explicit biseparability of the [math] state mixed with white noise are given. They are compared with the sufficient condition for explicit full separability given in a previous work. Citation: International Journal of Quantum Information PubDate: 2016-11-23T06:04:33Z DOI: 10.1142/S0219749916500441

Authors:Dong-Sheng Wang Abstract: International Journal of Quantum Information, Ahead of Print. Quantum channels, which are completely positive and trace preserving mappings, can alter the dimension of a system, e.g. a quantum channel from a qubit to a qutrit. We study the convex set properties of dimension-altering quantum channels, and particularly the channel decomposition problem in terms of convex sum of extreme channels. We provide various quantum circuit representations of extreme and generalized extreme channels, which can be employed in an optimization to approximately decompose an arbitrary channel. Numerical simulations of low-dimensional channels are performed to demonstrate our channel decomposition scheme. Citation: International Journal of Quantum Information PubDate: 2016-11-17T08:43:38Z DOI: 10.1142/S0219749916500453

Authors:Paul B. Slater Abstract: International Journal of Quantum Information, Ahead of Print. We detect a certain pattern of behavior of separability probabilities [math] for two-qubit systems endowed with Hilbert–Schmidt (HS), and more generally, random induced measures, where [math] and [math] are the Bloch radii ([math]) of the qubit reduced states ([math]). We observe a relative repulsion of radii effect, that is [math], except for rather narrow “crossover” intervals [math]. Among the seven specific cases we study are, firstly, the “toy” seven-dimensional [math]-states model and, then, the fifteen-dimensional two-qubit states obtained by tracing over the pure states in [math]-dimensions, for [math], with [math] corresponding to HS (flat/Euclidean) measure. We also examine the real (two-rebit) [math], the [math]-states [math], and Bures (minimal monotone)–for which no nontrivial crossover behavior is observed–instances. In the two [math]-states cases, we derive analytical results; for [math], we propose formulas that well-fit our numerical results; and for the other scenarios, rely presently upon large numerical analyses. The separability probability crossover regions found expand in length (lower [math]) as [math] increases. This report continues our efforts [P. B. Slater, arXiv:1506.08739] to extend the recent work of [S. Milz and W. T. Strunz, J. Phys. A 48 (2015) 035306.] from a univariate ([math]) framework — in which they found separability probabilities to hold constant with [math] — to a bivariate ([math]) one. We also analyze the two-qutrit and qubit–qutrit counterparts reported in Quantum Inform. Process. 15 (2016) 3745 in this context, and study two-qubit separability probabilities of the form [math]. A physics.stack.exchange link to a contribution by Mark Fischler addressing, in considerable detail, the construction of suitable bivariate distributions is indicated at the end of the paper. Citation: International Journal of Quantum Information PubDate: 2016-11-15T06:19:31Z DOI: 10.1142/S0219749916500428

Authors:Jiarui Cai, Ziwen Pan, Tie-Jun Wang, Sihai Wang, Chuan Wang Abstract: International Journal of Quantum Information, Ahead of Print. Hyper-entanglement is a system constituted by photons entangled in multiple degrees of freedom (DOF), being considered as a promising way of increasing channel capacity and guaranteeing powerful eavesdropping safeguard. In this work, we propose a coding scheme based on a 3-particle hyper-entanglement of polarization and orbital angular momentum (OAM) system and its application as a quantum secure direct communication (QSDC) protocol. The OAM values are specially encoded by Fibonacci sequence and the polarization carries information by defined unitary operations. The internal relations of the secret message enhances security due to principle of quantum mechanics and Fibonacci sequence. We also discuss the coding capacity and security property along with some simulation results to show its superiority and extensibility. Citation: International Journal of Quantum Information PubDate: 2016-11-15T06:19:29Z DOI: 10.1142/S021974991650043X

Authors:F. L. Chen, Z. F. Han Abstract: International Journal of Quantum Information, Ahead of Print. Group signature scheme is a method of allowing a member of a group to sign a message anonymously on behalf of the group. The group administrator is in charge of adding group members and has the ability to reveal the original signer in the event of disputes. Based on controlled quantum teleportation with three-particle entangled W states, we propose a new quantum group signature scheme with designated receiver. Security analysis proves that the proposed scheme possesses the characteristics of group signature and resists the usual attacks. Compared with previous proposed schemes, this scheme follows security definition of group signature fully and meets its basic requirements. Citation: International Journal of Quantum Information PubDate: 2016-11-04T03:15:41Z DOI: 10.1142/S0219749916500416

Authors:Haozhen Situ, Zhiming Huang, Cai Zhang Abstract: International Journal of Quantum Information, Ahead of Print. Noise effects can be harmful to quantum information systems. In the present paper, we study noise effects in the context of quantum games with incomplete information, which have more complicated structure than quantum games with complete information. The effects of several paradigmatic noises on three newly proposed conflicting interest quantum games with incomplete information are studied using numerical optimization method. Intuitively noises will bring down the payoffs. However, we find that in some situations the outcome of the games under the influence of noise effects are counter-intuitive. Sometimes stronger noise may lead to higher payoffs. Some properties of the game, like quantum advantage, fairness and equilibrium, are invulnerable to some kinds of noises. Citation: International Journal of Quantum Information PubDate: 2016-09-21T07:49:12Z DOI: 10.1142/S0219749916500337

Authors:Carlos A. González-Gutiérrez, Ricardo Román-Ancheyta, Diego Espitia, Rosario Lo Franco Abstract: International Journal of Quantum Information, Ahead of Print. Knowledge of the relationships among different features of quantumness, like entanglement and state purity, is important from both fundamental and practical viewpoints. Yet, this issue remains little explored in dynamical contexts for open quantum systems. We address this problem by studying the dynamics of entanglement and purity for two-qubit systems using paradigmatic models of radiation-matter interaction, with a qubit being isolated from the environment (spectator configuration). We show the effects of the corresponding local quantum channels on an initial two-qubit pure entangled state in the concurrence–purity diagram and find the conditions which enable dynamical closed formulas of concurrence, used to quantify entanglement, as a function of purity. We finally discuss the usefulness of these relations in assessing entanglement and purity thresholds which allow noisy quantum teleportation. Our results provide new insights about how different properties of composite open quantum systems behave and relate each other during quantum evolutions. Citation: International Journal of Quantum Information PubDate: 2016-09-19T07:36:41Z DOI: 10.1142/S0219749916500313

Authors:Apoorva Patel, Anjani Priyadarsini Abstract: International Journal of Quantum Information, Ahead of Print. Given a quantum Hamiltonian and its evolution time, the corresponding unitary evolution operator can be constructed in many different ways, corresponding to different trajectories between the desired end-points and different series expansions. A choice among these possibilities can then be made to obtain the best computational complexity and control over errors. It is shown how a construction based on Grover’s algorithm scales linearly in time and logarithmically in the error bound, and is exponentially superior in error complexity to the scheme based on the straightforward application of the Lie–Trotter formula. The strategy is then extended first to simulation of any Hamiltonian that is a linear combination of two projection operators, and then to any local efficiently computable Hamiltonian. The key feature is to construct an evolution in terms of the largest possible steps instead of taking small time steps. Reflection operations and Chebyshev expansions are used to efficiently control the total error on the overall evolution, without worrying about discretization errors for individual steps. We also use a digital implementation of quantum states that makes linear algebra operations rather simple to perform. Citation: International Journal of Quantum Information PubDate: 2016-09-14T01:52:34Z DOI: 10.1142/S0219749916500271

Authors:Francesco Albarelli, Tommaso Guaita, Matteo G. A. Paris Abstract: International Journal of Quantum Information, Ahead of Print. The quantum backflow effect is a counterintuitive behavior of the probability current of a free particle, which may be negative even for states with vanishing negative momentum component. Here, we address the notion of nonclassicality arising from the backflow effect, i.e. from the negativity of the probability current, and analyze its relationships with the notion of nonclassicality based on the negativity of the Wigner function. Our results show that backflow is linked to a different, and in fact more restrictive, notion of nonclassicality, the negativity of the Wigner function being only a necessary prerequisite for its occurrence. This hierarchical structure may be confirmed by looking at the addition of thermal noise, which more easily destroys the negativity of the probability current than the negativity of the Wigner function itself. Citation: International Journal of Quantum Information PubDate: 2016-09-14T01:52:10Z DOI: 10.1142/S0219749916500325