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  • 1.
    Bernad, Joszef Zsolt
    et al.
    Massey University.
    Jääskeläinen, Markku
    Dalarna University. Institute of Fundamental Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, Massey University, Palmerston North, New Zealand.
    Zulicke, Ulrich
    Massey University.
    Effects of a quantum measurement on the electric conductivity: Application to graphene2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 7, article id 073403Article in journal (Refereed)
    Abstract [en]

    We generalize the standard linear-response (Kubo) theory to obtain the conductivity of a system that is subject to a quantum measurement of the current. Our approach can be used to specifically elucidate how back-action inherent to quantum measurements affects electronic transport. To illustrate the utility of our general formalism, we calculate the frequency-dependent conductivity of graphene and discuss the effect of measurement-induced decoherence on its value in the dc limit. We are able to resolve an ambiguity related to the parametric dependence of the minimal conductivity.

  • 2.
    Dutta, Omjyoti
    et al.
    University of Arizona.
    Jääskeläinen, Markku
    Department of Physics and College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
    Meystre, Pierre
    University of Arizona.
    Polarizing beam splitter for dipolar molecules2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 71, no 5, article id 051601(R)Article in journal (Refereed)
    Abstract [en]

    We propose a coherent beam splitter for polarized heteronuclear molecules based on a stimulated Raman adiabatic passage scheme that uses a tripod linkage of electrotranslational molecular states. We show that for strongly polarized molecules the rotational dynamics imposes significantly larger Rabi frequencies than would otherwise be expected, but within this limitation, a full transfer of the molecules to two counterpropagating ground-state wave packets is possible.

  • 3.
    Dutta, Omjyoti
    et al.
    University of Arizona.
    Jääskeläinen, Markku
    Department of Physics and College of Optical Sciences, The University of Arizona.
    Meystre, Pierre
    University of Arizona.
    Single-mode acceleration of matter waves in circular waveguides2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 2, article id 023609Article in journal (Refereed)
    Abstract [en]

    Ultracold gases in ring geometries hold promise for significant improvements of gyroscopic sensitivity. Recent experiments have realized atomic and molecular storage rings with radii in the centimeter range, sizes whose practical use in inertial sensors requires velocities significantly in excess of typical recoil velocities. We use a combination of analytical and numerical techniques to study the coherent acceleration of matter waves in circular waveguides, with particular emphasis on its impact on single-mode propagation. In the simplest case we find that single-mode propagation is best maintained by the application of time-dependent acceleration force with the temporal profile of a Blackmann pulse. We also assess the impact of classical noise on the acceleration process.

  • 4.
    Dutta, Omjyoti
    et al.
    University of Arizona.
    Jääskeläinen, Markku
    Department of Physics and College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
    Meystre, Pierre
    University of Arizona.
    Thomas-Fermi ground state of dipolar fermions in a circular storage ring2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 73, no 4, article id 043610Article in journal (Refereed)
    Abstract [en]

    Recent developments in the field of ultracold gases has led to the production of degenerate samples of polar molecules. These have large static electric-dipole moments, which in turn causes the molecules to interact strongly. We investigate the interaction of polar particles in waveguide geometries subject to an applied polarizing field. For circular waveguides, tilting the direction of the polarizing field creates a periodic inhomogeneity of the interparticle interaction. We explore the consequences of geometry and interaction for stability of the ground state within the Thomas-Fermi model. Certain combinations of tilt angles and interaction strengths are found to preclude the existence of a stable Thomas-Fermi ground state. The system is shown to exhibit different behavior for quasi-one-dimensional and three-dimensional trapping geometries.

  • 5.
    Jääskeläinen, Markku
    Dalarna University, School of Technology and Business Studies, Physics.
    Gravitational self-localization for spherical masses2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 86, no 5, article id 052105Article in journal (Refereed)
    Abstract [en]

    In this work, I consider the center-of-mass wave function for a homogenous sphere under the influence of the self-interaction due to Newtonian gravity. I solve for the ground state numerically and calculate the average radius as a measure of its size. For small masses, M≲10−17 kg, the radial size is independent of density, and the ground state extends beyond the extent of the sphere. For masses larger than this, the ground state is contained within the sphere and to a good approximation given by the solution for an effective radial harmonic-oscillator potential. This work thus determines the limits of applicability of the point-mass Newton Schrödinger equations for spherical masses. In addition, I calculate the fringe visibility for matter-wave interferometry and find that in the low-mass case, interferometry can in principle be performed, whereas for the latter case, it becomes impossible. Based on this, I discuss this transition as a possible boundary for the quantum-classical crossover, independent of the usually evoked environmental decoherence. The two regimes meet at sphere sizes R≈10−7 m, and the density of the material causes only minor variations in this value.

  • 6.
    Jääskeläinen, Markku
    Dalarna University, School of Technology and Business Studies, Physics.
    The wave function as matter density: ontological assumptions and experimental consequences2015In: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 45, no 6, p. 591-610Article in journal (Refereed)
    Abstract [en]

    The wavefunction is the central mathematical entity of quantum mechanics, but it still lacks a universally accepted interpretation. Much effort is spent on attempts to probe its fundamental nature. Here I investigate the consequences of a matter ontology applied to spherical masses of constant bulk density. The governing equation for the center-of-mass wavefunction is derived and solved numerically. The ground state wavefunctions and resulting matter densities are investigated. A lowering of the density from its bulk value is found for low masses due to increased spatial spreading. A discussion of the possibility to experimentally observe these effects is given and the possible consequences for choosing an ontological interpretation for quantum mechanics are commented upon.

  • 7.
    Jääskeläinen, Markku
    et al.
    Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on the Hudson, Hoboken, New Jersey 07030, USA.
    Jeong, Jaeyoon
    Stevens Institute of Technology.
    Search, Christopher P.
    Stevens Institute of Technology.
    Bifurcations and bistability in cavity-assisted photoassociation of Bose-Einstein-condensed molecules2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 6, article id 063615Article in journal (Refereed)
    Abstract [en]

    We study the photoassociation of Bose-Einstein condensed atoms into molecules using an optical cavity field. The driven cavity field introduces a dynamical degree of freedom into the photoassociation process, whose role in determining the stationary behavior has not previously been considered. The semiclassical stationary solutions for the atom and molecules as well as the intracavity field are found and their stability and scaling properties are determined in terms of experimentally controllable parameters including driving amplitude of the cavity and the nonlinear interactions between atoms and molecules. For weak cavity driving, we find a bifurcation in the atom and molecule number occurs that signals a transition from a stable steady state to nonlinear Rabi oscillations. For a strongly driven cavity, there exists bistability in the atom and molecule number.

  • 8.
    Jääskeläinen, Markku
    et al.
    Dalarna University, School of Technology and Business Studies, Physics.
    Lagerkvist, Andreas
    Dalarna University, School of Technology and Business Studies, Mathematics.
    Why do they not answer and do they really learn?: A case study in analysing student response flows in introductory physics using an audience response system2017In: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 38, no 4, article id 045705Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate teaching with a classroom response system in introductory physics with emphasis on two issues. First, we discuss retention between question rounds and the reasons why students avoid answering the question a second time. A question with declining response rate was followed by a question addressing the student reasons for not answering. We find that there appear to be several reasons for the observed decline, and that the students need to be reminded. We argue that small drops are unimportant as the process appears to work despite the drops. Second, we discuss the dynamics of learning in a concept-sequence in electromagnetism, where a majority of the students, despite poor statistics in a first round, manage to answer a followup question correctly. In addition, we analyse the response times for both situations to connect with research on student reasoning on situations with misconception-like answers. From the combination of the answer flows and response time behaviours we find it plausible that conceptual learning occurred during the discussion phase.

  • 9.
    Jääskeläinen, Markku
    et al.
    Institute of Fundamental Sciences and MacDarmid Institute for Advanced Materials and Nanotechnology, Massey University, Manawatu Campus, Palmerston North, New Zealand.
    Lombard, Marijke
    Massey University.
    Zuelicke, Ulrich
    Massey University.
    Refraction in spacetime2011In: American Journal of Physics, ISSN 0002-9505, E-ISSN 1943-2909, Vol. 79, no 6Article in journal (Refereed)
    Abstract [en]

    Refraction, interference, and diffraction are distinguishing features of wavelike phenomena. Although they are usually associated only with a purely spatial wave-propagation pattern, analogs to interference and diffraction involving the spatio-temporal dynamics of waves in one dimension have been discussed. We complete the triplet of analogies by discussing how spatio-temporal analogs to refraction are exhibited by a quantum particle in one dimension that is scattering off a step barrier. Similarly, birefringence in spacetime occurs for a spin-1/2 particle in a magnetic field.

  • 10.
    Jääskeläinen, Markku
    et al.
    Department of Physics and College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
    Meystre, Pierre
    University of Arizona.
    Coherence dynamics of two-mode condensates in asymmetric potentials2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 73, no 1, article id 013602Article in journal (Refereed)
    Abstract [en]

    Detection of weak forces with an accuracy beyond the standard quantum limit holds promise both for fundamental research and for technological applications. Schemes involving ultracold atoms for such measurements are now considered to be prime candidates for increased sensitivity. In this paper we use a combination of analytical and numerical techniques to investigate the possible subshot-noise estimation of applied force fields through detection of coherence dynamics of Bose-condensed atoms in asymmetric double-well traps. Following a semiclassical description of the system dynamics and fringe visibility, we present numerical simulations of the full quantum dynamics that demonstrate the dynamical production of phase squeezing beyond the standard quantum limit. Nonlinear interactions are found to limit the achievable amount to a finite value determined by the external weak force.

  • 11.
    Jääskeläinen, Markku
    et al.
    Department of Physics and College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
    Meystre, Pierre
    University of Arizona.
    Dynamics of Bose-Einstein condensates in double-well potentials2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 71, no 4, article id 043603Article in journal (Refereed)
    Abstract [en]

    We study the dynamics of Bose-Einstein condensates in symmetric double-well potentials following a sudden change of the potential from the Mott-insulator to the superfluid regime. We introduce a continuum approximation that maps that problem onto the wave-packet dynamics of a particle in an anharmonic effective potential. For repulsive two-body interactions the visibility of interference fringes that result from the superposition of the two condensates following a stage of ballistic expansion exhibits a collapse of coherent oscillations onto a background value whose magnitude depends on the amount of squeezing of the initial state. Strong attractive interactions are found to stabilize the relative number dynamics. We visualize the dynamics of the system in phase space using a quasiprobability distribution that allows for an intuitive interpretation of the various types of dynamics.

  • 12.
    Jääskeläinen, Markku
    et al.
    Laser Physics and Quantum Optics, Royal Institute of Technology, Roslagstullsbacken 21 SE-10691 Stockholm, Sweden.
    Stenholm, Stig
    echnology, Roslagstullsbacken 21 SE-10691 Stockholm, Sweden.
    Adiabatic propagation in potential structures2002In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 66, no 2, article id 023608Article in journal (Refereed)
    Abstract [en]

    In this work the adiabatic approximation is applied to the propagation of matter waves in confined geometries like those experimentally realized in recent atom optical experiments. Adiabatic propagation along a channel is assumed not to mix the various transverse modes. Nonadiabatic corrections arise from the potential squeezing and bending. Here we investigate the effect of the former. Detailed calculations of two-dimensional propagation are carried out both exactly and in an adiabatic approximation. This offers the possibility to analyze the validity of adiabaticity criteria. A semiclassical (sc) approach, based on the sc Massey parameter is shown to be inadequate, and the diffraction due to wave effects must be included separately. This brings in the Fresnel parameter well known from optical systems. Using these two parameters, we have an adequate understanding of adiabaticity on the system analyzed. Thus quantum adiabaticity must also take cognizance of the intrinsic diffraction of matter waves.

  • 13.
    Jääskeläinen, Markku
    et al.
    Kungliga tekniska högskolan.
    Stenholm, Stig
    Kungliga tekniska högskolan.
    Localization in splitting of matter waves2003In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 68, no 3, article id 033607Article in journal (Refereed)
    Abstract [en]

    In this paper we present an analysis of how matter waves, guided as propagating modes in potential structures, are split under adiabatic conditions. The description is formulated in terms of localized states obtained through a unitary transformation acting on the mode functions. The mathematical framework results in coupled propagation equations that are decoupled in the asymptotic regions as well before as after the split. The resulting states have the advantage of describing propagation in situations, for instance matter-wave interferometers, where local perturbations make the transverse modes of the guiding potential unsuitable as a basis. The different regimes of validity of adiabatic propagation schemes based on localized versus delocalized basis states are also outlined. Nontrivial dynamics for superposition states propagating through split potential structures is investigated through numerical simulations. For superposition states the influence of longitudinal wave-packet extension on the localization is investigated and shown to be accurately described in quantitative terms using the adiabatic formulations presented here.

  • 14. Jääskeläinen, Markku
    et al.
    Stenholm, Stig
    Laser Physics and Quantum Optics, Royal Institute of Technology, Roslagstullsbacken 21, SE-10691 Stockholm, Sweden.
    Reflection of matter waves in potential structures2002In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 66, no 5, p. 053605-Article in journal (Refereed)
    Abstract [en]

    In this paper the behavior of matter waves in suddenly terminated potential structures is investigated numerically. It is shown that there is no difference between a fully quantum mechanical treatment and a semiclassical one with regards to energy redistribution. For the quantum case it is demonstrated that there can be substantial reflection at the termination. The neglect of backscattering by the semiclassical method brings about major differences in the case of low kinetic energies. A simple phenomenological model is shown to partially explain the observed backscattering using dynamics of reduced dimensionality.

  • 15.
    Jääskeläinen, Markku
    et al.
    Optical Sciences Center, The University of Arizona, Tucson, Arizona 85721, USA.
    Zhang, Weiping
    Department of Physics, Tsinghua University, Beijing 100084, China.
    Meystre, Pierre
    Optical Sciences Center, The University of Arizona, Tucson, Arizona 85721, USA.
    Limits to phase resolution in matter-wave interferometry2004In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 70, no 6, article id 063612Article in journal (Refereed)
    Abstract [en]

    We study the quantum dynamics of a two-mode Bose-Einstein condensate in a time-dependent symmetric double-well potential using analytical and numerical methods. The effects of internal degrees of freedom on the visibility of interference fringes during a stage of ballistic expansion are investigated varying particle number, nonlinear interaction sign and strength, as well as tunneling coupling. Expressions for the phase resolution are derived and the possible enhancement due to squeezing is discussed. In particular, the role of the superfluid-Mott insulator crossover and its analog for attractive interactions is recognized.

  • 16.
    Jääskeläinen, Markku
    et al.
    Institute of Fundamental Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, Massey University, Manawatu Campus, Private Bag 11 222, Palmerston North 4442, New Zealand.
    Zulicke, Ulrich
    Massey University.
    Anomalous spin-related quantum phase in mesoscopic hole rings2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 15, article id 155326Article in journal (Refereed)
    Abstract [en]

    We have obtained numerically exact results for the spin-related geometric quantum phases that arise in p-type semiconductor ring structures. The interplay between gate-controllable (Rashba) spin splitting and quantum-confinement-induced mixing between hole-spin states causes a much higher sensitivity of magnetoconductance oscillations to external parameters than previously expected. Our results imply a much-enhanced functionality of hole-ring spin-interference devices and shed new light on recent experimental findings.

  • 17.
    Weatherall, James Owen
    et al.
    Stevens Institute of Technology.
    Search, Christopher P.
    Stevens Institute of Technology.
    Jääskeläinen, Markku
    Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030, USA.
    Quantum control of electromagnetically induced transparency dispersion via atomic tunneling in a double-well Bose-Einstein condensate2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 78, no 1, article id 013830Article in journal (Refereed)
    Abstract [en]

    Electromagnetically induced transparency (EIT) is an important tool for controlling light propagation and nonlinear wave mixing in atomic gases with potential applications ranging from quantum computing to table top tests of general relativity. Here we consider EIT in an atomic Bose-Einstein condensate (BEC) trapped in a double-well potential. A weak probe laser propagates through one of the wells and interacts with atoms in a three-level Lambda configuration. The well through which the probe propagates is dressed by a strong control laser with Rabi frequency Omega(mu), as in standard EIT systems. Tunneling between the wells at the frequency g provides a coherent coupling between identical electronic states in the two wells, which leads to the formation of interwell dressed states. The macroscopic interwell coherence of the BEC wave function results in the formation of two ultranarrow absorption resonances for the probe field that are inside of the ordinary EIT transparency window. We show that these new resonances can be interpreted in terms of the interwell dressed states and the formation of a type of dark state involving the control laser and the interwell tunneling. To either side of these ultranarrow resonances there is normal dispersion with very large slope controlled by g. We discuss prospects for observing these ultranarrow resonances and the corresponding regions of high dispersion experimentally.

  • 18.
    Zivkovic, Marko
    et al.
    Stevens Institute of Technology.
    Jääskeläinen, Markku
    Dalarna University, School of Technology and Business Studies, Physics. Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
    Search, Christopher P.
    Stevens Institute of Technology.
    Djuric, Ivana
    Stevens Institute of Technology.
    Sagnac rotational phase shifts in a mesoscopic electron interferometer with spin-orbit interactions2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 11, article id 115306Article in journal (Refereed)
    Abstract [en]

    The Sagnac effect is an important phase coherent effect in optical and atom interferometers where rotations of the interferometer with respect to an inertial reference frame result in a shift in the interference pattern proportional to the rotation rate. Here, we analyze the Sagnac effect in a mesoscopic semiconductor electron interferometer. We include in our analysis the Rashba spin-orbit interactions in the ring. Our results indicate that spin-orbit interactions increase the rotation-induced phase shift. We discuss the potential experimental observability of the Sagnac phase shift in such mesoscopic systems.

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