Authors:V. G. Bagrov, D. M. Gitman, A. D. Levin, M. S. Meireles Abstract: International Journal of Quantum Information, Ahead of Print. Recently, an implementation of a universal set of one- and two-quantum-bit gates for quantum computation using spin states of coupled single-electron quantum dots was proposed. It was demonstrated that it is possible to execute a coherent control of a quantum system based on two-electron spin states in a double quantum dot, allowing state preparation, coherent manipulation, and projective readout. This possibility is based on rapid electrical control of the spin exchange interaction. These results motivated us to develop a formal theoretical study of the corresponding model of two coupled spins placed in a magnetic field and subjected to a time-dependent mutual Heisenberg interaction. Using possible exact solutions of the corresponding quantum problem, we study entangling of different separable initial states in this model. It is demonstrated that the entanglement due to a time-dependent Heisenberg interaction is dominating in comparison with the entanglement due to the action of an external magnetic field. Citation: International Journal of Quantum Information PubDate: 2017-01-05T06:02:50Z DOI: 10.1142/S021974991750006X

Authors:Masakazu Yoshida, Toru Kuriyama, Jun Cheng Abstract: International Journal of Quantum Information, Volume 14, Issue 08, December 2016. Mean king’s problem is a kind of quantum state discrimination problems. In the problem, we try to discriminate eigenstates of noncommutative observables with the help of classical delayed information. The problem has been investigated from the viewpoint of error detection and correction. We construct higher-dimensional quantum error-correcting codes against error corresponding to the noncommutative observables. Any code state of the codes provides a way to discriminate the eigenstates correctly with the classical delayed information. Citation: International Journal of Quantum Information PubDate: 2016-12-27T08:17:52Z DOI: 10.1142/S0219749916500489

Authors:Divya Taneja, Manish Gupta, Rajesh Narula, Jaskaran Bhullar Abstract: International Journal of Quantum Information, Ahead of Print. Obtaining quantum maximum distance separable (MDS) codes from dual containing classical constacyclic codes using Hermitian construction have paved a path to undertake the challenges related to such constructions. Using the same technique, some new parameters of quantum MDS codes have been constructed here. One set of parameters obtained in this paper has achieved much larger distance than work done earlier. The remaining constructed parameters of quantum MDS codes have large minimum distance and were not explored yet. Citation: International Journal of Quantum Information PubDate: 2016-12-29T08:32:51Z DOI: 10.1142/S0219749917500083

Authors:Milad Nanvakenari, Monireh Houshmand Abstract: International Journal of Quantum Information, Ahead of Print. In this paper, a three-party controlled quantum secure direct communication and authentication (QSDCA) protocol is proposed by using four particle cluster states via a quantum one-time pad and local unitary operations. In the present scheme, only under the permission of the controller, the sender and the receiver can implement secure direct communication successfully. But under any circumstances, Charlie cannot obtain the secret message. Eavesdropping detection and identity authentication are achieved with the help of the previously shared reusable base identity strings of users. This protocol is unconditionally secure in both ideal and practical noisy cases. In one transmission, a qubit of each four particle cluster state is used as controller’s permission and the same qubit with another qubit are used to recover two classical bits of information. In the proposed scheme, the efficiency is improved compared with the previous works. Citation: International Journal of Quantum Information PubDate: 2016-12-29T08:32:48Z DOI: 10.1142/S0219749917500022

Authors:Feng Liu Abstract: International Journal of Quantum Information, Ahead of Print. For any [math]-partite state [math], we define its quantum mutual information matrix as an [math][math][math][math][math] matrix whose [math]-entry is given by quantum mutual information [math]. Although each entry of quantum mutual information matrix, like its classical counterpart, is also used to measure bipartite correlations, the similarity ends here: quantum mutual information matrices are not always positive semidefinite even for collections of up to 3-partite states. In this work, we define the genuine n-partite mutual information which can be easily calculated. This definition is symmetric, nonnegative, bounded and more accurate for measuring multipartite states. Citation: International Journal of Quantum Information PubDate: 2016-12-16T07:37:54Z DOI: 10.1142/S0219749917500058

Authors:Kishore Thapliyal, Rishi Dutt Sharma, Anirban Pathak Abstract: International Journal of Quantum Information, Ahead of Print. Two new protocols for quantum binary voting are proposed. One of the proposed protocols is designed using a standard scheme for controlled deterministic secure quantum communication (CDSQC), and the other one is designed using the idea of quantum cryptographic switch, which uses a technique known as permutation of particles. A few possible alternative approaches to accomplish the same task (quantum binary voting) have also been discussed. Security of the proposed protocols is analyzed. Further, the efficiencies of the proposed protocols are computed, and are compared with that of the existing protocols. The comparison has established that the proposed protocols are more efficient than the existing protocols. Citation: International Journal of Quantum Information PubDate: 2016-12-16T07:37:54Z DOI: 10.1142/S0219749917500071

Authors:L. Jebli, B. Benzimoune, M. Daoud Abstract: International Journal of Quantum Information, Ahead of Print. A special emphasis is devoted to the concept of local quantum uncertainty as an indicator of quantum correlations. We study quantum discord for a class of two-qubit states parametrized by two parameters. Quantum discord based on local quantum uncertainty, von Neumann entropy and trace distance (Schatten 1-norm) are explicitly derived and compared. The behavior of quantum correlations, quantified via local quantum uncertainty, under decoherence effects is investigated. We show that the discordlike local quantum uncertainty exhibits the possibility of freezing behavior during its evolution. Citation: International Journal of Quantum Information PubDate: 2016-12-16T07:37:52Z DOI: 10.1142/S0219749917500010

Authors:Hailin Xiao, Ju Ni, Wu Xie, Shan Ouyang Abstract: International Journal of Quantum Information, Ahead of Print. As in classical coding theory, turbo product codes (TPCs) through serially concatenated block codes can achieve approximatively Shannon capacity limit and have low decoding complexity. However, special requirements in the quantum setting severely limit the structures of turbo product codes (QTPCs). To design a good structure for QTPCs, we present a new construction of QTPCs with the interleaved serial concatenation of [math]-type quantum convolutional codes (QCCs). First, [math]-type QCCs are proposed by exploiting the theory of CSS-type quantum stabilizer codes and QCCs, and the description and the analysis of encoder circuit are greatly simplified in the form of Hadamard gates and C-NOT gates. Second, the interleaved coded matrix of QTPCs is derived by quantum permutation SWAP gate definition. Finally, we prove the corresponding relation on the minimum Hamming distance of QTPCs associated with classical TPCs, and describe the state diagram of encoder and decoder of QTPCs that have a highly regular structure and simple design idea. Citation: International Journal of Quantum Information PubDate: 2016-12-16T07:37:52Z DOI: 10.1142/S0219749917500034

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: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