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 International Journal of Quantum Information   [SJR: 0.595]   [H-I: 22]   Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 0219-7499 - ISSN (Online) 1793-6918    Published by World Scientific  [120 journals]
• Parameter estimation of qubit states with unknown phase parameter
• Authors: Jun Suzuki
Abstract: International Journal of Quantum Information, Volume 13, Issue 01, February 2015. We discuss a problem of parameter estimation for quantum two-level system, qubit system, in presence of unknown phase parameter. We analyze trade-off relations for mean square errors (MSEs) when estimating relevant parameters with separable measurements based on known precision bounds; the symmetric logarithmic derivative (SLD) Cramér–Rao (CR) bound and Hayashi–Gill–Massar (HGM) bound. We investigate the optimal measurement which attains the HGM bound and discuss its properties. We show that the HGM bound for relevant parameters can be attained asymptotically by using some fraction of given n quantum states to estimate the phase parameter. We also discuss the Holevo bound which can be attained asymptotically by a collective measurement.
Citation: International Journal of Quantum Information
PubDate: Fri, 13 Mar 2015 08:03:11 GMT
DOI: 10.1142/S0219749914500440

• Quantum blind signature with an offline repository
• Authors: J. Ribeiro, A. Souto, P. Mateus
Abstract: International Journal of Quantum Information, Ahead of Print. We propose a quantum blind signature scheme that achieves perfect security under the assumption of an honest offline repository. The security of the protocol also relies on perfect private quantum channels, which are achievable using quantum one-time pads with keys shared via a quantum key distribution (QKD) protocol. The proposed approach ensures that signatures cannot be copied and that the sender must compromise to a single message, which are important advantages over classical protocols for certain applications.
Citation: International Journal of Quantum Information
PubDate: Fri, 24 Apr 2015 07:13:18 GMT
DOI: 10.1142/S0219749915500161

• Quantum stabilizer codes from Abelian and non-Abelian groups association
schemes
Abstract: International Journal of Quantum Information, Ahead of Print. A new method for the construction of the binary quantum stabilizer codes is provided, where the construction is based on Abelian and non-Abelian groups association schemes. The association schemes based on non-Abelian groups are constructed by bases for the regular representation from U6n, T4n, V8n and dihedral D2n groups. By using Abelian group association schemes followed by cyclic groups and non-Abelian group association schemes a list of binary stabilizer codes up to 40 qubits is given in tables 4, 5 and 10. Moreover, several binary stabilizer codes of minimum distances 5, 7 and 8 with good quantum parameters is presented. The preference of this method specially for Abelian group association schemes is that one can construct any binary quantum stabilizer code with any distance by using the commutative structure of association schemes.
Citation: International Journal of Quantum Information
PubDate: Fri, 24 Apr 2015 07:13:01 GMT
DOI: 10.1142/S0219749915500215

• Wigner rotation via Fermi–Walker transport and relativistic EPR
correlations in the Schwarzschild spacetime
• Authors: K. Bakke, C. Furtado, A. M. de M. Carvalho
Abstract: International Journal of Quantum Information, Ahead of Print. The Wigner rotation angle for a particle in a circular motion in the Schwarzschild spacetime is obtained via the Fermi–Walker transport of spinors. Then, by applying the Wentzel, Kramers, Brillouin (WKB) approximation, a possible application of the Fermi–Walker transport of spinors in relativistic Einstein–Podolsky–Rosen (EPR) correlations is discussed, where it is shown that the spins of the correlated particle undergo a precession in an analogous way to that obtained by Terashima and Ueda [H. Terashima and M. Ueda, Phys. Rev. A69, 032113 (2004)] via the application of successive infinitesimal Lorentz transformations. Moreover, from the WKB approach, it is also shown that the degree of violation of the Bell inequality depends on the Wigner rotation angle obtained via the Fermi–Walker transport. Finally, the relativistic effects from the geometry of the spacetime and the accelerated motion of the correlated particles is discussed in the nonrelativistic limit.
Citation: International Journal of Quantum Information
PubDate: Fri, 24 Apr 2015 07:12:51 GMT
DOI: 10.1142/S0219749915500203

• The one-way information deficit for a class of two-qubit states
• Authors: H. Eftekhari, E. Faizi
Abstract: International Journal of Quantum Information, Ahead of Print. So far, one-way information deficit (OWID) has been calculated explicitly only for Bell-diagonal states and the four-parameter family of X-states with additional assumptions and expressions for more general quantum states are not known. In this paper, we derive explicit expressions for OWID for a larger class of two-qubit states, namely, a five-parameter family of two-qubit states. The dynamic behavior of the OWID under decoherence channel is investigated and it is shown that the OWID is more robust against the decoherence than the entanglement.
Citation: International Journal of Quantum Information
PubDate: Tue, 21 Apr 2015 03:44:27 GMT
DOI: 10.1142/S0219749915500124

• Secure identity-based encryption in the quantum random oracle model
• Authors: Mark Zhandry
Abstract: International Journal of Quantum Information, Ahead of Print. We give the first proof of security for an identity-based encryption (IBE) scheme in the quantum random oracle model. This is the first proof of security for any scheme in this model that does not rely on the assumed existence of so-called quantum-secure pseudorandom functions (PRFs). Our techniques are quite general and we use them to obtain security proofs for two random oracle hierarchical IBE schemes and a random oracle signature scheme, all of which have previously resisted quantum security proofs, even assuming quantum-secure PRFs. We also explain how to remove quantum-secure PRFs from prior quantum random oracle model proofs. We accomplish these results by developing new tools for arguing that quantum algorithms cannot distinguish between two oracle distributions. Using a particular class of oracle distributions that we call semi-constant distributions, we argue that the aforementioned cryptosystems are secure against quantum adversaries.
Citation: International Journal of Quantum Information
PubDate: Tue, 21 Apr 2015 03:44:24 GMT
DOI: 10.1142/S0219749915500148

• Classical extension of quantum-correlated separable states
• Authors: G. Bellomo, A. Plastino, A. R. Plastino
Abstract: International Journal of Quantum Information, Ahead of Print. Li and Luo [Phys. Rev. A78 (2008) 024303] discovered a remarkable relation between discord and entanglement. It establishes that all separable states can be obtained via reduction of a classically-correlated state "living" in a space of larger dimension. Starting from this result, we discuss here an optimal classical extension of separable states and explore this notion for low-dimensional systems. We find that the larger the dimension of the classical extension, the larger the discord in the original separable state. Further, we analyze separable states of maximum discord in ℂ2 ⊗ ℂ2 and their associated classical extensions showing that, from the reduction of a classical state in (ℂ2 ⊗ ℂ3) ⊗ ℂ2, one can obtain a separable state of maximum discord in ℂ2 ⊗ ℂ2.
Citation: International Journal of Quantum Information
PubDate: Tue, 21 Apr 2015 03:44:24 GMT
DOI: 10.1142/S021974991550015X

• Generation of multi-photon entanglement
• Authors: Dong Xie, An Min Wang
Abstract: International Journal of Quantum Information, Ahead of Print. We propose a new scheme to generate multi-photon entanglement in two steps. First, we utilize a superconductor to create multi-quantum-dot entanglement; secondly, we use the input photon to transfer it into multi-photon entanglement. Moreover, the maximum probability for the swap of photon and quantum-dot qubits is close to unity for a single input Gaussian photon. More importantly, by mapping the multi-quantum-dot state into coherent states of oscillators, such as cavity modes, the multi-quantum-dot entanglement in our scheme can be protected from the decoherence induced by the noise. Thus, it is possible to generate more than eight spatially separated entangled photons in the realistic experimental conditions.
Citation: International Journal of Quantum Information
PubDate: Wed, 15 Apr 2015 05:14:33 GMT
DOI: 10.1142/S0219749915500185

• Three-party quantum summation without a trusted third party
• Authors: Cai Zhang, Zhi-Wei Sun, Xiang Huang, Dong-Yang Long
Abstract: International Journal of Quantum Information, Ahead of Print. In this paper, we propose a quantum summation protocol, in which the genuinely maximally entangled six-qubit states found by Borras et al., are employed. Because of the excellent properties of the genuinely maximally entangled six-qubit states, the presented protocol allows three participants to compute the summation of their inputs without the help of a trusted third party and preserve the privacy of their inputs, respectively. The participants do not need any unitary operations. In addition, the proposed protocol utilizes the one-step quantum transmission and therefore is congenitally free from Trojan horse attacks. We have also shown that our protocol is secure against other well-known attacks over lossy and noisy quantum channels.
Citation: International Journal of Quantum Information
PubDate: Thu, 02 Apr 2015 02:04:16 GMT
DOI: 10.1142/S0219749915500112

• Boson-sampling with non-interacting fermions
• Authors: V. S. Shchesnovich
Abstract: International Journal of Quantum Information, Ahead of Print. We explore the conditions under which identical particles in unitary linear networks behave as the other species, i.e. bosons as fermions and fermions as bosons. It is found that the Boson-sampling (BS) computer of Aaronson and Arkhipov can be implemented in an interference experiment with non-interacting fermions in an appropriately entangled state. Moreover, a scheme is proposed which simulates the scattershot version of the BS computer by preparing, on the fly, the required entangled state of fermions from an unentangled one.
Citation: International Journal of Quantum Information
PubDate: Thu, 02 Apr 2015 02:04:16 GMT
DOI: 10.1142/S0219749915500136

• High performance reconciliation for continuous-variable quantum key
distribution with LDPC code
• Authors: Dakai Lin, Duan Huang, Peng Huang, Jinye Peng, Guihua Zeng
Abstract: International Journal of Quantum Information, Ahead of Print. Reconciliation is a significant procedure in a continuous-variable quantum key distribution (CV-QKD) system. It is employed to extract secure secret key from the resulted string through quantum channel between two users. However, the efficiency and the speed of previous reconciliation algorithms are low. These problems limit the secure communication distance and the secure key rate of CV-QKD systems. In this paper, we proposed a high-speed reconciliation algorithm through employing a well-structured decoding scheme based on low density parity-check (LDPC) code. The complexity of the proposed algorithm is reduced obviously. By using a graphics processing unit (GPU) device, our method may reach a reconciliation speed of 25 Mb/s for a CV-QKD system, which is currently the highest level and paves the way to high-speed CV-QKD.
Citation: International Journal of Quantum Information
PubDate: Mon, 23 Mar 2015 11:21:00 GMT
DOI: 10.1142/S0219749915500100

• Implementation of a quantum $\sqrt{{\rm swap}}$ gate for two distant atoms
trapped in separate cavities
• Authors: Xiu Lin, Rong-Can Yang, Xiang Chen
Abstract: International Journal of Quantum Information, Ahead of Print. We present a scheme to implement a quantum $\sqrt{{\rm swap}}$ gate for two-atom trapped in distant cavities connected via an optical fiber. In the whole process, the atomic system, the cavity modes and the fiber are not excited ensuring that the operation is insensitive to atomic spontaneous emission, cavity decay and the fiber loss. This scheme is significant for distributed and scalable quantum computation.
Citation: International Journal of Quantum Information
PubDate: Fri, 27 Feb 2015 03:32:23 GMT
DOI: 10.1142/S0219749915500033

• Minimum remote state preparation of an arbitrary two-level one-atom state
via cavity QED
• Authors: Yahong Wang, Changshui Yu
Abstract: International Journal of Quantum Information, Ahead of Print. In this paper, we propose three schemes for remotely state preparation (RSP) an arbitrary two-level one-atom state via cavity quantum electro dynamics (QED) with minimal resources consumption. In the first case, a Greenberger–Horne–Zeilinger (GHZ) state is used as quantum channel; in the second case, the sender needs to construct an quantum channel with both of the assistant of cavity QED and the knowledge about the state to be remotely prepared. In each scheme, only 1 cbit and 1 ebit are needed with the aid of cavity QED. In the third case, we combine the first two protocols and give a theoretical proposal for controlled RSP with only 2 cbits and 1 ebit resources consumption.
Citation: International Journal of Quantum Information
PubDate: Fri, 27 Feb 2015 03:32:23 GMT
DOI: 10.1142/S0219749915500094

• Entanglement entropy in quasi-symmetric multi-qubit states
• Authors: Zhi-Hua Li, An-Min Wang
Abstract: International Journal of Quantum Information, Ahead of Print. We generalize the symmetric multi-qubit states to their q-analogs, whose basis vectors are identified with the q-Dicke states. We study the entanglement entropy in these states and find that entanglement is extruded towards certain regions of the system due to the inhomogeneity aroused by q-deformation. We also calculate entanglement entropy in ground states of a related q-deformed Lipkin–Meshkov–Glick (LMG) model and show that the singularities of entanglement can correctly signify the quantum phase transition points for different strengths of q-deformation.
Citation: International Journal of Quantum Information
PubDate: Wed, 25 Feb 2015 02:17:12 GMT
DOI: 10.1142/S0219749915500070

• An achievable rate for private classical information over a quantum
• Authors: Alireza Nadem Ghazvini, Seyed Vahab AL-Din Makki, Shahpoor Alirezaee
Abstract: International Journal of Quantum Information, Ahead of Print. The rate region for transmission of classical information over a quantum broadcast channel and an inner bound for the rate of transmission of private classical information over a single-user quantum channel have been achieved in the previous paper. In this work, we extended the proofs of them to obtain an achievable private classical capacity for a two receivers quantum broadcast channel.
Citation: International Journal of Quantum Information
PubDate: Wed, 25 Feb 2015 02:17:11 GMT
DOI: 10.1142/S0219749915500057

• Manipulation of the stationary entanglement of three atoms coupled to a
common environment
• Authors: Fang Su
Abstract: International Journal of Quantum Information, Ahead of Print. In this work, we study the dynamics of three entangled atoms coupled to a common structured reservoir. The atoms are initially prepared in different W-like states characterized by different relative phases. We examine the roles of initial relative phases on the energy transfers among the individual atoms as well as atomic entanglement dynamics. We show that the features of quantum interferences induced by initial relative phases greatly affect the energy transfers and entanglement dynamics. In particular, a suitable choice of initial phases can increase atomic stationary entanglement over their initial value. The results imply a possible control strategy for atomic entanglement dynamics.
Citation: International Journal of Quantum Information
PubDate: Tue, 24 Feb 2015 07:59:47 GMT
DOI: 10.1142/S0219749915500082

• The lower bound to the concurrence for four-qubit W state under noisy
channels
• Authors: Pakhshan Espoukeh, Pouria Pedram
Abstract: International Journal of Quantum Information, Ahead of Print. We study the dynamics of four-qubit W state under various noisy environments by solving analytically the master equation in the Lindblad form in which the Lindblad operators correspond to the Pauli matrices and describe the decoherence of states. Also, we investigate the dynamics of the entanglement using the lower bound to the concurrence. It is found that while the entanglement decreases monotonically for Pauli-Z noise, it decays suddenly for other three noises. Moreover, by studying the time evolution of entanglement of various maximally entangled four-qubit states, we indicate that the four-qubit W state is more robust under same-axis Pauli channels. Furthermore, three-qubit W state preserves more entanglement with respect to the four-qubit W state, except for the Pauli-Z noise.
Citation: International Journal of Quantum Information
PubDate: Wed, 18 Feb 2015 02:48:52 GMT
DOI: 10.1142/S0219749915500045

• Maximal entanglement entanglement-assisted quantum codes of distance three
• Authors: Luobin Guo, Qiang Fu, Ruihu Li, Liangdong Lu
Abstract: International Journal of Quantum Information, Ahead of Print. Entanglement-assisted quantum error correcting code (EAQECC) is a generalization of standard stabilizer quantum code. Maximal entanglement EAQECCs can achieve the EA-hashing bound asymptotically. In this work, we give elementary recursive constructions of quaternary zero radical codes with dual distance three for all n ≥ 4. Consequently, good maximal entanglement EAQECCs of minimum distance three for such length n are obtained. Almost all of these EAQECCs are optimal or near optimal according to the EA-quantum Hamming bound.
Citation: International Journal of Quantum Information
PubDate: Wed, 18 Feb 2015 02:48:50 GMT
DOI: 10.1142/S0219749915500021

• Quantum-state transfer between atom and macroscopically distinguishable
cavity field in Jaynes–Cummings model
• Authors: Gang Zhang, Guan-Rong Li, Zhi Song
Abstract: International Journal of Quantum Information, Ahead of Print. We present a scheme for transferring quantum state between atom and cavity field in Jaynes–Cummings model (JC) in the aid of spin-echo-like technique. It is based on the facts that the atom in a cavity can induce the generation of modified coherent states (MCSs), which can be shown to be macroscopically distinguishable, and the anti-commutation relation between the Hamiltonian and the z-component Pauli matrix. We show that this scheme is applicable for a class of cavity field states. The application on two-cavity system provides an alternative scheme for preparation of non-local superpositions of quasi-classical light states. Numerical simulation shows that the proposed schemes are efficient.
Citation: International Journal of Quantum Information
PubDate: Tue, 17 Feb 2015 09:36:56 GMT
DOI: 10.1142/S021974991550001X

• Analytic symmetric information-theoretical discord for one class of
two-qubit states
• Authors: Jun Zhang, Shao-Xiong Wu, Chang-Shui Yu, Xiaoguang Wang
Abstract: International Journal of Quantum Information, Ahead of Print. We give the analytic expression for the information-theoretical symmetric discord of one type of two-qubit X states which depend on only four real parameters. As an application, we study the symmetric discord in a model, which shows that the numerical and analytic results are well consistent.
Citation: International Journal of Quantum Information
PubDate: Thu, 12 Feb 2015 06:16:02 GMT
DOI: 10.1142/S0219749915500069

• Entangled states implemented by Bn group operators, including properties
based on HS decompositions, separability and concurrence
• Authors: Y. Ben-Aryeh
Abstract: International Journal of Quantum Information, Ahead of Print. The use of the Bn group operators is developed for implementing entangling processes for large n-qubits systems (n > 2). By operating with the Bn group operators on the computational basis of states, entangled states are obtained with properties analogous to those of the 2-qubits Bell states. Tracing any qubit from the 3-qubits Bn entangled states, we get mixed states which are separable with zero concurrence, and correspondingly with only classical correlations. These properties are generalized to larger Bn entangled states (n > 3). The properties of the Bn entangled states are analyzed by the use of Hilbert–Schmidt (HS) decompositions.
Citation: International Journal of Quantum Information
PubDate: Thu, 05 Feb 2015 02:35:24 GMT
DOI: 10.1142/S0219749914500452

• Controlling entanglement of two qubits by quantum-jump-based feedback
beyond rotating-wave approximation
• Authors: Qing Yang, Hui Liu, Xiu-Lan Zhen, Ming Yang, Zhuo-Liang Cao
Abstract: International Journal of Quantum Information, Ahead of Print. The entanglement dynamics of two identical atoms coupled to a single-mode cavity is considered. Based on the reduced non-perturbative quantum master equation method, the entanglement evolution of the two atoms with spontaneous emission under the quantum-jump-based feedback control is investigated beyond the conventional rotating-wave approximation (RWA). The research of entanglement evolution beyond RWA is a significant problem because of its importance to the field of strong coupling. The result of numerical simulations shows that an appropriate feedback control can prolong the entanglement time and increase the entanglement amplitude. The effect of synchronous control on two atoms is superior to that of one control.
Citation: International Journal of Quantum Information
PubDate: Thu, 05 Feb 2015 02:35:18 GMT
DOI: 10.1142/S0219749914500464

• Quantum discord in spin-1/2 Heisenberg chains with
Dzyaloshinkii–Moriya interaction
• Authors: Xiao San Ma, An Min Wang
Abstract: International Journal of Quantum Information, Ahead of Print. We have investigated the quantum discord (QD) of the thermal density matrix of spin-1/2 Heisenberg chains with Dzyaloshinskii–Moriya (DM) interaction. With fermionization technique, we study the mutual effect of DM interaction and the external magnetic field on the QD and the entanglement. Our analysis implies that the DM interaction can enhance the QD while the external magnetic field will shrink the QD. By a comparison between the entanglement and the QD, we find that the QD is more robust to the temperature and to the external magnetic field than the entanglement of formation (EoF) in the sense that the EoF takes a zero value while the QD does not for high temperature and strong external magnetic field. This point confirms the conclusion that there exist some separable states containing non-zero QD.
Citation: International Journal of Quantum Information
PubDate: Wed, 10 Dec 2014 09:56:33 GMT
DOI: 10.1142/S0219749914500439

• Limitations on quantum dimensionality reduction
• Authors: sales@wspc.com.sg (Aram W. Harrow)
Abstract: International Journal of Quantum Information, Ahead of Print. The Johnson–Lindenstrauss Lemma is a classic result which implies that any set of n real vectors can be compressed to O(logn) dimensions while only distorting pairwise Euclidean distances by a constant factor. Here we consider potential extensions of this result to the compression of quantum states. We show that, by contrast with the classical case, there does not exist any distribution over quantum channels that significantly reduces the dimension of quantum states while preserving the 2-norm distance with high probability. We discuss two tasks for which the 2-norm distance is indeed the correct figure of merit. In the case of the trace norm, we show that the dimension of low-rank mixed states can be reduced by up to a square root, but that essentially no dimensionality reduction is possible for highly mixed states.
PubDate: Wed, 04 Jun 2014 03:58:56 GMT
DOI: 10.1142/S0219749914400012

• EXPLICIT RELATION BETWEEN ALL LOWER BOUND TECHNIQUES FOR QUANTUM QUERY
COMPLEXITY
• Authors: LOÏCK MAGNIN et al
Abstract: International Journal of Quantum Information, Volume 0, Issue 0, Ahead of Print.
PubDate: Mon, 25 Nov 2013 06:28:10 GMT
DOI: 10.1142/S0219749913500597

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