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  • 1. Andersson, E.
    et al.
    Calarco, T.
    Folman, R.
    Andersson, L. Mauritz
    Hessmo, B.
    Schmiedmayer, J.
    Multimode interferometer for guided matter waves2002In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 88, no 10Article in journal (Refereed)
    Abstract [en]

    Atoms can be trapped and guided with electromagnetic fields, using nanofabricated structures. We describe the fundamental features of an interferometer for guided matter waves, built of two combined Y-shaped beam splitters. We find that such a device is expected to exhibit high contrast fringes even in a multimode regime, analogous to a white light interferometer.

  • 2. Andersson, L. Mauritz
    Quantum dynamics using a discretized coherent state representation: An adaptive phase space method2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, no 3, p. 1158-1165Article in journal (Refereed)
    Abstract [en]

    We introduce a discretized coherent state representation (DCSR) for quantum dynamics. Expansion of a wave function in the nonorthogonal slightly overcomplete set is made with an identity operator computed using an iterative refinement method. Calculating the inverse of the overlap matrix is not necessary. The result is an accurate and efficient representation, where you only put basis functions in the region of phase space where the wave function is nonvanishing. Compared to traditional spatial grid methods, fewer grid points are needed. The DCSR can be viewed as an application of the Weyl-Heisenberg frame and extends it into a useful computational method. A scheme for fully quantum mechanical propagation is constructed and applied to the realistic problem of highly excited vibration in the heavy diatomic molecule Rb-2. Compared to split-operator propagation in a conventional spatial grid, an order of magnitude longer time steps can be taken and fewer grid points are needed. The computational effort scales linearly with the number of basis functions. Nonreflecting boundary conditions are a natural property of the representation and is illustrated in a model of predissociation.

  • 3. Andersson, L. Mauritz
    et al.
    Aberg, J.
    Karlsson, H. O.
    Goscinski, O.
    Properties of a discretized coherent state representation and the relation to Gabor analysis2002In: Journal of Physics A: Mathematical and General, ISSN 0305-4470, E-ISSN 1361-6447, Vol. 35, no 36, p. 7787-7801Article in journal (Refereed)
    Abstract [en]

    Properties of a discretized coherent state representation (DCSR) and its connection to Gabor frame analysis are discussed. The DCSR approach was recently shown (Andersson L M 2001 J. Chem. Phys. 115 1158) to yield a practical computational scheme for quantum dynamics, and an iterative scheme for finding the identity operator was proposed. In the present work, we suggest a proof of fast convergence of the iterative scheme for computing the canonical dual to any given countable frame in a Hilbert space. The method of frames is concerned with the use of a non-orthogonal, over-complete set of functions for expansion of an arbitrary function. We also introduce the concept of 'representations of the identity operator' and show how to expand arbitrary vectors using the frame elements, without explicit diagonalization to an orthonormal basis. Numerical examples that illustrate the method are shown.

  • 4. Andersson, L. Mauritz
    et al.
    Burmeister, F.
    Karlsson, H. O.
    Goscinski, O.
    Nonadiabatic effects in the photoelectron spectra of HCl and DCl. II. Theory2002In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 65, no 1Article in journal (Refereed)
    Abstract [en]

    The vibrationally resolved photoelectron spectra of HCl and DCl in the 25-28 eV region were computed using a time-dependent approach for the nuclear dynamics. The spectral features cannot be understood without including a nonadiabatic coupling between the dissociative 3 (2)Sigma(+) state and the bound 4 (2)Sigma(+) state in the adiabatic picture. Alternatively, in the diabatic picture a dissociative two-hole-one-particle state interacts with a bound one-hole state. The molecular system is of intermediate coupling strength, i.e., it cannot be described by a single potential-energy curve. The interaction between a bound and a dissociative state leads to Fano resonances superimposed on a broad back-round, as observed in the experimental spectra [Burmeister et al., Phys. Rev. A 65, 012704 (2001)]. From modified potential-energy curves, all features of the experimental spectra, including Fano resonance parameters and lifetimes, were reproduced. From the simulations we observe that two additional peaks in the experimental DCl spectra should appear if the resolution were to be enhanced to around 10 meV.

  • 5.
    Andersson, Mauritz
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Berglind, Eilert
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Björk, Gunnar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Orbital angular momentum modes do not increase the channel capacity in communication links2015In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, article id 043040Article in journal (Refereed)
    Abstract [en]

    The orbital momentum of optical or radio waves can be used as a degree of freedom to transmit information. However, mainly for technical reasons, this degree of freedom has not been widely used in communication channels. The question is if this degree of freedom opens up a new, hitherto unused 'communication window' supporting 'an infinite number of channels in a given, fixed bandwidth' in free space communication as has been claimed? We answer this question in the negative by showing that on the fundamental level, the mode density, and thus room for mode multiplexing, is the same for this degree of freedom as for sets of modes lacking angular momentum. In addition we show that modes with angular momentum are unsuitable for broadcasting applications due to excessive crosstalk or a poor signal-to-noise ratio.

  • 6. Burmeister, F.
    et al.
    Andersson, L. Mauritz
    Ohrwall, G.
    Richter, T.
    Zimmermann, P.
    Godehusen, K.
    Martins, M.
    Karlsson, H. O.
    Sorensen, S. L.
    Bjorneholm, O.
    Feifel, R.
    Wiesner, K.
    Goscinski, O.
    Karlsson, L.
    Svensson, S.
    Yencha, A. J.
    A study of the inner-valence ionization region in HCl and DCl2004In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 37, no 6, p. 1173-1183Article in journal (Refereed)
    Abstract [en]

    An in-depth photoionization study of the inner-valence electrons in HCl and DCl has been performed using synchrotron radiation. A series of photoelectron spectra of HCl were obtained at a resolution of 23 meV over the binding energy range 25-30.5 eV at various excitation energies and at two different electron collection angles relative to the plane of polarization of the undulator radiation. In addition, photoelectron spectra of DCl were recorded at two different excitation energies. These spectra were compared directly with the threshold photoelectron spectra of HCl and DCl that were recorded previously under similar resolution conditions (similar to30 meV). This comparative study reveals new information on the nature of the numerous band systems observed in this binding energy region. In addition, we present the experimental confirmation of the theoretical prediction given by Andersson et al (2001 Phys. Rev. A 65 012705) that a vibrational progression showing interference structure would appear in the main inner-valence ionization band in the photoelectron spectrum of DCl at a resolution of 10 meV.

  • 7. Feenstra, L.
    et al.
    Andersson, L. Mauritz
    Schmiedmayer, J.
    Microtraps and Atom Chips: Toolboxes for cold atom physics2004In: General Relativity and Gravitation, ISSN 0001-7701, E-ISSN 1572-9532, Vol. 36, no 10, p. 2317-2329Article in journal (Refereed)
    Abstract [en]

    Magnetic microtraps and Atom Chips are safe, small-scale, reliable and flexible tools to prepare ultra-cold and degenerate atom clouds as sources for various atom-optical experiments. We present an overview of the possibilities of the devices and indicate how a microtrap can be used to prepare and launch a Bose-Einstein condensate for use in an atom clock or an interferometer.

  • 8. Johansson, Markus
    et al.
    Sjöqvist, Erik
    Andersson, L. Mauritz
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Ericsson, Marie
    Hessmo, Bjoern
    Singh, Kuldip
    Tong, D. M.
    Robustness of nonadiabatic holonomic gates2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 86, no 6, p. 062322-Article in journal (Refereed)
    Abstract [en]

    The robustness to different sources of error of the scheme for nonadiabatic holonomic gates proposed previously [New J. Phys. 14, 103035 (2012)] is investigated. Open system effects as well as errors in the driving fields are considered. It is found that the gates can be made error resilient by using sufficiently short pulses. The principal limit of how short the pulses can be made is given by the breakdown of the quasi-monochromatic approximation. A comparison with the resilience of adiabatic gates is carried out.

  • 9. Krueger, P.
    et al.
    Andersson, L. Mauritz
    Wildermuth, S.
    Hofferberth, S.
    Haller, E.
    Aigner, S.
    Groth, S.
    Bar-Joseph, I.
    Schmiedmayer, J.
    Potential roughness near lithographically fabricated atom chips2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 6Article in journal (Refereed)
    Abstract [en]

    Potential roughness has been reported to severely impair experiments in magnetic microtraps. We show that these obstacles can be overcome as we measure disorder potentials that are reduced by two orders of magnitude near lithographically patterned high-quality gold layers on semiconductor atom chip substrates. The spectrum of the remaining field variations exhibits a favorable scaling. A detailed analysis of the magnetic field roughness of a 100-mu m-wide wire shows that these potentials stem from minute variations of the current flow caused by local properties of the wire rather than merely from rough edges. A technique for further reduction of potential roughness by several orders of magnitude based on time-orbiting magnetic fields is outlined.

  • 10.
    Kruger, P.
    et al.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Hofferberth, S.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Haller, E.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Wildermuth, S.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Andersson, L. M.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Garcia, D. Gallego
    Physikalisches Institut, Universität Heidelberg, Germany .
    Aigner, S.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Groth, S.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Bar-Joseph, I.
    Department of Condensed Matter Physics, Weizmann Institute of Science, Israel .
    Schmiedmayer, J.
    Physikalisches Institut, Universität Heidelberg, Germany .
    Ultracold atoms on atom chips : Manipulation at the mu m distance scale2005In: ATOMIC PHYSICS 19 : AIP Conference Proceedings: Volume: 770   , 2005, Vol. 770, p. 144-153Conference paper (Refereed)
    Abstract [en]

    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom‐surface distances can be reduced to microns. We discuss experiments in this regime and potential obstacles and solutions. We show that appropriate fabrication techniques lead to a reduction of disorder potentials so that one‐dimensional condensates can be prepared. We demonstrate how electrostatic potentials can be used to modify magnetic trapping potentials and how they can be used to study condensate formation in situations of different dimensionality. © 2005 American Institute of Physics

  • 11. Kruger, P.
    et al.
    Wildermuth, S.
    Hofferberth, S.
    Haller, E.
    Andersson, L. M.
    Garcia, D. G.
    Groth, S.
    Haase, A.
    Wilzbach, M.
    Schmiedmayer, J.
    Bar-Joseph, I.
    Integrated matter wave optics on atom chips2005In: EQEC ’05. European Quantum Electronics Conference, 2005., 2005, p. 270-270Conference paper (Refereed)
  • 12.
    Kruger, Peter
    et al.
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Hofferberth, Sebastian
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Schumm, Thorsten
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Lesanovsky, Igor
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Andersson, L Mauritz
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Wildermuth, Stephan
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Groth, Sönke
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Bar-Joseph, Israel
    Weizmann Institute of Science, Rehovot, 76100 Israel.
    Schmiedmayer, Jörg
    Phys. Inst., Univ. Heidelberg, Heidelberg .
    Coherent matter wave optics on an atom chip2006In: Lasers and Electro-Optics, 2006 and 2006 Quantum Electronics and Laser Science Conference CLEO/QELS 2006 Conference on, 2006, p. 1-2Conference paper (Refereed)
    Abstract [en]

    Coherent manipulation of matter waves in microscopic trapping potentials facilitates both fundamental and technological applications. Here we focus on experiments with a microscopic integrated interferometer that demonstrate coherent operation on an atom chip.

  • 13.
    Krüger, Peter
    et al.
    Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany.
    Haase, Albrecht
    Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany.
    Andersson, Mauritz
    Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany.
    Schmiedmayer, Jörg
    Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany.
    Quantum Information Processing with Neutral Atoms on Atom Chips2005In: Quantum Information Processing / [ed] Prof. Dr.-Ing. Thomas Beth, Prof. Dr Gerd Leuchs, Wiley-VCH Verlagsgesellschaft, 2005, 2, p. 298-311Chapter in book (Other academic)
    Abstract [en]

    This chapter contains sections titled: * Introduction * The Atom Chip * Combined Magneto-Electric Traps * RF-induced Adiabatic Potentials for Manipulating Atoms * Imperfections in the Atom Chip: Disorder Potentials * The Qubit * Entangling Qubits * Quantum Gate via Cold Controlled Collisions * Motional Qubit Gates with Controlled Collisions * Input/Output * Qubit Detection * Quantum Input/Output * Noise and Decoherence * Summary and Conclusion * References

  • 14.
    Krüger, Peter
    et al.
    Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany .
    Wildermuth, Stephan
    Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany .
    Hofferberth, Sebastian
    Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany .
    Andersson, L Mauritz
    Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany .
    Groth, Sönke
    Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany .
    Bar-Joseph, Israel
    Institute for Condensed Matter Physics, The Weizmann Institute of Science, Rehovot 76100, Israel .
    Schmiedmayer, Jörg
    Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany .
    Cold atoms close to surfaces: measuring magnetic field roughness and disorder potentials2005In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 19, no 1, p. 56-65Article in journal (Refereed)
    Abstract [en]

    Microscopic atom optical devices integrated on atom chips allow to precisely control and manipulate ultra-cold ( T < 1 µK) neutral atoms and Bose-Einstein condensates (BECs) close to surfaces. The relevant energy scale of a BEC is extremely small (down to < 10 −11 eV). Consequently, BECs can be utilized as a sensor for variations of the potential energy of the atoms close to the surface. Here we describe how to use trapped atoms as a measurement device and analyze the performance and flexibility of the field sensor. We demonstrate microscopic magnetic imaging with simultaneous high spatial resolution (3 µm) and high field sensitivity (4 nT). With one dimensional BECs, we probe the magnetic field variations close to the surface at distances down to a few microns. Measurements of the magnetic field of a 100 µm wide current carrying wire imply that the magnetic field variations stem from residual variations of the current flow direction, resulting from local properties of the wire. These disorder potentials found near lithographically fabricated wires are two orders of magnitude smaller than those measured close to electroplated conductors.

  • 15. Lesanovsky, I.
    et al.
    Schumm, T.
    Hofferberth, S.
    Andersson, L. Mauritz
    Kruger, P.
    Schmiedmayer, J.
    Adiabatic radio-frequency potentials for the coherent manipulation of matter waves2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 73, no 3Article in journal (Refereed)
    Abstract [en]

    Adiabatic dressed state potentials are created when magnetic substates of trapped atoms are coupled by a radio-frequency field. We discuss their theoretical foundations and point out fundamental advantages over potentials purely based on static fields. The enhanced flexibility enables one to implement numerous configurations, including double wells, Mach-Zehnder, and Sagnac interferometers which even allows for internal state-dependent atom manipulation. These can be realized using simple and highly integrated wire geometries on atom chips.

  • 16.
    Neff, Curtis W.
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Coupled resonator optical waveguide structures with highly dispersive media2006In: Optoeletronic Materials and Devices, Pts 1 and 2 / [ed] Lee, YH; Koyama, F; Luo, Y, BELLINGHAM, WA: SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6352, p. U316-U324Conference paper (Refereed)
    Abstract [en]

    Enhanced slow light propagation is predicted in a coupled resonator optical waveguide structure possessing highly dispersive elements using the finite-difference time-domain method. The group velocity is shown to be below 0.01c(0).

  • 17. Neff, Curtis W.
    et al.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Coupled resonator optical waveguide structures with highly dispersive media2007In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 15, no 16, p. 10362-10369Article in journal (Refereed)
    Abstract [en]

    Analysis of photonic crystal coupled resonator optical waveguide (CROW) structures with a highly dispersive background medium is presented. A finite-difference time-domain algorithm was employed which contains an exact representation of the permittivity of a three-level atomic system which exhibits electromagnetically induced transparency (EIT). We find that the coupling strength between nearest-neighbor cavities in the CROW decreases with increasing steepness of the background dispersion, which is continuously tunable as it is directly related to the control field Rabi frequency. The weaker coupling decreases the speed of pulse propagation through the waveguide. In addition, due to the dispersive nature of the EIT background, the CROW band shape is tuned around a fixed k-point. Thus, the EIT background enables dynamic tunability of the CROW band shape and the group velocity in the structure at a fixed operating point in momentum space.

  • 18. Neff, Curtis W.
    et al.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Modelling electromagnetically induced transparency media using the finite-difference time-domain method2007In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 9Article in journal (Refereed)
    Abstract [en]

    Time-domain electromagnetic modelling of complex structures which include both non-dispersive media and media exhibiting electromagnetically induced transparency (EIT) require a general, robust calculation method such as finite-difference time-domain (FDTD). We propose a complex-valued, exact two-pole representation of the permittivity of a three-level system which is suitable for integration into the FDTD algorithm via the auxiliary differential equation method. Our calculation model confirmed reported results which were calculated with an approximate representation of the EIT permittivity. Additionally, propagation calculations which mimic slow light experiments were performed. A major advantage of our representation is the ease with which changes in the control field Rabi frequency can be implemented by using a time-dependent permittivity.

  • 19.
    Neff, Curtis W.
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qui, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Enhanced Transmission in Dynamically Tuned Optical Microresonator Possessing Highly Dispersive Media2007In: ECIO European Conference on Integrated Optics 2007, 2007, p. WH4-Conference paper (Other academic)
    Abstract [en]

    We present a theoretical study of an opticalmicroresonator system which contains a electromagneticallyinduced transparency medium within the resonator.We find that a time-dependent tuning of thedispersive properties of the resonator medium resultsin an enhanced transmission spectrum.

  • 20.
    Qiu, Min
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Neff, Curtis
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Coupled resonator optical waveguides with electromagnetically induced transparent media2006In: Technical digest: July 23 - 26, 2006, OSA Headquarters, Washington, DC, USA, Optical Society of America, 2006Conference paper (Refereed)
    Abstract [en]

    We numerically demonstrate ultra slow light in a coupled optical resonator waveguide embedded in a highly dispersive medium. This combination dramatically reduces the propagation speed of light pulses in the structure to below 1% c0.

  • 21. Schumm, T.
    et al.
    Hofferberth, S.
    Andersson, L. Mauritz
    Wildermuth, S.
    Groth, S.
    Bar-Joseph, I.
    Schmiedmayer, J.
    Kruger, P.
    Matter-wave interferometry in a double well on an atom chip2005In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 1, no 1, p. 57-62Article in journal (Refereed)
    Abstract [en]

    Matter-wave interference experiments enable us to study matter at its most basic, quantum level and form the basis of high-precision sensors for applications such as inertial and gravitational field sensing. Success in both of these pursuits requires the development of atom-optical elements that can manipulate matter waves at the same time as preserving their coherence and phase. Here, we present an integrated interferometer based on a simple, coherent matter-wave beam splitter constructed on an atom chip. Through the use of radio-frequency-induced adiabatic double-well potentials, we demonstrate the splitting of Bose-Einstein condensates into two clouds separated by distances ranging from 3 to 80 mu m, enabling access to both tunnelling and isolated regimes. Moreover, by analysing the interference patterns formed by combining two clouds of ultracold atoms originating from a single condensate, we measure the deterministic phase evolution throughout the splitting process. We show that we can control the relative phase between the two fully separated samples and that our beam splitter is phase-preserving.

  • 22. Schumm, T.
    et al.
    Krueger, P.
    Hofferberth, S.
    Lesanovsky, I.
    Wildermuth, S.
    Groth, S.
    Bar-Joseph, I.
    Andersson, L. Mauritz
    Schmiedmayer, J.
    A double well interferometer on an atom chip2006In: Quantum Information Processing, ISSN 1570-0755, E-ISSN 1573-1332, Vol. 5, no 6, p. 537-558Article in journal (Refereed)
    Abstract [en]

    Radio-Frequency coupling between magnetically trapped atomic states allows to create versatile adiabatic dressed state potentials for neutral atom manipulation. Most notably, a single magnetic trap can be split into a double well by controlling amplitude and frequency of an oscillating magnetic field. We use this to build an integrated matter wave interferometer on an atom chip. Transverse splitting of quasi one-dimensional Bose-Einstein condensates over a wide range from 3 to 80 mu m is demonstrated, accessing the tunnelling regime as well as completely isolated sites. By recombining the two split BECs in time of flight expansion, we realize a matter wave interferometer. The observed interference pattern exhibits a stable relative phase of the two condensates, clearly indicating a coherent splitting process. Furthermore, we measure and control the deterministic phase evolution throughout the splitting process. RF induced potentials are especially suited for integrated micro manipulation of neutral atoms on atom chips: designing appropriate wire patterns enables control over the created potentials to the (nanometer) precision of the fabrication process. Additionally, hight local RF amplitudes can be obtained with only moderate currents. This new technique can be directly implemented in many existing atom chip experiments.

  • 23. Sjöqvist, Erik
    et al.
    Tong, D. M.
    Andersson, L. Mauritz
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hessmo, Björn
    Johansson, Markus
    Singh, Kuldip
    Non-adiabatic holonomic quantum computation2012In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, p. 103035-Article in journal (Refereed)
    Abstract [en]

    We develop a non-adiabatic generalization of holonomic quantum computation in which high-speed universal quantum gates can be realized using non-Abelian geometric phases. We show how a set of non-adiabatic holonomic one-and two-qubit gates can be implemented by utilizing optical transitions in a generic three-level 3 configuration. Our scheme opens up the possibility of realizing universal holonomic quantum computation on qubits characterized by short coherence time.

  • 24. Smith, David A.
    et al.
    Aigner, Simon
    Hofferberth, Sebastian
    Gring, Michael
    Andersson, Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Wildermuth, Stefan
    Krueger, Peter
    Schneider, Stephan
    Schumm, Thorsten
    Schmiedmayer, Joerg
    Absorption imaging of ultracold atoms on atom chips2011In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 9, p. 8471-8485Article in journal (Refereed)
    Abstract [en]

    Imaging ultracold atomic gases close to surfaces is an important tool for the detailed analysis of experiments carried out using atom chips. We describe the critical factors that need be considered, especially when the imaging beam is purposely reflected from the surface. In particular we present methods to measure the atom-surface distance, which is a prerequisite for magnetic field imaging and studies of atom surface-interactions.

  • 25.
    Tidström, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Andersson, Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Manipulating light pulses during storage and readoutManuscript (preprint) (Other academic)
  • 26.
    Tidström, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Andersson, Mauritz
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Overtone generation in driven coherent media2009In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 79, no 6, p. 063832-1-063832-7Article in journal (Refereed)
    Abstract [en]

    We observe overtone signal generation of a near-resonant bichromatic light field interacting with 85Rb on the Zeeman split F=2F=1,2,3 hyperfine transitions of the D2 line at 780 nm. A nonperturbative theoretical model for electromagnetically induced transparency is developed in order to explain this phenomenon. Assuming a  system, an explicit and convenient expression for the atomic coherence is derived from the Lindblad equation assuming a phase-damping channel. The light field state is parametrically varied through one beat note of the bichromatic field and the spatial properties are studied by numerically solving the coupled-wave equation. The polarization characteristics is analyzed on the Poincaré sphere, which together with field intensity analysis offers a simple explanation of the harmonic beating signal due to Stokes vector rotation around the Poincaré sphere and decoherence effects. The experimental data and theoretical analysis focus on the first and second harmonics, although many higher harmonics are present. A distinct and narrow minimum of the second-harmonic generation is measured on two-photon resonance.

  • 27.
    Tidström, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ericsson, Marie
    Sjöqvist, Erik
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Open-system effects on slow light and electromagnetically induced transparency2011In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, no 13, p. 135501-Article in journal (Refereed)
    Abstract [en]

    The coherence properties of a three-level Lambda-system influenced by a Markovian environment are analysed. A coherence vector formalism is used and a vector form of the Lindblad equation is derived. Together with decay channels from the upper state, open-system channels acting on the subspace of the two lower states are investigated, i.e. depolarization, dephasing and amplitude damping channels. We derive an analytic expression for the coherence vector and the concomitant optical susceptibility, and analyse how the different channels influence the optical response. This response depends non-trivially on the type of open-system interaction present, and even gain can be obtained. We also present a geometrical visualization of the coherence vector as an aid to understand the system response.

  • 28.
    Tidström, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Delay bandwidth product of electromagnetically induced transparency media2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 5, p. 053803-Article in journal (Refereed)
    Abstract [en]

    The limitations on the delay-bandwidth product (DBP) in an electromagnetically induced transparency medium are investigated analytically by studying the susceptibility of the system, derived through Lindblad's master equation, including dephasing. The effect of inhomogeneous broadening is treated. It is shown that the DBP for a given material is fundamentally limited by the frequency-dependent absorption, while the residual absorption limits the penetration length of a pulse. Simple expression for the optimal choice of parameters to maximize the DBP are derived. Also, the length of a device is presented as a function of DBP and control-field Rabi frequency. Supporting these results, numerical calculations are carried out through the Maxwell-Bloch equations in the slowly varying envelope approximation. The results are scalable, hence they apply to the case of atoms or molecules in a gas as well as quantum dots and wells.

  • 29.
    Tidström, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Andersson, L Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Pulse distortion in EIT medium2006In: Slow and Fast Light 2006, 2006, p. WB6-Conference paper (Other academic)
    Abstract [en]

    We analyze pulse-distortion due to propagation through medium exhibiting Electromagnetically Induced Transparency. Separately investigating real and imaginary parts of the susceptibility; the latter being the limiting factor, by analytical and numerical arguments.

  • 30.
    Tidström, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Neff, Curtis W.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Andersson, L. Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Photonic crystal cavity embedded in electromagnetically induced transparency media2010In: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 12, no 3, p. 035105-Article in journal (Refereed)
    Abstract [en]

    Photonic crystal cavities are known for their high quality factor and small modal volume. Electromagnetically induced transparency (EIT) is known for its dramatic dispersion. We study the fundamental cavity mode of a two-dimensional photonic crystal embedded in an EIT medium. Comparison of finite-difference time-domain simulations with an analytical intracavity-EIT model yields similar results: the modal density of the photonic crystal cavity increases and the cavity resonance is pulled from the empty cavity resonance to the two-photon resonance of the EIT medium. As a consequence, the quality factor may be enhanced by more than two orders of magnitude. For a miniature sized 2.5 lambda x 2.5 lambda photonic crystal cavity based on a 5 x 5 high index rod structure with a missing centre rod, the quality factor can be increased from 200 to 40 000.

  • 31.
    Wildermuth, Stephan
    et al.
    Physikalisches Institut, Universität Heidelberg.
    Hofferberth, Sebastian
    Physikalisches Institut, Universität Heidelberg.
    Lesanovsky, Igor
    Physikalisches Institut, Universität Heidelberg.
    Haller, Elmar
    Physikalisches Institut, Universität Heidelberg.
    Andersson, L. Mauritz
    Physikalisches Institut, Universität Heidelberg.
    Groth, Sönke
    Physikalisches Institut, Universität Heidelberg.
    Bar-Joseph, Israel
    Department of Condensed Matter Physics, The Weizmann Institute of Science.
    Krüger, Peter
    Physikalisches Institut, Universität Heidelberg.
    Schmiedmayer, Jörg
    Physikalisches Institut, Universität Heidelberg.
    Bose-Einstein condensates: Microscopic magnetic-field imaging2005In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 435, no 7041, p. 440-Article in journal (Other academic)
1 - 31 of 31
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