Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session D33: Focus Session: Quantum Foundations II |
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Sponsoring Units: GQI Chair: Steven Flammia, University of New Mexico Room: Colorado Convention Center 403 |
Monday, March 5, 2007 2:30PM - 2:42PM |
D33.00001: Adiabaticity in Open Quantum Systems Daniel Lidar, Marcelo Sarandy The adiabatic approximation is an 80+ year old pillar of quantum mechanics, which has found rich applications in a variety of physics and chemistry problems. However, in its original formulation the adiabatic theorem was derived in the context of closed quantum systems, described by unitary dynamics. We have recently introduced a generalization of the the adiabatic theorem to open quantum systems described by convolutionless master equations [1]. This version of the adiabatic theorem is naturally suited to problems in quantum information theory, and we describe applications to the adiabatic quantum computing paradigm [2], and to the problem of geometric phases (both Abelian and non-Abelian) in open quantum systems undergoing cyclic adiabatic evolution [3]. One of our main findings is that, in general, adiabaticity in an open quantum system depends on two competing timescales: the speed of the driving field and the decoherence due to the interaction with the environment. These timescales generically determine a finite interval for adiabaticity. This has implications for both adiabatic quantum computing and the robustness of geometric phases to decoherence. \newline \newline [1] M.S. Sarandy and D.A. Lidar, PRA 71, 012331 (2005). \newline [2] M.S.S. and D.A.L., PRL 95, 250503 (2005). \newline [3] M.S.S. and D.A.L., PRA 73, 062101 (2006). [Preview Abstract] |
Monday, March 5, 2007 2:42PM - 2:54PM |
D33.00002: Quantum Erasure and Nonlocality in Electronic Mach-Zehnder Interferometers Kicheon Kang We propose a possible realization of solid-state quantum eraser in which electrons are injected into a mesoscopic conductor in the quantum Hall regime [1]. The conductor is composed of a two-path interferometer, an electronic analog of the optical Mach-Zehnder interferometer, and a quantum point contact detector electrostatically coupled to the interferometer. The Coulomb interaction between the interferometer and the detector induces a phase shift that enables the entanglement and the {\it which-path} detection. While the interference of the average output current at the interferometer is suppressed by the which-path information, the which-path information is erased and the hidden coherence reappears in the cross-correlation measurement between the interferometer and the detector output leads. We also investigate a modified setup in which the detector is replaced by a two-path interferometer. We show that the distinguishability of the path and the visibility of joint detection can be controlled in a continuous manner and satisfy a complementarity relation for the entangled electrons. Further, we show that this geometry can be used to test the Bell's inequality. [1] K. Kang, quant-ph/0607031. [Preview Abstract] |
Monday, March 5, 2007 2:54PM - 3:06PM |
D33.00003: Lyapunov Generation of Entanglement and the Correspondence Principle Cyril Petitjean, Philippe Jacquod We show how a classically vanishing interaction generates entanglement between two initially nonentangled particles, without affecting their classical dynamics. For chaotic dynamics, the rate of entanglement is shown to saturate at the Lyapunov exponent of the classical dynamics as the interaction strength increases. In the saturation regime, the one-particle Wigner function follows classical dynamics better and better as one goes deeper and deeper in the semiclassical limit. This demonstrates that quantum-classical correspondence at the microscopic level does not require coupling to a large number of external degrees of freedom. [Preview Abstract] |
Monday, March 5, 2007 3:06PM - 3:18PM |
D33.00004: Time-Symmetric Quantum Mechanics K.B. Wharton The standard Copenhagen Interpretation of quantum mechanics (QM) is not time-symmetric. For example, the collapse postulate applies only in the forward time direction. But this is merely an asymmetry of the interpretation, not QM itself, which is as time-symmetric as the boundary conditions on the system (1). This motivates the search for an interpretation that consistently explains both a forward-time and reversed-time perspective of the same physical events. I present soon-to-be-published results (2) demonstrating that it is possible to have such an interpretation of non-relativistic QM. This is accomplished by applying two consecutive boundary conditions onto solutions of a time-symmetric wave equation. The results appear to match standard QM, but do so without requiring a time-asymmetric discontinuity upon measurement, thereby realigning QM with an important fundamental symmetry. I will also discuss the application of this technique to the Klein-Gordon wave equation. \\ (1) Y. Aharonov, P. Bergmann, and J. Lebovitz, ``Time symmetry in the quantum process of measurement,'' \textit{Phys. Rev.} \textbf{134}, B1410 (1964). (2) K. B. Wharton, ``Time-Symmetric Quantum Mechanics'', accepted for publication in \textit{Foundations of Physics} \textbf{37} (2007). [Preview Abstract] |
Monday, March 5, 2007 3:18PM - 3:30PM |
D33.00005: Decoherence and the Uncertainty Principle: Theory David Craig, Adam Lemke We investigate the relation between decoherence and the uncertainty principle, both analytically and numerically, in some simple models of quantum measurement. In consistent histories formulations of quantum theory, probabilities may be consistently assigned only in sets of histories which decohere, i.e. in sets in which the interference among the various branches vanishes. Measurements may thus in part be construed as local processes which serve to destroy interference. We study the extent to which the uncertainty principle may be interpreted as the failure of measurements of non- commuting observables to lead to decohering branches in some simple quantum measurement models in the context of a general framework for consistent histories quantum theories due to Hartle known as generalized quantum theory. [Preview Abstract] |
Monday, March 5, 2007 3:30PM - 3:42PM |
D33.00006: Decoherence and the Uncertainty Principle: Numerics Adam Lemke, David Craig We investigate the relation between decoherence and the uncertainty principle, both analytically and numerically, in some simple models of quantum measurement. In consistent histories formulations of quantum theory, probabilities may be consistently assigned only in sets of histories which decohere, i.e. in sets in which the interference among the various branches vanishes. Measurements may thus in part be construed as local processes which serve to destroy interference. We study numerically the extent to which the uncertainty principle may be interpreted as the failure of measurements of non-commuting observables to lead to decohering branches in some simple quantum measurement models. [Preview Abstract] |
Monday, March 5, 2007 3:42PM - 3:54PM |
D33.00007: Quantum Young's experiment, nonlocality and trajectories Edward R. Floyd The trajectory representation of Young's diffraction experiment is developed for a quantum particle. The double slit problem is idealized by simplifying each slit by a point source. The correlated point sources induce a self-entanglement in $\psi$ of the synthesized quantum particle. In turn, entanglement induces nonlocality. A composite reduced action (a generator of nonlocal motion) for the self entangled $\psi$ is developed. Contours of reduced action and nonlocal trajectories are generated in the region near the two point sources. The nonlocal trajectory through any point in configuration space also goes through both point sources simultaneously. [Preview Abstract] |
Monday, March 5, 2007 3:54PM - 4:06PM |
D33.00008: Phase-Covariant Cloning and EPR Correlations in Entangled Macroscopic Quantum Systems Francesco De Martini, Fabio Sciarrino Theoretical and experimental results on the Quantum Injected Optical Parametric Amplification (QI-OPA) of optical qubits in the high gain regime are reported. The large size of the gain parameter in the collinear configuration, g = 4.5, allows the generation of EPR nonlocally correlated bunches containing about 4000 photons. The entanglement of the related Schroedinger Cat-State (SCS) is demonstrated as well as the establishment of Phase-Covariant quantum cloning. The cloning ``fidelity'' has been found to match the theoretical results. According to the original 1935 definition of the SCS, the overall apparatus establishes for the first time the nonlocal correlations between a microcopic spin (qubit) and a high J angular momentum i.e. a mesoscopic multiparticle system close to the classical limit. The results of the first experimental realization of the Herbert proposal for superluminal communication via nonlocality will be presented. [Preview Abstract] |
Monday, March 5, 2007 4:06PM - 4:18PM |
D33.00009: A Local de-Broglie Bohm interpretation of entanglement Michael Clover We present a local interpretation of the de Broglie-Bohm (pilot wave) trajectory prescription for entangled singlet states of massive particles and show that by using appropriately retarded wavefunctions, this local model will exceed Bell's inequality, making no appeal to any detector inefficiencies. We then analyze a possible experimental configuration appropriate to massive two-particle singlet wavefunctions and find that as long as the particles are not ultra-relativistic, the Dirac wave(s) can propagate from Alice or Bob's changing magnetic field, through space to the other detector before the particle arrives, allowing our local interpretation of the two-particle entangled trajectories. The same analysis suggests a physical mechanism that can actually throw away events and create a detector loophole. [Preview Abstract] |
Monday, March 5, 2007 4:18PM - 4:30PM |
D33.00010: The Fabrication of de Broglie Wave J.X. Zheng-Johansson, P.-I. Johansson If an electron e$^{\mbox{-}}$ of de Broglie wavelength ${\mit {\Lambda}}_d$ is fired at $A$ into a field-free chamber of size $AB>>{\mit{\Lambda}}_d$, then, it is a classical point particle. We will be able to register its position, e.g. $B$, and time $T$. If at $B$ is a diffraction grating of spacing $\sim {\mit{\Lambda}}_d$, then the e$^{\mbox{-}}$ arriving in it is a quantum particle and produces diffraction patterns; e$^ {\mbox{-}}$ must be a train of traveling plane wave of many ${\mit{\Lambda}}_d$'s. Naturally a viable theory for the formation of basic particles, like the electron, ought to pass among others the above simple but critical test: being a particle and wave. One may illustrate the former feature by a wave packet which yet lacks periodicity in space-time of a plane wave. We recently developed [1-3] based on overall experiments a particle formation scheme. By it a basic particle like the electron is made of a massless oscillatory charge $-e$ or $+e$ of a fixed oscillatory energy, and the resulting electromagnetic waves. When the particle is in motion, so is its source charge, then owing to the resulting Doppler effect the EM wave evolves into a beat wave resembling precisely a traveling de Broglie wave. It firstly passes the above test well, it obeys de Broglie relations and Schr\"odinger equation, and it has the overall other observational particle properties. \ Refs: JXZJ \& PIJ in 1. {\it Unif. of Clas., Quant. \& Rel. Mech. \& Four Forces}, Nova Sci. 2005, Fwd R Lundin; 2. {\it Quant. Theory \& Symm. IV}, ed V Debrev, Heron Press, 2006, 763; 771; 3. {\it Prog. in Phys.} {\bf 4}, 32, 2006; refs therein. [Preview Abstract] |
Monday, March 5, 2007 4:30PM - 4:42PM |
D33.00011: Replacing The General Covariance In the SM Dirac Equation Gauge Derivatives With An Equivalent General Covariance In The Metric That This Dirac Equation is Derived From Joel Maker We replace the general covariance in the gauge derivatives in the Standard Model (SM) with a general covariance in the\textit{ original} metric that is used to start the derivation of the SM Dirac equation. This puts in the general covariance at the very beginning of the Dirac equation derivation, \textit{where it belongs}. The result is a new Dirac equation ($\surd $\textbf{\textit{g}}$_{\mu \mu }$\textit{$\gamma $}$_{\mu }$\textit{$\partial \psi $/$\partial $x}$_{\mu }$\textit{+i$\omega \psi $=0 }with\textbf{~}\textbf{g}$_{oo}$=1-2e$^{2}$/rm$_{e}$c$^{2})$ that does not require the covariant gauge derivatives anymore but yet still \textit{retains }the general covariance creating a \textbf{ONE} free parameter theory, instead of 18 of the SM. For example this new Dirac equation has a singularity-stability radius r$_{H}$ and, because of equivalence principle considerations, is allowed only \textit{one} type of charge e. Thus near r$_{H}$ the 2P$_{3/2}$ state for this new Dirac equation gives a $\psi ^{tt}\psi $ azimuthal trifolium, 3 lobe shape; so this ONE charge e (so don't need \textbf{ color} to guarantee this) spends \textbf{1/3} of its time in each lobe (\textbf{fractionally charged} lobes), the lobe structure is locked into the center of mass \textbf{(asymptotic freedom}), there are\textbf{ six} 2P states (corresponding to the 6 flavors) ;~ which are the~~\textbf{main properties of quarks}!~ Thus we end up with the experimental implications of the Standard Model (SM) by postulating just ONE particle with mass. [Preview Abstract] |
Monday, March 5, 2007 4:42PM - 4:54PM |
D33.00012: Purple bacteria and quantum Fourier transform Samir Lipovaca The LH-II of purple bacteria Rhodospirillum (Rs.) molischianum and Rhodopseudomonas (Rps.) acidophila adopts a highly symmetrical ring shape, with a radius of about 7 nm. In the case of Rps. acidophila the ring has a ninefold symmetry axis, and in LH-II from Rs. molischianum the ring has an eightfold symmetry axis. These rings are found to exibit two bands of excitons. A simplified mathematical description of the exciton states is given in Hu, X. {\&} Schulten, K. (1997) Physics Today 50, 28-34. Using this description, we will show, by suitable labeling of the lowest energy (Qy) excited states of individual BChls, that the resulting exciton states are the quantum Fourier transform of the BChls excited states. For Rs. molischianum ring exciton states will be modeled as the four qubit quantum Fourier transform and the explicit circuit will be derived. Exciton states for Rps. acidophila ring cannot be modeled with an integer number of qubits. Both quantum Fourier transforms are instances of the hidden subgroup problem and this opens up a possibility that both purple bacteria implement an efficient quantum circuit for light harvesting. [Preview Abstract] |
Monday, March 5, 2007 4:54PM - 5:06PM |
D33.00013: The Mystery of Genetic Tape Shantilal Goradia I attempt to explain information exchanges of a DNA at particle level at Planck scale in terms of the quantum computer theory. The substitution of Euclidean wormholes proposed by Hawking in hep-th/0507171, in Fig 2 of my gr-qc/0507130 [1] makes them unstable, giving them the ability to register alternate bits of information, OPEN or CLOSE, every other natural unit of Planck time with time dependent sequencing. I will present a pictorial view, of my idea introduced at Feynman Festival Aug, 2006 and DNP06. Whether the wormholes are Euclidean and therefore inherently unstable, or they are Lorentzian and destabilized by quantum fluctuations of gravity, reported degrading with time [2] is of secondary importance. The point is that the instability of wormholes explains cellular communications, in addition to running couplings explained in more detail in physics/0210040. The quantum mouths proposed in [1] can cross the cell membrane and cell wall to express their information. Nature creates the instability to generate qubits of information, for storage and expression of heredity. Nature burns no encyclopedia. [1] Goradia S. G., \textit{Indian Journal of Theoretical Physics,} \textbf{52} 143 (2004) [2] Leslie J., \textit{Physical Cosmology and Philosophy,} 90 (1990) [Preview Abstract] |
Monday, March 5, 2007 5:06PM - 5:18PM |
D33.00014: Do Particles have Barcodes? Shantilal Goradia If an elementary particle shown in Fig 2 of gr-qc/0507130 has an UNSTABLE quantum connection to the rest of the universe calibrated by nature in terms of Planck times, as also proposed in my separate MAR07 abstract, there exists a possibility that each particle has a barcode of its own. Instability implies varying periods of connections and disconnections of particles to the universe, which would be equivalent to the varying widths of white and black strips of commercial barcodes. Considering the high order of magnitude of Planck times in a second, each particle and the universe generated by its radiations may have their unique birth times registered in their barcodes. My quest for the cause of consciousness, in MAR06 abstracts, as an additional implication of physics/0210040, leads to the inquiry if these unique parallel universes are like the ones that give rise to consciousness as proposed by some physicists. With all due respect, the attempts to explain TOE of inert matter may not be attempts to explain one step to climb up on a stairway at a time. They may be attempts to explain only half a step at a time to on a stairway made with only integer number of steps. The search for TOE assumes such a theory exists. Mathematics has no barrels to fire bullets that can shoot down a non-existent bird. A Hamiltonian knows no consciousness, a missing ingredient of biology made of particles or vice versa, and of realistic TOE. [Preview Abstract] |
Monday, March 5, 2007 5:18PM - 5:30PM |
D33.00015: More on Atonic Mechanics Alfred Phillips We have shown that crystal based experiments, such as those of Davisson and Germer, do not empirically verify de Broglie's matter-wave hypothesis. We named this theory Atonic Mechanics. This mechanics has also been used to accurately calculate the hundreds of helium atom energy levels tabulated by NIST. We have joined Atonic Mechanics with Einstein's General Relativity. Now we show how fractional values of h-bar arise for the angular momentum of the helium atom in this theory. We now also discuss energy and momentum in Atonic Mechanics. [Preview Abstract] |
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