Authors:Radhika Vathsan, Tabish Qureshi Abstract: International Journal of Quantum Information, Ahead of Print. The two-slit experiment with quantum particles provides many insights into the behavior of quantum mechanics, including Bohr’s complementarity principle. Here, we analyze Einstein’s recoiling slit version of the experiment and show how the inevitable entanglement between the particle and the recoiling slit as a which-way detector is responsible for complementarity. We derive the Englert–Greenberger–Yasin duality from this entanglement, which can also be thought of as a consequence of sum-uncertainty relations between certain complementary observables of the recoiling slit. Thus, entanglement is an integral part of the which-way detection process, and so is uncertainty, though in a completely different way from that envisaged by Bohr and Einstein. Citation: International Journal of Quantum Information PubDate: 2016-08-24T04:12:18Z DOI: 10.1142/S0219749916400311

Authors:Ariel Landau, Yakir Aharonov, Eliahu Cohen Abstract: International Journal of Quantum Information, Ahead of Print. Quantum computation strongly relies on the realization, manipulation, and control of qubits. A central method for realizing qubits is by creating a double-well potential system with a significant gap between the first two eigenvalues and the rest. In this work, we first revisit the theoretical grounds underlying the double-well qubit dynamics, then proceed to suggest novel extensions of these principles to a triple-well qutrit with periodic boundary conditions, followed by a general [math]-well analysis of qudits. These analyses are based on representations of the special unitary groups SU[math] which expose the systems’ symmetry and employ them for performing computations. We conclude with a few notes on coherence and scalability of [math]-well systems. Citation: International Journal of Quantum Information PubDate: 2016-08-23T08:56:30Z DOI: 10.1142/S0219749916500295

Authors:Amit Kumar Mohapatra, S. Balakrishnan Abstract: International Journal of Quantum Information, Ahead of Print. Wireless sensor networks (WSNs) can take the advantages by utilizing the security schemes based on the concepts of quantum computation and cryptography. However, quantum wireless sensor networks (QWSNs) are shown to have many practical constraints. One of the constraints is the number of entangled qubits which is very high in the quantum security scheme proposed by [Nagy et al., Nat. Comput. 9 (2010) 819]. In this work, we propose a modification of the security scheme introduced by Nagy et al. and hence the reduction in the number of entangled qubits is shown. Further, the modified scheme can overcome some of the constraints in the QWSNs. Citation: International Journal of Quantum Information PubDate: 2016-08-22T09:56:06Z DOI: 10.1142/S0219749916500258

Authors:Partha Ghose Abstract: International Journal of Quantum Information, Ahead of Print. An overview is given of the nature of the quantum mechanical wave function. Citation: International Journal of Quantum Information PubDate: 2016-08-22T09:56:05Z DOI: 10.1142/S021974991640030X

Authors:Mojtaba Jafarpour, Negar Naderi Abstract: International Journal of Quantum Information, Ahead of Print. We study qutrit teleportation and its fidelity in the presence and absence of intrinsic decoherence through a qutrit channel. The channel consists of a Heisenberg chain with [math] interaction model and the intrinsic decoherence is implemented through the Milburn model. It is shown that while the fidelity diminishes due to intrinsic decoherence, it may be enhanced if the channel is initially in an entangled state. It is also observed that, for stronger intrinsic decoherence, the initial entanglement of the channel is more effective in enhancing of fidelity. Citation: International Journal of Quantum Information PubDate: 2016-08-22T09:56:05Z DOI: 10.1142/S0219749916500283

Authors:Karthik S. Joshi, R. Srikanth, Urbasi Sinha Abstract: International Journal of Quantum Information, Ahead of Print. More general probability sum-rules for describing interference found in quantum mechanics (QM) were formulated by Sorkin in a hierarchy of such rules. The additivity of classical measure theory corresponds to the second sum-rule. QM violates this rule, but satisfies the third and higher sum-rules. This evokes the question of whether there are physical principles that forbid their violation. We show that in a theory that is indistinguishable from quantum mechanics in first and second-order interferences, the violation of higher sum-rules allows for superluminal signaling, essentially because probability measures can be contextual in such theories. Citation: International Journal of Quantum Information PubDate: 2016-08-19T09:31:43Z DOI: 10.1142/S0219749916500246

Authors:Sujit K Choudhary, Pankaj Agrawal Abstract: International Journal of Quantum Information, Ahead of Print. Certain predictions of quantum theory are not compatible with the notion of local-realism. This was the content of Bell’s famous theorem of the year 1964. Bell proved this with the help of an inequality, famously known as Bell’s inequality. The alternative proofs of Bell’s theorem without using Bell’s inequality are known as “nonlocality without inequality (NLWI)” proofs. We review one such proof namely the Hardy’s proof which due to its simplicity and generality has been considered the best version of Bell’s theorem. Citation: International Journal of Quantum Information PubDate: 2016-08-19T09:31:35Z DOI: 10.1142/S0219749916400359

Authors:Mark Byrd, Russell Ceballos, Eric Chitambar Abstract: International Journal of Quantum Information, Ahead of Print. Quantum systems which interact with an unknown environment cannot be described in terms of a unitary evolution on the system alone. For such evolution one can use a map from one density operator to another and use any other known information to model the system. Such maps are required to be positive (at least on their domain) — they take positive density operators to positive density operators — so as to be physically reasonable. A map [math] which is positive but not completely positive (CP) is one which takes positive operators to positive operators, but when extended by the identity [math], i.e. [math] does not give a positive map for some [math]. The map is CP if and only if the extension is positive for all [math]. Recently some effort has been put forth to try to understand if, and/or, under what circumstances one might utilize a non-CP map. Here, after a tutorial-type introduction to maps from one density operator to another, some examples which do not fit the standard prescription (SP) for deriving a CP map are given. In cases where the physical system is constrained by some knowledge of the interaction, it is possible that the SP cannot be used directly. Our example is robust to changes in the initial and final conditions. Citation: International Journal of Quantum Information PubDate: 2016-08-18T04:07:20Z DOI: 10.1142/S0219749916400232

Authors:C. S. Unnikrishnan Abstract: International Journal of Quantum Information, Ahead of Print. Gibbs paradox in the context of statistical mechanics addresses the issue of additivity of entropy of mixing gases. The usual discussion attributes the paradoxical situation to classical distinguishability of identical particles and credits quantum theory for enabling indistinguishability of identical particles to solve the problem. We argue that indistinguishability of identical particles is already a feature in classical mechanics and this is clearly brought out when the problem is treated in the language of information and associated entropy. We pinpoint the physical criteria for indistinguishability that is crucial for the treatment of the Gibbs’ problem and the consistency of its solution with conventional thermodynamics. Quantum mechanics provides a quantitative criterion, not possible in the classical picture, for the degree of indistinguishability in terms of visibility of quantum interference, or overlap of the states as pointed out by von Neumann, thereby endowing the entropy expression with mathematical continuity and physical reasonableness. Citation: International Journal of Quantum Information PubDate: 2016-08-18T04:07:19Z DOI: 10.1142/S0219749916400372

Authors:Guruprasad Kar, Manik Banik Abstract: International Journal of Quantum Information, Ahead of Print. In 1935, Albert Einstein and two colleagues, Boris Podolsky and Nathan Rosen (EPR) developed a thought experiment to demonstrate what they felt was a lack of completeness in quantum mechanics (QM). EPR also postulated the existence of more fundamental theory where physical reality of any system would be completely described by the variables/states of that fundamental theory. This variable is commonly called hidden variable and the theory is called hidden variable theory (HVT). In 1964, John Bell proposed an empirically verifiable criterion to test for the existence of these HVTs. He derived an inequality, which must be satisfied by any theory that fulfill the conditions of locality and reality. He also showed that QM, as it violates this inequality, is incompatible with any local-realistic theory. Later it has been shown that Bell’s inequality (BI) can be derived from different set of assumptions and it also find applications in useful information theoretic protocols. In this review, we will discuss various foundational as well as information theoretic implications of BI. We will also discuss about some restricted nonlocal feature of quantum nonlocality and elaborate the role of Uncertainty principle and Complementarity principle in explaining this feature. Citation: International Journal of Quantum Information PubDate: 2016-08-18T04:07:18Z DOI: 10.1142/S021974991640027X

Authors:Debasis Sarkar Abstract: International Journal of Quantum Information, Ahead of Print. Entanglement is one of the most useful resources in quantum information processing. It is effectively the quantum correlation between different subsystems of a composite system. Mathematically, one of the most hard tasks in quantum mechanics is to quantify entanglement. However, progress in this field is remarkable but not complete yet. There are many things to do with quantification of entanglement. In this review, we will discuss some of the important measures of bipartite entanglement. Citation: International Journal of Quantum Information PubDate: 2016-08-18T04:07:17Z DOI: 10.1142/S0219749916400244

Authors:Tabish Qureshi, Pravabati Chingangbam, Sheeba Shafaq Abstract: International Journal of Quantum Information, Ahead of Print. The ghost interference observed for entangled photons is theoretically analyzed using wave-packet dynamics. It is shown that ghost interference is a combined effect of virtual double-slit creation due to entanglement, and quantum erasure of which-path information for the interfering photon. For the case where the two photons are of different color, it is shown that fringe width of the interfering photon depends not only on its own wavelength, but also on the wavelength of the other photon which it is entangled with. Citation: International Journal of Quantum Information PubDate: 2016-08-18T04:07:16Z DOI: 10.1142/S0219749916400360

Authors:Y. Ben-Aryeh, A. Mann Abstract: International Journal of Quantum Information, Ahead of Print. Hilbert–Schmidt (HS) decompositions are employed for analyzing systems of [math]-qubit, and a qubit with a qudit. Negative eigenvalues, obtained by partial-transpose (PT) plus local unitary (PTU) transformations for one qubit from the whole system, are used for indicating entanglement/separability. A sufficient criterion for full separability of the [math]-qubit and qubit–qudit systems is given. We use the singular value decomposition (SVD) for improving the criterion for full separability. General properties of entanglement and separability are analyzed for a system of a qubit and a qudit and [math]-qubit systems, with emphasis on maximally disordered subsystems (MDS) (i.e. density matrices for which tracing over any subsystem gives the unit density matrix). A sufficient condition that [math] (MDS) is not separable is that it has an eigenvalue larger than [math] for a qubit and a qudit, and larger than [math] for [math]-qubit system. The PTU transformation does not change the eigenvalues of the [math]-qubit MDS density matrices for odd [math]. Thus, the Peres–Horodecki (PH) criterion does not give any information about entanglement of these density matrices. The PH criterion may be useful for indicating inseparability for even [math]. The changes of the entanglement and separability properties of the GHZ state, the Braid entangled state and the [math] state by mixing them with white noise are analyzed by the use of the present methods. The entanglement and separability properties of the GHZ-diagonal density matrices, composed of mixture of 8[math]GHZ density matrices with probabilities [math], is analyzed as function of these probabilities. In some cases, we show that the PH criterion is both sufficient and necessary. Citation: International Journal of Quantum Information PubDate: 2016-08-18T04:07:13Z DOI: 10.1142/S0219749916500301

Authors:Sai Vinjanampathy, Kavan Modi Abstract: International Journal of Quantum Information, Ahead of Print. Completely positive trace preserving (CPTP) maps are essential for the formulation of the second law of thermodynamics. The dynamics of quantum systems initially correlated with their environments are in general not described by such maps. We explore, how this issue can be fixed by describing the classical analogue of this problem. We consider initially correlated probability distributions, whose subsequent system dynamics is ill-described by stochastic maps, and prescribe the correct way to describe the dynamics. We use this prescription to discuss the classical version of the second law, valid for initially correlated probability distributions. Citation: International Journal of Quantum Information PubDate: 2016-08-15T08:31:20Z DOI: 10.1142/S0219749916400335

Authors:Bob Coecke, Aleks Kissinger Abstract: International Journal of Quantum Information, Ahead of Print. This is the second part of a three-part overview, in which we derive the category-theoretic backbone of quantum theory from a process ontology, treating quantum theory as a theory of systems, processes and their interactions. In this part, we focus on classical–quantum interaction. Classical and quantum systems are treated as distinct types, of which the respective behavioral properties are specified in terms of processes and their compositions. In particular, classicality is witnessed by ‘spiders’ which fuse together whenever they connect. We define mixedness and show that pure processes are extremal in the space of all processes, and we define entanglement and show that quantum theory indeed exhibits entanglement. We discuss the classification of tripartite qubit entanglement and show that both the GHZ-state and the W-state come from spider-like families of processes, which differ only in how they behave when they are connected by two or more wires. We define measurements and provide fully comprehensive descriptions of several quantum protocols involving classical data flow. Finally, we give a notion of ‘genuine quantumness’, from which special processes called ‘phase spiders’ arise, and get a first glimpse of quantum nonlocality. Citation: International Journal of Quantum Information PubDate: 2016-08-15T08:31:17Z DOI: 10.1142/S0219749916400207

Authors:Pankaj Agrawal, Sk Sazim, Indranil Chakrabarty, Arun K. Pati Abstract: International Journal of Quantum Information, Ahead of Print. It has been suggested that there may exist quantum correlations that go beyond entanglement. The existence of such correlations can be revealed by information theoretic quantities such as quantum discord, but not by the conventional measures of entanglement. We argue that a state displays quantumness, that can be of local and nonlocal origin. Information theoretic measures not only characterize the nonlocal quantumness, but also the local quantumness, such as the “local superposition”. This can be a reason, why such measures are nonzero, when there is no entanglement. We consider a generalized version of the Werner state to demonstrate the interplay of local quantumness, nonlocal quantumness and classical mixedness of a state. Citation: International Journal of Quantum Information PubDate: 2016-08-15T08:31:13Z DOI: 10.1142/S0219749916400347

Authors:Indrani Chattopadhyay, Debasis Sarkar Abstract: International Journal of Quantum Information, Ahead of Print. In this paper, we discuss the issue of distinguishing a pair of quantum operation in general. We use Krause theorem for representing the operations in unitary form. This supports the existence of pair of quantum operations that are not locally distinguishable, but distinguishable in asymptotic sense in some higher dimensional system. The process can even be successful without any use of the entangled initial state. Citation: International Journal of Quantum Information PubDate: 2016-08-15T08:31:12Z DOI: 10.1142/S0219749916400281

Authors:Xiao-Ning Qi, Yong Zhang Abstract: International Journal of Quantum Information, Ahead of Print. Nitrogen-vacancy (NV) centers implanted beneath the diamond surface have been demonstrated to be effective in the processing of controlling and reading-out. In this paper, NV center entangled with the fluorine nuclei collective ensemble is simplified to Jaynes–Cummings (JC) model. Based on this system, we discussed the implementation of quantum state storage and single-qubit quantum gate. Citation: International Journal of Quantum Information PubDate: 2016-08-10T08:40:54Z DOI: 10.1142/S021974991650026X

Authors:P. Chithrabhanu, A. Aadhi, Salla Gangi Reddy, Shashi Prabhakar, R. P. Singh Abstract: International Journal of Quantum Information, Ahead of Print. Using classical laser beams, we generate a general complex superposition state, cebit, of orbital angular momentum (OAM) of light. We use a nonseparable beam of polarization and OAM generated by a modified Sagnac interferometer for the generation of OAM cebits which can be represented as points on the OAM Poincaré sphere. The general cebit state is represented as a function of the rotation angle of the wave plates so that one can easily generate the required state. Citation: International Journal of Quantum Information PubDate: 2016-08-10T08:40:53Z DOI: 10.1142/S0219749916400323

Authors:V. Subrahmanyam Abstract: International Journal of Quantum Information, Ahead of Print. The correlations between a pair of spins in a many-spin state encoded in the diagonal and off-diagonal spin–spin correlation functions. These spin functions determine the quantum correlation measures, like pair-wise concurrence, quantum discord and other measures of quantum information. We show that for isotropic and translationally invariant states, the quantum correlations depend only on the diagonal spin correlation function. The pair concurrence shows a strict short-ranged behavior. The distribution of concurrence for a random W-like state exhibits a long tail for both time-reversal invariant states and for states that break the time reversal. The quantum discord can be related to the diagonal spin correlation function. As the spin function is long range close to a critical point, analogously the quantum discord exhibits a long range behavior. For the isotropi state, the conditional entropy distribution is a Dirac delta function, whereas it has a twin-peak structure for the anisotropic model. Citation: International Journal of Quantum Information PubDate: 2016-08-04T03:06:36Z DOI: 10.1142/S0219749916400293

Authors:T. R. Govindarajan Abstract: International Journal of Quantum Information, Ahead of Print. Quantum theory as formulated in conventional framework using statevectors in Hilbert spaces misses the statistical nature of the underlying quantum physics. Formulation using operators [math] algebra and density matrices appropriately captures this feature in addition leading to the correct formulation of particle identity. In this framework, Hilbert space is an emergent concept. Problems related to anomalies and quantum epistemology are discussed. Citation: International Journal of Quantum Information PubDate: 2016-08-04T03:06:30Z DOI: 10.1142/S0219749916400268

Authors:A. S. Majumdar, T. Pramanik Abstract: International Journal of Quantum Information, Ahead of Print. We discuss some applications of various versions of uncertainty relations for both discrete and continuous variables in the context of quantum information theory. The Heisenberg uncertainty relation enables demonstration of the Einstein, Podolsky and Rosen (EPR) paradox. Entropic uncertainty relations (EURs) are used to reveal quantum steering for non-Gaussian continuous variable states. EURs for discrete variables are studied in the context of quantum memory where fine-graining yields the optimum lower bound of uncertainty. The fine-grained uncertainty relation is used to obtain connections between uncertainty and the nonlocality of retrieval games for bipartite and tripartite systems. The Robertson-Schrödinger (RS) uncertainty relation is applied for distinguishing pure and mixed states of discrete variables. Citation: International Journal of Quantum Information PubDate: 2016-08-04T03:06:28Z DOI: 10.1142/S0219749916400220

Authors:Chitra Shukla, Anindita Banerjee, Anirban Pathak, R. Srikanth Abstract: International Journal of Quantum Information, Ahead of Print. In majority of protocols of secure quantum communication (such as, BB84, B92, etc.), the unconditional security of the protocols are obtained by using conjugate coding (two or more mutually unbiased bases (MUBs)). Initially, all the conjugate-coding-based protocols of secure quantum communication were restricted to quantum key distribution (QKD), but later on they were extended to other cryptographic tasks (such as, secure direct quantum communication and quantum key agreement). In contrast to the conjugate-coding-based protocols, a few completely orthogonal-state-based protocols of unconditionally secure QKD (such as, Goldenberg–Vaidman and N09) were also proposed. However, till the recent past, orthogonal-state-based protocols were only a theoretical concept and were limited to QKD. Only recently, orthogonal-state-based protocols of QKD are experimentally realized and extended to cryptographic tasks beyond QKD. This paper aims to briefly review the orthogonal-state-based protocols of secure quantum communication that are recently introduced by our group and other researchers. Citation: International Journal of Quantum Information PubDate: 2016-08-04T03:06:23Z DOI: 10.1142/S0219749916400219

Authors:Cai Zhang, Haozhen Situ, Qin Li, Guang Ping He Abstract: International Journal of Quantum Information, Ahead of Print. We firstly propose a simultaneous dense coding protocol with two-photon four-qubit cluster states in which two receivers can simultaneously get their respective classical information sent by a sender. Because each photon has two degrees of freedom, the protocol will achieve a high transmittance. The security of the simultaneous dense coding protocol has also been analyzed. Secondly, we investigate how to simultaneously teleport two different quantum states with polarization and path degree of freedom using cluster states to two receivers, respectively, and discuss its security. The preparation and transmission of two-photon four-qubit cluster states is less difficult than that of four-photon entangled states, and it has been experimentally generated with nearly perfect fidelity and high generation rate. Thus, our protocols are feasible with current quantum techniques. Citation: International Journal of Quantum Information PubDate: 2016-08-03T03:50:55Z DOI: 10.1142/S0219749916500234

Authors:Hamid Arian Zad, Hossein Movahhedian Abstract: International Journal of Quantum Information, Ahead of Print. Heat capacity of a mixed-three-spin (1/2,1,1/2) antiferromagnetic XXX Heisenberg chain is precisely investigated by use of the partition function of the system for which, spins (1,1/2) have coupling constant [math] and spins (1/2,1/2) have coupling constant [math]. We verify tripartite entanglement for the model by means of the convex roof extended negativity (CREN) and concurrence as functions of temperature T, homogeneous magnetic field B and the coupling constants [math] and [math]. As shown in our previous work, [H. A. Zad, Chin. Phys. B 25 (2016) 030303.] the temperature, the magnetic field and the coupling constants dependences of the heat capacity for such spin system have different behaviors for the entangled and separable states, hence, we did some useful comparisons between this quantity and negativities of its organized bipartite (sub)systems at entangled and separable states. Here, we compare the heat capacity of the mixed-three-spin (1/2,1,1/2) system with the CREN and the tripartite concurrence (as measures of the tripartite entanglement) at low temperature. Ground state phase transitions, and also, transition from ground state to some excited states are explained in detail for this system at zero temperature. Finally, we investigate the heat capacity behavior around those critical points in which these quantum phase transitions occur. Citation: International Journal of Quantum Information PubDate: 2016-08-02T04:05:13Z DOI: 10.1142/S0219749916500209

Authors:E Wu, FengZhi Li, XueFeng Zhang, YongHong Ma Abstract: International Journal of Quantum Information, Ahead of Print. We propose a scheme to generate the case of macroscopic entanglement in the optomechanical system, which consist of Fabry–Perot cavity and a mechanical oscillator by applying a homodyne-mediated quantum feedback. We explore the effect of feedback on the entanglement in vacuum and coherent state, respectively. The results show that the introduction of quantum feedback can increase the entanglement effectively between the cavity mode and the oscillator mode. Citation: International Journal of Quantum Information PubDate: 2016-07-28T08:24:49Z DOI: 10.1142/S0219749916500222

Authors:Carlos Ortega Laurel, Shi-Hai Dong, M. Cruz-Irisson Abstract: International Journal of Quantum Information, Ahead of Print. This paper presents a steganographical algorithm based on least significant bit (LSB) from the most significant bit information (MSBI) and the equivalence of a bit pixel image to a quantum pixel image, which permits to make the information communicate secretly onto quantum pixel images for its secure transmission through insecure channels. This algorithm offers higher security since it exploits the Shannon entropy for an image. Citation: International Journal of Quantum Information PubDate: 2016-07-15T07:15:06Z DOI: 10.1142/S0219749916500210

Authors:T. Kaufherr Abstract: International Journal of Quantum Information, Ahead of Print. The gauge invariant nonlocal quantum dynamics that is responsible for the Aharonov–Bohm (AB) effect is described. It is shown that it may be verified experimentally. Citation: International Journal of Quantum Information PubDate: 2016-06-10T08:57:58Z DOI: 10.1142/S021974991640013X

Authors:Maria Luisa Dalla Chiara, Roberto Giuntini, Giuseppe Sergioli, Roberto Leporini Abstract: International Journal of Quantum Information, Ahead of Print. Classical and quantum parallelism are deeply different, although it is sometimes claimed that quantum Turing machines are nothing but special examples of classical probabilistic machines. We introduce the concepts of deterministic state machine, classical probabilistic state machine and quantum state machine. On this basis, we discuss the question: To what extent can quantum state machines be simulated by classical probabilistic state machines? Each state machine is devoted to a single task determined by its program. Real computers, however, behave differently, being able to solve different kinds of problems. This capacity can be modeled, in the quantum case, by the mathematical notion of abstract quantum computing machine, whose different programs determine different quantum state machines. The computations of abstract quantum computing machines can be linguistically described by the formulas of a particular form of quantum logic, termed quantum computational logic. Citation: International Journal of Quantum Information PubDate: 2016-06-08T10:31:51Z DOI: 10.1142/S0219749916400190

Authors:Andrei Khrennikov Abstract: International Journal of Quantum Information, Ahead of Print. Recent tremendous development of quantum information theory has led to a number of quantum technological projects, e.g. quantum random generators. This development had stimulated a new wave of interest in quantum foundations. One of the most intriguing problems of quantum foundations is the elaboration of a consistent and commonly accepted interpretation of a quantum state. Closely related problem is the clarification of the notion of quantum randomness and its interrelation with classical randomness. In this short review, we shall discuss basics of classical theory of randomness (which by itself is very complex and characterized by diversity of approaches) and compare it with irreducible quantum randomness. We also discuss briefly “digital philosophy”, its role in physics (classical and quantum) and its coupling to the information interpretation of quantum mechanics (QM). Citation: International Journal of Quantum Information PubDate: 2016-05-27T02:56:09Z DOI: 10.1142/S0219749916400098

Authors:Florin Moldoveanu Abstract: International Journal of Quantum Information, Ahead of Print. Recent quantum reconstruction projects demand pure unitary time evolution which seems to contradict the collapse postulate. Inspired by Zurek’s environment assisted invariance idea, a natural unitary realization of wave function collapse is proposed using Grothendieck group construction for the tensor product commutative monoid. Citation: International Journal of Quantum Information PubDate: 2016-05-24T03:41:56Z DOI: 10.1142/S0219749916400153

Authors:Habib Ouerdiane Abstract: International Journal of Quantum Information, Ahead of Print. We study an evolution equation associated with the integer power of the Gross Laplacian [math] and a potential function V on an infinite-dimensional space. The initial condition is a generalized function. The main technique we use is the representation of the Gross Laplacian as a convolution operator. This representation enables us to apply the convolution calculus on a suitable distribution space to obtain the explicit solution of the perturbed evolution equation. Our results generalize those previously obtained by Hochberg [K. J. Hochberg, Ann. Probab. 6 (1978) 433.] in the one-dimensional case with [math], as well as by Barhoumi–Kuo–Ouerdiane for the case [math] (See Ref. [A. Barhoumi, H. H. Kuo and H. Ouerdiane, Soochow J. Math. 32 (2006) 113.]). Citation: International Journal of Quantum Information PubDate: 2016-05-24T03:41:54Z DOI: 10.1142/S0219749916400189

Authors:L. Vaidman Abstract: International Journal of Quantum Information, Ahead of Print. The counterfactuality of recently proposed protocols is analyzed. A definition of “counterfactuality” is offered and it is argued that an interaction-free measurement (IFM) of the presence of an opaque object can be named “counterfactual”, while proposed “counterfactual” measurements of the absence of such objects are not counterfactual. The quantum key distribution protocols which rely only on measurements of the presence of the object are counterfactual, but quantum direct communication protocols are not. Therefore, the name “counterfactual” is not appropriate for recent “counterfactual” protocols which transfer quantum states by quantum direct communication. Citation: International Journal of Quantum Information PubDate: 2016-05-20T09:38:14Z DOI: 10.1142/S0219749916400128

Authors:Stephan Sponar Abstract: International Journal of Quantum Information, Ahead of Print. Heisenberg’s uncertainty principle in a formulation of uncertainties, intrinsic to any quantum system, is rigorously proven and demonstrated in various quantum systems. Nevertheless, Heisenberg’s original formulation of the uncertainty principle was given in terms of a reciprocal relation between the error of a position measurement and the thereby induced disturbance on a subsequent momentum measurement. However, a naive generalization of a Heisenberg-type error-disturbance relation for arbitrary observables is not valid. An alternative universally valid relation was derived by Ozawa in 2003. Though universally valid, Ozawa’s relation is not optimal. Recently, Branciard has derived a tight error-disturbance uncertainty relation (EDUR), describing the optimal trade-off between error and disturbance under certain conditions. Here, we report a neutron-optical experiment that records the error of a spin-component measurement, as well as the disturbance caused on another spin-component to test EDURs. We demonstrate that Heisenberg’s original EDUR is violated, and Ozawa’s and Branciard’s EDURs are valid in a wide range of experimental parameters, as well as the tightness of Branciard’s relation. Citation: International Journal of Quantum Information PubDate: 2016-05-20T09:38:13Z DOI: 10.1142/S0219749916400165

Abstract: International Journal of Quantum Information, Ahead of Print. By performing X-rays measurements in the underground laboratory of Gran Sasso, LNGS-INFN, we test a basic principle of quantum mechanics: the Pauli exclusion principle (PEP). In the future, we aim to use a similar experimental technique to search for X-rays as a signature of the spontaneous collapse of the wave function predicted by continuous spontaneous localization theories. We present the achieved results of the VIP experiment and the future plans to gain two orders of magnitude in testing PEP with the recently VIP2 setup installed at Gran Sasso. Citation: International Journal of Quantum Information PubDate: 2016-05-19T11:35:04Z DOI: 10.1142/S0219749916400177

Authors:Elena R. Loubenets Abstract: International Journal of Quantum Information, Ahead of Print. We specify the local quasi hidden variable (LqHV) model reproducing the probabilistic description of all N-partite joint von Neumann measurements on an N-qudit state. Via this local probability model, we derive a new upper bound on the maximal violation by an N-qudit state of Bell inequalities of any type (either on correlation functions or on joint probabilities) for S observables per site. This new upper bound not only improves for all [math] S and d the corresponding results available for general Bell inequalities in the literature but also, for the N-qubit case with two observables per site, reduces exactly to the attainable upper bound known for quantum violations of correlation [math] setting Bell inequalities in a dichotomic case. Citation: International Journal of Quantum Information PubDate: 2016-05-19T11:35:03Z DOI: 10.1142/S0219749916400104

Authors:G. Adenier, D. Calonico, S. Micalizio, N. Samantaray, I. P. Degiovanni, I. Ruo Berchera Abstract: International Journal of Quantum Information, Ahead of Print. Four-wave mixing (4WM) is a known source of intense non-classical twin beams. It can be generated when an intense laser beam (the pump) and a weak laser beam (the seed) overlap in a [math] medium (here Cesium vapor), with frequencies close to resonance with atomic transitions. The twin beams generated by 4WM have frequencies naturally close to atomic transitions, and can be intense (gain [math]) even in the CW pump regime, which is not the case for PDC [math] phenomenon in nonlinear crystals. So, 4WM is well suited for atom-light interaction and atom-based quantum-protocols. Here, we present the first realization of a source of 4-wave mixing exploiting [math] line of Cesium atoms. Citation: International Journal of Quantum Information PubDate: 2016-05-19T03:27:06Z DOI: 10.1142/S0219749916400141

Abstract: International Journal of Quantum Information, Ahead of Print. We propose an adynamical interpretation of quantum theory called Relational Blockworld (RBW) where the fundamental ontological element is a 4D graphical amalgam of space, time and sources called a “spacetimesource element.” These are fundamental elements of space, time and sources, not source elements in space and time. The transition amplitude for a spacetimesource element is computed using a path integral with discrete graphical action. The action for a spacetimesource element is constructed from a difference matrix K and source vector J on the graph, as in lattice gauge theory. K is constructed from graphical field gradients so that it contains a non-trivial null space and J is then restricted to the row space of K, so that it is divergence-free and represents a conserved exchange of energy–momentum. This construct of K and J represents an adynamical global constraint between sources, the spacetime metric and the energy–momentum content of the spacetimesource element, rather than a dynamical law for time-evolved entities. To illustrate this interpretation, we explain the simple EPR-Bell and twin-slit experiments. This interpretation of quantum mechanics constitutes a realist, psi-epistemic model that might underwrite certain information-theoretic accounts of the quantum. Citation: International Journal of Quantum Information PubDate: 2016-05-13T06:45:32Z DOI: 10.1142/S0219749916400074

Authors:Satoshi Iriyama, Masanori Ohya Abstract: International Journal of Quantum Information, Ahead of Print. The adaptive dynamics is known as a new mathematics to treat with a complex phenomena, for example, chaos, quantum algorithm and psychological phenomena. In this paper, we briefly review the notion of the adaptive dynamics, and explain the definition of the generalized Turing machine (GTM) and recognition process represented by the Fock space. Moreover, we show that there exists the quantum channel which is described by the GKSL master equation to achieve the Chaos Amplifier used in [M. Ohya and I. V. Volovich, J. Opt. B 5(6) (2003) 639., M. Ohya and I. V. Volovich, Rep. Math. Phys. 52(1) (2003) 25.] Citation: International Journal of Quantum Information PubDate: 2016-05-13T06:45:28Z DOI: 10.1142/S0219749916400086

Authors:M. Kupczynski Abstract: International Journal of Quantum Information, Ahead of Print. Entangled physical systems are an important resource in quantum information. Many papers were published trying to grasp the meaning of entanglement. It was noticed that a Hilbert space of possible state vectors of compound physical system can be partitioned by introducing various tensor product structures induced by the experimentally accessible observables (interactions and measurements). In this sense, the entanglement is relative to a particular set of experimental capabilities. Inspired by these results some authors claim that in fact all quantum states are entangled. In this paper, we show that this claim is incorrect and we discuss in operational way differences existing between separable and entangled states. A sufficient condition for entanglement is the violation of Bell–CHSH-CH inequalities and/or steering inequalities. Since there exist experiments outside the domain of quantum physics violating these inequalities therefore in the operational approach one cannot say that the entanglement is an exclusive quantum phenomenon. We also explain that an unambiguous experimental certification of the entanglement is a difficult task because classical statistical significance tests may not be trusted if sample homogeneity cannot be tested or is not tested carefully enough. Citation: International Journal of Quantum Information PubDate: 2016-05-11T11:15:48Z DOI: 10.1142/S0219749916400037

Authors:Hans-Thomas Elze Abstract: International Journal of Quantum Information, Ahead of Print. Cellular automata (CA) can show well known features of quantum mechanics (QM), such as a linear updating rule that resembles a discretized form of the Schrödinger equation together with its conservation laws. Surprisingly, a whole class of “natural” Hamiltonian CA, which are based entirely on integer-valued variables and couplings and derived from an action principle, can be mapped reversibly to continuum models with the help of sampling theory. This results in “deformed” quantum mechanical models with a finite discreteness scale l, which for [math] reproduce the familiar continuum limit. Presently, we show, in particular, how such automata can form “multipartite” systems consistently with the tensor product structures of non-relativistic many-body QM, while maintaining the linearity of dynamics. Consequently, the superposition principle is fully operative already on the level of these primordial discrete deterministic automata, including the essential quantum effects of interference and entanglement. Citation: International Journal of Quantum Information PubDate: 2016-05-11T11:15:45Z DOI: 10.1142/S0219749916400013

Authors:Francesco De Martini, Enrico Santamato Abstract: International Journal of Quantum Information, Ahead of Print. The traditional standard theory of quantum mechanics is unable to solve the spin-statistics problem, i.e. to justify the utterly important “Pauli Exclusion Principle” but by the adoption of the complex standard relativistic quantum field theory. In a recent paper [E. Santamato and F. D. De Martini, Found. Phys. 45 (2015) 858] we presented a complete proof of the spin-statistics problem in the nonrelativistic approximation on the basis of the “Conformal Quantum Geometrodynamics” (CQG). In this paper, by the same theory, the proof of the spin-statistics theorem (SST) is extended to the relativistic domain in the scenario of curved spacetime. No relativistic quantum field operators are used in the present proof and the particle exchange properties are drawn from rotational invariance rather than from Lorentz invariance. Our relativistic approach allows to formulate a manifestly step-by-step Weyl gauge invariant theory and to emphasize some fundamental aspects of group theory in the demonstration. As in the nonrelativistic case, we find once more that the “intrinsic helicity” of the elementary particles enters naturally into play. It is therefore this property, not considered in the standard quantum mechanics (SQM), which determines the correct spin-statistics connection observed in Nature. Citation: International Journal of Quantum Information PubDate: 2016-04-28T07:45:44Z DOI: 10.1142/S0219749916400116

Authors:Noboru Watanabe Abstract: International Journal of Quantum Information, Ahead of Print. We review some notions for quantum dynamical entropies. The dynamical entropy of quantum systems is discussed and a numerical computation of the dynamical entropy is carried for the open system dynamics. Citation: International Journal of Quantum Information PubDate: 2016-04-28T07:45:36Z DOI: 10.1142/S0219749916400050

Authors:Brian R. La Cour, Corey I. Ostrove, Granville E. Ott, Michael J. Starkey, Gary R. Wilson Abstract: International Journal of Quantum Information, Ahead of Print. This paper describes a novel approach to emulate a universal quantum computer with a wholly classical system, one that uses a signal of bounded duration and amplitude to represent an arbitrary quantum state. The signal may be of any modality (e.g. acoustic, electromagnetic, etc.) but this paper will focus on electronic signals. Individual qubits are represented by in-phase and quadrature sinusoidal signals, while unitary gate operations are performed using simple analog electronic circuit devices. In this manner, the Hilbert space structure of a multi-qubit quantum state, as well as a universal set of gate operations, may be fully emulated classically. Results from a programmable prototype system are presented and discussed. Citation: International Journal of Quantum Information PubDate: 2016-04-07T08:50:53Z DOI: 10.1142/S0219749916400049

Abstract: International Journal of Quantum Information, Ahead of Print. We discuss the recently observed “loophole free” violation of Bell’s inequalities in the framework of a physically realist view of quantum mechanics (QM), which requires that physical properties are attributed jointly to a system, and to the context in which it is embedded. This approach is clearly different from classical realism, but it does define a meaningful “quantum realism” from a general philosophical point of view. Consistently with Bell test experiments, this quantum realism embeds some form of non-locality, but does not contain any action at a distance, in agreement with QM. Citation: International Journal of Quantum Information PubDate: 2016-04-07T08:50:52Z DOI: 10.1142/S0219749916400025

Authors:S. A. Rashkovskiy Abstract: International Journal of Quantum Information, Ahead of Print. It is shown that the Schrödinger equation can be written in the form of the diffusion equation for classical particles moving in a continuous space. A class of classical random processes described by the Schrödinger equation is considered. It is shown that such classical random processes can be used as a tool for the numerical solution of the Schrödinger equation. Citation: International Journal of Quantum Information PubDate: 2016-04-07T08:50:50Z DOI: 10.1142/S0219749916400062