Quantum Secure Dialogue with Quantum Encryption

How to solve the information leakage problem has become the research focus of quantum dialogue. In this paper, in order to overcome the information leakage problem in quantum dialogue, a novel approach for sharing the initial quantum state privately between communicators, i.e., quantum encryption sharing, is proposed by utilizing the idea of quantum encryption. The proposed protocol uses EPR pairs as the private quantum key to encrypt and decrypt the traveling photons, which can be repeatedly used after rotation. Due to quantum encryption sharing, the public announcement on the state of the initial quantum state is omitted, thus the information leakage problem is overcome. The information-theoretical efficiency of the proposed protocol is nearly 100%, much higher than previous information leakage resistant quantum dialogue protocols. Moreover, the proposed protocol only needs single-photon measurements and nearly uses single photons as quantum resource so that it is convenient to implement in practice.     

Quantum Secure Dialogue with Quantum Encryption

How to solve the information leakage problem has become the research focus of quantum dialogue. In this paper, in order to overcome the information leakage problem in quantum dialogue, a novel approach for sharing the initial quantum state privately between communicators, i.e., quantum encryption sharing, is proposed by utilizing the idea of quantum encryption. The proposed protocol uses EPR pairs as the private quantum key to encrypt and decrypt the traveling photons, which can be repeatedly used after rotation. Due to quantum encryption sharing, the public announcement on the state of the initial quantum state is omitted, thus the information leakage problem is overcome.The information-theoretical efficiency of the proposed protocol is nearly 100%, much higher than previous information leakage resistant quantum dialogue protocols. Moreover, the proposed protocol only needs single-photon measurements and nearly uses single photons as quantum resource so that it is convenient to implement in practice.     

Standing waves and resonance transport mechanism in quantum networks

One-electron spin-dependent scattering problem is considered on the star-shaped 2-d quantum network consisting of a quantum well and few relatively thin leads attached to it. The resonance nature of transmission coefficients is revealed based on accurate analysis of interaction between the running spin-waves in the leads and the standing spin-waves in the quantum well. Modeling of the transport problem on the two-dimensional junction by the 1-d scattering problem on the corresponding quantum graph is discussed.     

New quantum algorithm for studying NP-complete problems

Ordinary approach to quantum algorithm is based on quantum Turing machine or quantum circuits. It is known that this approach is not powerful enough to solve NP-complete problems. In this paper we study a new approach to quantum algorithm which is a combination of the ordinary quantum algorithm with a chaotic dynamical system. We consider the satisfiability problem as an example of NP-complete problems and argue that the problem, in principle, can be solved in polynomial time by using our new quantum algorithm.     

Quantum computational complexity of the N-representability problem: QMA complete

We study the computational complexity of the N-representability problem in quantum chemistry. We show that this problem is quantum Merlin-Arthur complete, which is the quantum generalization of nondeterministic polynomial time complete. Our proof uses a simple mapping from spin systems to fermionic systems, as well as a convex optimization technique that reduces the problem of finding ground states to N representability.     

RIEMANN-HILBERT PROBLEM OF THE QUANTUM NONLINEAR SCHRÖDINGER MODEL

In this paper we present a representation of quantum Riemann-Hilbert problem of the nonlinear Schrödinger model, from which both the results of direct problem of the quantum inverse scattering method and the quantum Gelfand-Levitan equation can be given. It is pointed out that this method may be extended to any other quantum AKNS-type model.     

Vacuum energy: Quantum hydrodynamics vs. quantum gravity

We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which, in quantum gravity, transforms to the cosmological constant problem. We show that, in quantum liquids, the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid, including the radius of the liquid droplet. In the same manner, the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant, and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to the thermodynamic stability of the whole quantum vacuum.     

Quantum Dialogue Without Information Leakage Using a Single Quantum Entangled State

At present, a lot of quantum dialogue protocols have the problem of information leakage, especially the ones merely using a single quantum state as the quantum resource. In this paper, the author successfully puts forward a novel kind of information leakage resistant quantum dialogue protocol merely using a single quantum entangled state. This kind of quantum dialogue protocol uses the measurement correlation property of a single quantum entangled state to prevent the information leakage problem. Its Bell state version is illustrated in detail at first in this paper, then it is generalized to the cases of three-particle, four-particle and five-particle quantum entangled states. Different from those previous information leakage resistant quantum dialogue protocols, the proposed protocol needs neither the auxiliary quantum state nor the entanglement swapping technology of quantum state.     

The Initialization Problem in Quantum Computing

The problem of initializing phase in a quantum computing system is considered. The initialization of phases is a problem when the system is initially present in a superposition state as well as in the application of the quantum gate transformations, since each gate will introduce phase uncertainty. The accumulation of these random phases will reduce the effectiveness of the recently proposed quantum computing schemes. The paper also presents general observations on the nonlocal nature of quantum errors and the expected performance of the recently proposed quantum error-correction codes that are based on the assumption that the errors are either bit-flip or phase-flip or both. It is argued that these codes cannot directly solve the initialization problem of quantum computing.     

Quantum knitting

We analyze the connections between the mathematical theory of knots and quantum physics by addressing a number of algorithmic questions related to both knots and braid groups. Knots can be distinguished by means of “knot invariants,” among which the Jones polynomial plays a prominent role, since it can be associated with observables in topological quantum field theory. Although the problem of computing the Jones polynomial is intractable in the framework of classical complexity theory, it has been recently recognized that a quantum computer is capable of approximating it in an efficient way. The quantum algorithms discussed here represent a breakthrough for quantum computation, since approximating the Jones polynomial is actually a “universal problem,” namely, the hardest problem that a quantum computer can efficiently handle.     

Information Leakage Problem in High-Capacity Quantum Secure Communication with Authentication Using Einstein-Podolsky-Rosen Pairs

The information leakage problem often exists in bidirectional quantum secure direct communication or quantum dialogue.In this work,we find that this problem also exists in the one-way quantum secure communication protocol[Chin.Phys.Lett.32(2015) 050301].Specifically,the first bit of every four-bit message block is leaked out without awareness.A way to improve the information leakage problem is given.     

Quantum Einstein’s equations and constraints algebra

In this paper we shall address this problem: Is quantum gravity constraints algebra closed and what are the quantum Einstein’s equations. We shall investigate this problem in the de-Broglie-Bohm quantum theory framework. It is shown that the constraint algebra is weakly closed and the quantum Einstein’s equations are derived.     

Why error-prone quantum measurements have outcomes

To solve the quantum measurement problem it is necessary to construct quantum mechanical models of measurement interactions to show why properly conducted measurements always yield definite outcomes. The main barrier to a solution has been the interpretive principle that a quantum system has a definite value for an observable only if it may be described by a quantum eigenstate of the corresponding operator. I have recently proposed a solution to the measurement problem based on alternative interpretive principles. The present paper defends this proposal against recent criticisms which seek to show that it fails to solve the problem unless quantum measurements meet highly idealized conditions which no actual measurement could hope to meet. Several models of error-prone measurements are shown to lead to definite outcomes, and a general defense of the appropriateness of these models is sketched.     

Discriminating States: the quantum Chernoff bound

We consider the problem of discriminating two different quantum states in the setting of asymptotically many copies, and determine the minimal probability of error. This leads to the identification of the quantum Chernoff bound, thereby solving a long-standing open problem. The bound reduces to the classical Chernoff bound when the quantum states under consideration commute. The quantum Chernoff bound is the natural symmetric distance measure between quantum states because of its clear operational meaning and because it does not seem to share some of the undesirable features of other distance measures.     

The Improved Evolution Paths to Speedup Quantum Evolution

The quantum adiabatic evolution is very important for quantum mechanics and applied in quantum information processing to solve the difficult problem. The traditional quantum adiabatic algorithms use the linear interpolating to construct quantum evolution paths. We construct special evolution paths to speedup quantum evolutions. By choosing state-dependent correlations some constant time evolution paths may be generated. This result is very useful quantum adiabatic simulations.     

Quantum Theory and the Role of Mind in Nature

Orthodox Copenhagen quantum theory renounces the quest to understand the reality in which we are imbedded, and settles for practical rules describing connections between our observations. Many physicist have regarded this renunciation of our effort describe nature herself as premature, and John von Neumann reformulated quantum theory as a theory of an evolving objective universe interacting with human consciousness. This interaction is associated both in Copenhagen quantum theory and in von Neumann quantum theory with a sudden change that brings the objective physical state of a system in line with a subjectively felt psychical reality. The objective physical state is thereby converted from a material substrate to an informational and dispositional substrate that carries both the information incorporated into it by the psychical realities, and certain dispositions for the occurrence of future psychical realities. The present work examines and proposes solutions to two problems that have appeared to block the development of this conception of nature. The first problem is how to reconcile this theory with the principles of relativistic quantum field theory; the second problem is to understand whether, strictly within quantum theory, a person's mind can affect the activities of his brain, and if so how. Solving the first problem involves resolving a certain non-locality question. The proposed solution to the second problem is based on a postulated connection between effort, attention, and the quantum Zeno effect. This solution explains on the basic of quantum physics a large amount of heretofore unexplained data amassed by psychologists.     

Junctions of three quantum wires and the dissipative Hofstadter model

We study a junction of three quantum wires enclosing a magnetic flux. This is the simplest problem of a quantum junction between Tomonaga-Luttinger liquids in which Fermi statistics enter in a nontrivial way. We present a direct connection between this problem and the dissipative Hofstadter problem, or quantum Brownian motion in two dimensions in a periodic potential and an external magnetic field, which in turn is connected to open string theory in a background electromagnetic field. We find nontrivial fixed points corresponding to a chiral conductance tensor leading to an asymmetric flow of the current.     

Heat transport in quantum spin chains

We discuss the problem of heat conduction in quantum spin chain models. To investigate this problem it is necessary to consider the finite open system connected to heat baths. We describe two different procedures to couple the system with the reservoirs: a model of stochastic heat baths and the quantum trajectories solution of the quantum master equation. The stochastic heat bath procedure operates on the pure wave function of the isolated system, so that it is locally and periodically collapsed to a quantum state consistent with a boundary nonequilibrium state. In contrast, the quantum trajectories procedure evaluates ensemble averages in terms of the reduced density matrix operator of the system. We apply these procedures to different models of quantum spin chains and numerically show their applicability to study the heat flow.     

A secure quantum key distribution scheme based on variable quantum encoding algorithms

The security of the quantum secret key plays a critical role in quantum communications.Thus far,one problem that still exists in existing protocols is the leakage of the length of the secret key.In this letter,based on variable quantum encoding algorithms,we propose a secure quantum key distribution scheme,which can overcome the security problem involving the leakage of the secret key.Security analysis shows that the proposed scheme is both secure and effective.     

Quantum Communication and Quantum Multivariate Polynomial Interpolation

The paper is devoted to the problem of multivariate polynomial interpolation and its application to quantum secret sharing. We show that using quantum Fourier transform one can produce the protocol for quantum secret sharing distribution.