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Articles 1 - 17 of 17

Full-Text Articles in Quantum Physics

Decoherence And Recoherence In A Vibrating Rf Squid, Eyal Buks, M. P. Blencowe Nov 2006

Decoherence And Recoherence In A Vibrating Rf Squid, Eyal Buks, M. P. Blencowe

Dartmouth Scholarship

We study an rf SQUID, in which a section of the loop is a freely suspended beam that is allowed to oscillate mechanically. The coupling between the rf SQUID and the mechanical resonator originates from the dependence of the total magnetic flux threading the loop on the displacement of the resonator. Motion of the latter affects the visibility of Rabi oscillations between the two lowest energy states of the rf SQUID. We address the feasibility of experimental observation of decoherence and recoherence, namely decay and rise of the visibility, in such a system.


Energy In Vectorial Relativity: E ≈ M.C2, Jorge A. Franco Nov 2006

Energy In Vectorial Relativity: E ≈ M.C2, Jorge A. Franco

Jorge A Franco

In previous work it was shown that assumptions, y = y' and z = z’, within Lorentz Transformations were needless, and therefore groundless. Because of such assumptions, Lorentz Transformations (LT) depend on the body’s spatial orientation, i.e. the well-known transverse and longitudinal transformations of magnitudes, characterized by different scaling factors. On the contrary, the development of LT without assumptions, brought about new transformations that do not depend on spatial orientation and a unique mass definition, m = °m /[1 –(v/c)^2]^(3/2). As it is known, Einstein arrived at two definitions: transverse mass mT = °m /[1 –(v/c)^2]^ (1/2) and longitudinal mass …


Casimir Forces And Non-Newtonian Gravitation, Roberto Onofrio Oct 2006

Casimir Forces And Non-Newtonian Gravitation, Roberto Onofrio

Dartmouth Scholarship

The search for non-relativistic deviations from Newtonian gravitation can lead to new phenomena signalling the unification of gravity with the other fundamental interactions. Various recent theoretical frameworks indicate a possible window for non-Newtonian forces with gravitational coupling strength in the micrometre range. The major expected background in the same range is attributable to the Casimir force or variants of it if dielectric materials, rather than conducting ones, are considered. Here we review the measurements of the Casimir force performed so far in the micrometre range and how they determine constraints on non-Newtonian gravitation, also discussing the dominant sources of false …


Generalized Entanglement As A Natural Framework For Exploring Quantum Chaos, Y. S. Weinstein, L Viola Oct 2006

Generalized Entanglement As A Natural Framework For Exploring Quantum Chaos, Y. S. Weinstein, L Viola

Dartmouth Scholarship

We demonstrate that generalized entanglement (Barnum et al., Phys. Rev. A, 68 (2003) 032308) provides a natural and reliable indicator of quantum chaotic behavior. Since generalized entanglement depends directly on a choice of preferred observables, exploring how generalized entanglement increases under dynamical evolution is possible without invoking an auxiliary coupled system or decomposing the system into arbitrary subsystems. We find that, in the chaotic regime, the long-time saturation value of generalized entanglement agrees with random matrix theory predictions. For our system, we provide physical intuition into generalized entanglement within a single system by invoking the notion of extent …


Enhanced Convergence And Robust Performance Of Randomized Dynamical Decoupling, Lea F. Santos, Lorenza Viola Oct 2006

Enhanced Convergence And Robust Performance Of Randomized Dynamical Decoupling, Lea F. Santos, Lorenza Viola

Dartmouth Scholarship

We demonstrate the advantages of randomization in coherent quantum dynamical control. For systems which are either time-varying or require decoupling cycles involving a large number of operations, we find that simple randomized protocols offer superior convergence and stability as compared to deterministic counterparts. In addition, we show how randomization may allow us to outperform purely deterministic schemes at long times, including combinatorial and concatenated methods. General criteria for optimally interpolating between deterministic and stochastic design are proposed and illustrated in explicit decoupling scenarios relevant to quantum information storage.


Exact Casimir Interaction Between Eccentric Cylinders, D. A. R. Dalvit, F. C. Lombardo, F. D. Mazzitelli, R. Onofrio Aug 2006

Exact Casimir Interaction Between Eccentric Cylinders, D. A. R. Dalvit, F. C. Lombardo, F. D. Mazzitelli, R. Onofrio

Dartmouth Scholarship

The Casimir force is the ultimate background in ongoing searches for extragravitational forces in the micrometer range. Eccentric cylinders offer favorable experimental conditions for such measurements as spurious gravitational and electrostatic effects can be minimized. Here we report on the evaluation of the exact Casimir interaction between perfectly conducting eccentric cylinders using a mode summation technique, and study different limiting cases of relevance for Casimir force measurements, with potential implications for the understanding of mechanical properties of nanotubes.


Investigating How Students Think About And Learn Quantum Physics: An Example From Tunneling, Jeffrey Todd Morgan May 2006

Investigating How Students Think About And Learn Quantum Physics: An Example From Tunneling, Jeffrey Todd Morgan

Electronic Theses and Dissertations

Much of physics education research (PER) has focused on introductory courses and topics, with less research done into how students learn physics in advanced courses. Members of The University of Maine Physics Education Research Laboratory (PERL) have begun studying how students in advanced physics courses reason about classical mechanics, thermal physics, and quantum physics. Here, we describe an investigation into how students reason about quantum mechanical tunneling, and detail how those findings informed a portion of a curriculum development project. Quantum mechanical tunneling is a standard topic discussed in most modern physics and quantum physics courses. Understanding tunneling is crucial …


Energy Landscape Of D -Dimensional Q -Balls, Marcelo Gleiser, Joel Thorarinson Mar 2006

Energy Landscape Of D -Dimensional Q -Balls, Marcelo Gleiser, Joel Thorarinson

Dartmouth Scholarship

We investigate the properties of Q-balls in d spatial dimensions. First, a generalized virial relation for these objects is obtained. We then focus on potentials V(ϕϕ†)=∑3n=1an(ϕϕ†)n, where an is a constant and n is an integer, obtaining variational estimates for their energies for arbitrary charge Q. These analytical estimates are contrasted with numerical results and their accuracy evaluated. Based on the results, we offer a simple criterion to classify large and small d-dimensional Q-balls for this class of potentials. A minimum charge is then computed and its dependence on spatial dimensionality is shown to scale as Qmin∼exp(d). We also briefly …


Bound States In The Continuum In Quantum-Dot Pairs, Gonzalo Ordonez, Kyungsun Na, Sungyun Kim Jan 2006

Bound States In The Continuum In Quantum-Dot Pairs, Gonzalo Ordonez, Kyungsun Na, Sungyun Kim

Scholarship and Professional Work - LAS

It is shown that for two open quantum dots connected by a wire, “bound states in the continuum” of a single electron are formed at nearly periodic distances between the dots. This is due to Fabry-Pérot interference between quasibound states in each dot. The bound states are nonlocal, describing the electron trapped in both dots at the same time. Theoretical and numerical results show that trapped states exist even if the wire connecting the dots is relatively long.


Quantum Dynamics As An Analog Of Conditional Probability, Matthew S. Leifer Jan 2006

Quantum Dynamics As An Analog Of Conditional Probability, Matthew S. Leifer

Mathematics, Physics, and Computer Science Faculty Articles and Research

Quantum theory can be regarded as a noncommutative generalization of classical probability. From this point of view, one expects quantum dynamics to be analogous to classical conditional probabilities. In this paper, a variant of the well-known isomorphism between completely positive maps and bipartite density operators is derived, which makes this connection much more explicit. This isomorphism is given an operational interpretation in terms of statistical correlations between ensemble preparation procedures and outcomes of measurements. Finally, the isomorphism is applied to elucidate the connection between no-cloning and no-broadcasting theorems and the monogamy of entanglement, and a simplified proof of the no-broadcasting …


Conditional Density Operators And The Subjectivity Of Quantum Operations, Matthew S. Leifer Jan 2006

Conditional Density Operators And The Subjectivity Of Quantum Operations, Matthew S. Leifer

Mathematics, Physics, and Computer Science Faculty Articles and Research

Assuming that quantum states, including pure states, represent subjective degrees of belief rather than objective properties of systems, the question of what other elements of the quantum formalism must also be taken as subjective is addressed. In particular, we ask this of the dynamical aspects of the formalism, such as Hamiltonians and unitary operators. Whilst some operations, such as the update maps corresponding to a complete projective measurement, must be subjective, the situation is not so clear in other cases. Here, it is argued that all trace preserving completely positive maps, including unitary operators, should be regarded as subjective, in …


Electron Scattering From High-Momentum Neutrons In Deuterium, A.V. Klimenko, S. E. Kuhn, H. Bagdasaryan, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, Gail Dodge, G. Gavalian, N. Guler, C.E. Hyde-Wright, A. Klein, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, Et Al., Clas Collaboration Jan 2006

Electron Scattering From High-Momentum Neutrons In Deuterium, A.V. Klimenko, S. E. Kuhn, H. Bagdasaryan, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, Gail Dodge, G. Gavalian, N. Guler, C.E. Hyde-Wright, A. Klein, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, Et Al., Clas Collaboration

Physics Faculty Publications

We report results from an experiment measuring the semiinclusive reaction 2H(e,e′ps) in which the proton ps is moving at a large angle relative to the momentum transfer. If we assume that the proton was a spectator to the reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred. This method, known as spectator tagging, can be used to study electron scattering from high-momentum (off-shell) neutrons in deuterium. The data were taken with a 5.765 GeV electron beam on a deuterium target in Jefferson Laboratory's Hall B, using the CEBAF …


Erratum: Η' Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev (Phys. Rev. Lett. 96, Pg 062001, 2006), H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, Et Al., Clas Collaboration Jan 2006

Erratum: Η' Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev (Phys. Rev. Lett. 96, Pg 062001, 2006), H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, Et Al., Clas Collaboration

Physics Faculty Publications

No abstract provided.


Differential Cross Sections For 𝛾 + P → K⁺ + Y For Λ And Σ⁰ Hyperons, H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, S. Bültmann, G. E. Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. V. Klimenko, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., Clas Collaboration Jan 2006

Differential Cross Sections For 𝛾 + P → K⁺ + Y For Λ And Σ⁰ Hyperons, H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, S. Bültmann, G. E. Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. V. Klimenko, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

High-statistics cross sections for the reactions 𝛾 + p → K⁺ + Λ and 𝛾 + p → K⁺ + Σ⁰ have been measured using CLAS at Jefferson Lab for center-of-mass energies W between 1.6 and 2.53 GeV, and for -0.85 < cos θ Kc.m. < +0.95. In the K⁺ + Λ channel we confirm a resonance-like structure near W=1.9 GeV at backward kaon angles. The position and width of this structure change with angle, indicating that more than one resonance is likely playing a role. The K⁺ + Λ channel at forward angles and all energies is well described by a t-channel scaling characteristic of Regge exchange, whereas the same scaling applied to the K⁺ + Σ⁰ channel is less successful. Several existing theoretical models are compared to the data, but none provide a good representation of the results.


High-Energy Effective Action From Scattering Of Qcd Shock Waves, Ian Balitsky Jan 2006

High-Energy Effective Action From Scattering Of Qcd Shock Waves, Ian Balitsky

Physics Faculty Publications

At high energies, the relevant degrees of freedom are Wilson lines--infinite gauge links ordered along straight lines collinear to the velocities of colliding particles. The effective action for these Wilson lines is determined by the scattering of QCD shock waves. I develop the symmetric expansion of the effective action in powers of strength of one of the shock waves and calculate the leading term of the series. The corresponding first-order effective action, symmetric with respect to projectile and target, includes both up and down fan diagrams and pomeron loops


Η’ Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev, M. Bektasoglu, S.L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, A. V. Klimenko, L. M. Qin, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration Jan 2006

Η’ Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev, M. Bektasoglu, S.L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, A. V. Klimenko, L. M. Qin, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

Differential cross sections for the reaction γp→η′p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data suggest for the first time the coupling of the η′N channel to both the S11(1535) and P11(1710) resonances, known to couple strongly to the ηN channel in photoproduction on the proton, and the importance of J=3/2 resonances in the process.


Measurement Of The Deuteron Structure Function F₂ In The Resonance Region And Evaluation Of Its Moments, H. Bagdasaryan, S. Bültmann, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, S. E. Kuhn, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration Jan 2006

Measurement Of The Deuteron Structure Function F₂ In The Resonance Region And Evaluation Of Its Moments, H. Bagdasaryan, S. Bültmann, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, S. E. Kuhn, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

Inclusive electron scattering off the deuteron has been measured to extract the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement covers the entire resonance region from the quasielastic peak up to the invariant mass of the final-state hadronic system W similar or equal to 2.7 GeV with four-momentum transfers Q2 from 0.4 to 6 (GeV/c)2. These data are complementary to previous measurements of the proton structure function F2 and cover a similar two-dimensional region of Q2 and Bjorken variable x. Determination of …