Undecidability and the Problem of Outcomes in Quantum Measurements

We argue that it is fundamentally impossible to recover information about quantum superpositions when a quantum system has interacted with a sufficiently large number of degrees of freedom of the environment. This is due to the fact that gravity imposes fundamental limitations on how accurate measurements can be. This leads to the notion of undecidability: there is no way to tell, due to fundamental limitations, if a quantum system evolved unitarily or suffered wavefunction collapse. This in turn provides a solution to the problem of outcomes in quantum measurement by providing a sharp criterion for defining when an event has taken place. We analyze in detail in examples two situations in which in principle one could recover information about quantum coherence: (a) “revivals” of coherence in the interaction of a system with the measurement apparatus and the environment and (b) the measurement of global observables of the system plus apparatus plus environment. We show in the examples that the fundamental limitations due to gravity and quantum mechanics in measurement prevent both revivals from occurring and the measurement of global observables. It can therefore be argued that the emerging picture provides a complete resolution to the measurement problem in quantum mechanics.     

Partial Measurements and the Realization of Quantum-Mechanical Counterfactuals

We propose partial measurements as a conceptual tool to understand how to operate with counterfactual claims in quantum physics. Indeed, unlike standard von Neumann measurements, partial measurements can be reversed probabilistically. We first analyze the consequences of this rather unusual feature for the principle of superposition, for the complementarity principle, and for the issue of hidden variables. Then we move on to exploring non-local contexts, by reformulating the EPR paradox, the quantum teleportation experiment, and the entanglement-swapping protocol for the situation in which one uses partial measurements followed by their stochastic reversal. This leads to a number of counter-intuitive results, which are shown to be resolved if we give up the idea of attributing reality to the wavefunction of a single quantum system.     

The Dynamics of Quantum Correlation and Its Transfer in Dissipative Systems

Quantum correlation of a general bipartite quantum state may contain not only entanglement but also the ingredient that cannot be accounted for by entanglement. In this paper, we study the dynamics of quantum correlation by virtue of quantum discord, in particular the transfer of quantum correlation in the absence of entanglement. The considered model consists of two correlated qubits with each one being coupled to an independent reservoir. We show that the reservoirs which are initially in product state can be induced quantum correlation even when the qubits are initially in separate state.     

Probability Description and Entropy of Classical and Quantum Systems

Tomographic approach to describing both the states in classical statistical mechanics and the states in quantum mechanics using the fair probability distributions is reviewed. The entropy associated with the probability distribution (tomographic entropy) for classical and quantum systems is studied. The experimental possibility to check the inequalities like the position–momentum uncertainty relations and entropic uncertainty relations are considered.     

Hamiltonian Map to Conformal Modification of Spacetime Metric: Kaluza-Klein and TeVeS

It has been shown that the orbits of motion for a wide class of non-relativistic Hamiltonian systems can be described as geodesic flows on a manifold and an associated dual by means of a conformal map. This method can be applied to a four dimensional manifold of orbits in spacetime associated with a relativistic system. We show that a relativistic Hamiltonian which generates Einstein geodesics, with the addition of a world scalar field, can be put into correspondence in this way with another Hamiltonian with conformally modified metric. Such a construction could account for part of the requirements of Bekenstein for achieving the MOND theory of Milgrom in the post-Newtonian limit. The constraints on the MOND theory imposed by the galactic rotation curves, through this correspondence, would then imply constraints on the structure of the world scalar field. We then use the fact that a Hamiltonian with vector gauge fields results, through such a conformal map, in a Kaluza-Klein type theory, and indicate how the TeVeS structure of Bekenstein and Saunders can be put into this framework. We exhibit a class of infinitesimal gauge transformations on the gauge fields U_m(x){\mathcal{U}}_{\mu}(x) which preserve the Bekenstein-Sanders condition U_mU^m=-1{\mathcal{U}}_{\mu}{\mathcal{U}}^{\mu}=-1. The underlying quantum structure giving rise to these gauge fields is a Hilbert bundle, and the gauge transformations induce a non-commutative behavior to the fields, i.e. they become of Yang-Mills type. Working in the infinitesimal gauge neighborhood of the initial Abelian theory we show that in the Abelian limit the Yang-Mills field equations provide residual nonlinear terms which may avoid the caustic singularity found by Contaldi et al.     

On the Nature of Bose-Einstein Condensation in Disordered Systems

We study the perfect Bose gas in random external potentials and show that there is generalized Bose-Einstein condensation in the random eigenstates if and only if the same occurs in the one-particle kinetic-energy eigenstates, which corresponds to the generalized condensation of the free Bose gas. Moreover, we prove that the amounts of both condensate densities are equal. Our method is based on the derivation of an explicit formula for the occupation measure in the one-body kinetic-energy eigenstates which describes the repartition of particles among these non-random states. This technique can be adapted to re-examine the properties of the perfect Bose gas in the presence of weak (scaled) non-random potentials, for which we establish similar results. In addition some of our results can be applied to models with diagonal interactions, that is, models which conserve the occupation density in each single particle eigenstate.     

Long Range Correlations and Phase Transitions in Non-equilibrium Diffusive Systems

We obtain explicit expressions for the long range correlations in the ABC model and in diffusive models conditioned to produce an atypical current of particles. In both cases, the two-point correlation functions allow one to detect the occurrence of a phase transition as they become singular when the system approaches the transition.     

Measurements of cavitation bubble dynamics based on a beam-deflection probe

We present an optodynamic measurement of a laser-induced cavitation bubble and its oscillations based on a scanning technique using a laser beam-deflection probe. The deflection of the beam was detected with a fast quadrant photodiode which was built into the optical probe. The applied experimental setup enabled us to carry out one- or two-dimensional scanning of the cavitation bubble, automatic control of the experiment, data acquisition and data processing. Shadow photography was used as a comparative method during the experiments.     

Measurements and analyses of infrasound noise field in the atmosphere

Methods for measuring and analyzing the infrasound noise field inthe atmosphere have been expounded.A set of space correlation radii of noisecorresponding to wind speed 4m/s has been obtained,which can be takenas the tentative basis for an acoustical array design.At the same time,thewind speed-sound pressure relation curves have been measured and calcu-lated,and the anti-jamming ability of the array receiving infrasonic signals isobtained.     

On the Orthocomplementation of State–Property–Systems of Contextual Systems

We adopt an operational approach to quantum mechanics in which a physical system is defined by the mathematical structure of its set of states and properties. We present a model in which the maximal change of state of the system due to interaction with the measurement context is controlled by a parameter which corresponds with the number N of possible outcomes in an experiment. In the case N=2 the system reduces to a model for the spin measurements on a quantum spin-1/2 particle. In the limit N→∞ the system is classical, i.e. the experiments are deterministic and its set of properties is a Boolean lattice. For intermediate situations the change of state due to measurement is neither ‘maximal’ (i.e. quantum) nor ‘zero’ (i.e. classical). We show that two of the axioms used in Piron’s representation theorem for quantum mechanics are violated, namely the covering law and weak modularity. Next, we discuss a modified version of the model for which it is even impossible to define an orthocomplementation on the set of properties. Another interesting feature for the intermediate situations of this model is that the probability of a state transition in general not only depends on the two states involved, but also on the measurement context which induces the state transition.     

Fidelity of Two-Particle Wave Packets Moving around the Schwarzschild Spacetime

Fidelity for two-particle wave packets of spin- particles moving around the Schwarzschild spacetime is discussed. Both acceleration and gravity cause to produce a Wigner rotation that transforms the wave packet as it moves along a specified path in the gravitational field. For considered circular paths, the fidelity between the spin parts of initial and final states of the system, called the spin fidelity, is obtained as a function of angular velocity, elapsed proper time and radius of circular paths. For fixed elapsed proper time and angular momentum of the centroid, there always exists one circular orbit with determined radius on which the fidelity of spin parts is minimum. Using a numerical approach, the behavior of the spin fidelity in terms of the angular velocity, as well as the radius of paths is described for both the spin singlet and spin triplet states.     

Vacuum Fluctuations and Motion of a Charged Test Particle in a Cylindrical Spacetime

The effects of quantum electromagnetic fluctuations upon the motion of a test charged particle are examined in a cylindrical spacetime in which one spatial is compactified. The mean squared fluctuations in the velocity and position of the test particle are calculated. It is found that the random motion of the test particle will be anisotropic. The possible consequences for theories with extra compactified spatial dimensions are discussed.     

Dynamic characterization of charge transport in organic and polymer transistors

In this paper we describe three methods that can be used to measure the transient response of organic and polymer field-effect transistors (FETs) and also how such measurements can be used to determine the drift mobility and velocity. The first method measures the response of a FET to a step voltage applied to the source with the gate grounded and the drain held at close to ground, while the second uses a ramp input to the source. The third technique evaluates the frequency response of the FET, connected as a diode, to a large-signal alternating voltage. We show that important information can be obtained from such measurements which can be quantitatively interpreted with the help of models that we are developing. In general, there is good agreement between the drift mobility measured with these approaches and the field-effect mobility calculated from transistor output and transfer characteristics. The specific results we present in this paper are for pentacene devices; however, other recent work by our group indicates that these results are more general.     

Low-Temperature Dynamics of the Curie-Weiss Model: Periodic Orbits,Multiple Histories,and Loss of Gibbsianness

We consider the Curie-Weiss model at initial temperature 0<β ⁻¹≤∞ in vanishing external field evolving under a Glauber spin-flip dynamics with temperature 0<β′⁻¹≤∞. We study the limiting conditional probabilities and their continuity properties and discuss their set of points of discontinuity (bad points). We provide a complete analysis of the transition between Gibbsian and non-Gibbsian behavior as a function of time, extending earlier work for the case of independent spin-flip dynamics.     

Reconciling Spacetime and the Quantum: Relational Blockworld and the Quantum Liar Paradox

The Relational Blockworld (RBW) interpretation of non-relativistic quantum mechanics (NRQM) is introduced. Accordingly, the spacetime of NRQM is a relational, non-separable blockworld whereby spatial distance is only defined between interacting trans-temporal objects. RBW is shown to provide a novel statistical interpretation of the wavefunction that deflates the measurement problem, as well as a geometric account of quantum entanglement and non-separability that satisfies locality per special relativity and is free of interpretative mystery. We present RBW’s acausal and adynamical resolution of the so-called “quantum liar paradox,” an experimental set-up alleged to be problematic for a spacetime conception of reality, and conclude by speculating on RBW’s implications for quantum gravity.     

Parametrization of Projector-Based Witnesses for Bipartite Systems

Entanglement witnesses are nonpositive Hermitian operators which can detect the presence of entanglement. In this paper, we provide a general parametrization for orthonormal basis of ℂ ⁿ and use it to construct projector-based witness operators for entanglement detection in the vicinity of pure bipartite states. Our method to parameterize entanglement witnesses is operationally simple and could be used for doing symbolic and numerical calculations. As an example we use the method for detecting entanglement between an atom and the single mode of quantized field, described by the Jaynes-Cummings model. We also compare the detection of witnesses with the negativity of the state, and show that in the vicinity of pure stats such constructed witnesses able to detect entanglement of the state.     

Coexistence of Ordered and Disordered Phases in Potts Models in the Continuum

This is the second of two papers on a continuum version of the Potts model, where particles are points in ℝ ^d , d≥2, with a spin which may take S≥3 possible values. Particles with different spins repel each other via a Kac pair potential of range γ ⁻¹, γ>0. In this paper we prove phase transition, namely we prove that if the scaling parameter of the Kac potential is suitably small, given any temperature there is a value of the chemical potential such that at the given temperature and chemical potential there exist S+1 mutually distinct DLR measures.     

Fidelity for States of Spin- \frac{1}{2} Particles Moving in a Traversable Wormhole Spacetime

Fidelity for states of spin- particles moving in a static spherically symmetric traversable wormhole spacetime is discussed. When the centroid of the corresponding wave packet moves along a specified path in the gravitational field, both acceleration and gravity cause to transform the state of the particle. For circular orbits of the centroid coinciding the throat of wormhole, the fidelity between initial and final states of the whole system as well as the fidelity of the spin parts of the states are equal to the unity. This means that, the error in quantum communication diminishes on such a paths. For fixed elapsed proper time and angular momentum of the centroid, there always exists one circular orbit with determined radius on which the fidelity of spin parts is minimum. The fidelity for wave packets moving along a radial geodesic toward the throat of wormhole is also discussed. In this case, the centroid traverses the wormhole and reaches to the other side, with a perfect fidelity for the spin parts, though the fidelity for the states of the whole system is not perfect.     

Tri-meson mixing of π–η–η′ and ρ–ω–φ in the light-cone quark model

The radiative transition form factors of the pseudoscalar mesons π, η, η′ and the vector mesons ρ, ω, φ are restudied with π–η–η′ and ρ–ω–φ in the tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson mixing than previous results in a two-mixing-angle scenario of only two-meson η–η′ mixing and ω–φ mixing.