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Link M, Gao K, Kell A, Breyer M, Eberz D, Rauf B, Köhl M. Machine Learning the Phase Diagram of a Strongly Interacting Fermi Gas. Phys Rev Lett 2023; 130:203401. [PMID: 37267577 DOI: 10.1103/physrevlett.130.203401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 03/31/2023] [Indexed: 06/04/2023]
Abstract
We determine the phase diagram of strongly correlated fermions in the crossover from Bose-Einstein condensates of molecules (BEC) to Cooper pairs of fermions (BCS) utilizing an artificial neural network. By applying advanced image recognition techniques to the momentum distribution of the fermions, a quantity which has been widely considered as featureless for providing information about the condensed state, we measure the critical temperature and show that it exhibits a maximum on the bosonic side of the crossover. Additionally, we backanalyze the trained neural network and demonstrate that it interprets physically relevant quantities.
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Affiliation(s)
- M Link
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - K Gao
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - A Kell
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - M Breyer
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - D Eberz
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - B Rauf
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - M Köhl
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
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2
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Kell A, Link M, Breyer M, Hoffmann A, Köhl M, Gao K. A compact and fast magnetic coil for the manipulation of quantum gases with Feshbach resonances. Rev Sci Instrum 2021; 92:093202. [PMID: 34598519 DOI: 10.1063/5.0049518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 08/27/2021] [Indexed: 06/13/2023]
Abstract
Cold atom experiments commonly use broad magnetic Feshbach resonances to manipulate the interaction between atoms. In order to induce quantum dynamics by a change in the interaction strength, rapid (∼μs) magnetic field changes over several tens of Gauss are required. Here, we present a compact design of a coil and its control circuit for a change in the magnetic field up to 36 G in 3 µs. The setup comprises two concentric solenoids with minimal space requirements, which can be readily added to existing apparatuses. This design makes the observation of non-equilibrium physics with broad Feshbach resonances accessible.
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Affiliation(s)
- A Kell
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - M Link
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - M Breyer
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - A Hoffmann
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - M Köhl
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - K Gao
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
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3
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Gall M, Chan CF, Wurz N, Köhl M. Simulating a Mott Insulator Using Attractive Interaction. Phys Rev Lett 2020; 124:010403. [PMID: 31976738 DOI: 10.1103/physrevlett.124.010403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Indexed: 06/10/2023]
Abstract
We study the particle-hole symmetry in the Hubbard model using ultracold fermionic atoms in an optical lattice. We demonstrate the mapping between charge and spin degrees of freedom and, in particular, show the occurrence of a state with "incompressible" magnetization for attractive interactions. Our results present a novel approach to quantum simulation by giving access to strongly correlated phases of matter through an experimental mapping to easier detectable observables.
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Affiliation(s)
- M Gall
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - C F Chan
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - N Wurz
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - M Köhl
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
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4
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Drewes JH, Miller LA, Cocchi E, Chan CF, Wurz N, Gall M, Pertot D, Brennecke F, Köhl M. Antiferromagnetic Correlations in Two-Dimensional Fermionic Mott-Insulating and Metallic Phases. Phys Rev Lett 2017; 118:170401. [PMID: 28498688 DOI: 10.1103/physrevlett.118.170401] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Indexed: 06/07/2023]
Abstract
We experimentally study the emergence of antiferromagnetic correlations between ultracold fermionic atoms in a two-dimensional optical lattice with decreasing temperature. We determine the uniform magnetic susceptibility of the two-dimensional Hubbard model from simultaneous measurements of the in situ density distribution of both spin components. At half filling and strong interactions our data approach the Heisenberg model of localized spins with antiferromagnetic correlations. Moreover, we observe a fast decay of magnetic correlations when doping the system away from half filling.
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Affiliation(s)
- J H Drewes
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - L A Miller
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - E Cocchi
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - C F Chan
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - N Wurz
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - M Gall
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - D Pertot
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - F Brennecke
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - M Köhl
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
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5
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Drewes JH, Cocchi E, Miller LA, Chan CF, Pertot D, Brennecke F, Köhl M. Thermodynamics versus Local Density Fluctuations in the Metal-Mott-Insulator Crossover. Phys Rev Lett 2016; 117:135301. [PMID: 27715101 DOI: 10.1103/physrevlett.117.135301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Indexed: 06/06/2023]
Abstract
The crossover between a metal and a Mott insulator leads to a localization of fermions from delocalized Bloch states to localized states. We experimentally study this crossover using fermionic atoms in an optical lattice by measuring thermodynamic and local (on-site) density correlations. In the metallic phase at incommensurable filling we observe the violation of the local fluctuation-dissipation theorem indicating that the thermodynamics of the system cannot be characterized by local observables alone. In contrast, in the Mott insulator we observe the convergence of local and thermodynamic fluctuations indicating the absence of long-range density-density correlations.
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Affiliation(s)
- J H Drewes
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - E Cocchi
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - L A Miller
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - C F Chan
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - D Pertot
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - F Brennecke
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - M Köhl
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
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6
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Grigoriev D, Lazarev S, Schroth P, Minkevich A, Köhl M, Slobodskyy T, Helfrich M, Schaadt D, Aschenbrenner T, Hommel D, Baumbach T. Asymmetric skew X-ray diffraction at fixed incidence angle: application to semiconductor nano-objects. J Appl Crystallogr 2016. [DOI: 10.1107/s1600576716006385] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
A procedure for obtaining three-dimensionally resolved reciprocal-space maps in a skew X-ray diffraction geometry is described. The geometry allows tuning of the information depth in the range from tens of micrometres for symmetric skew diffraction down to tens of nanometres for strongly asymmetric skew geometries, where the angle of incidence is below the critical angle of total external reflection. The diffraction data are processed using a rotation matrix formalism. The whole three-dimensional reciprocal-space map can be measured by performing a single azimuthal rotation of the sample and using a two-dimensional detector, while keeping the angle of incidence and the X-ray information depth fixed (FIXD method). Having a high surface sensitivity under grazing-incidence conditions, the FIXD method can be applied to a large variety of Bragg reflections, particularly polar ones, which provide information on strain and chemical composition separately. In contrast with conventional grazing-incidence diffraction, the FIXD approach reveals, in addition to the lateral (in-plane) components, the vertical (out-of-plane) component of the strain field, and therefore allows the separation of the scattering contributions of strained epitaxial nanostructures by their vertical misfit. The potential of FIXD is demonstrated by resolving the diffraction signal from a single layer of InGaN quantum dots grown on a GaN buffer layer. The FIXD approach is suited to the study of free-standing and covered near-surface nano-objects, as well as vertically extended multilayer structures.
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7
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Meyer HM, Stockill R, Steiner M, Le Gall C, Matthiesen C, Clarke E, Ludwig A, Reichel J, Atatüre M, Köhl M. Direct photonic coupling of a semiconductor quantum dot and a trapped ion. Phys Rev Lett 2015; 114:123001. [PMID: 25860737 DOI: 10.1103/physrevlett.114.123001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Indexed: 06/04/2023]
Abstract
Coupling individual quantum systems lies at the heart of building scalable quantum networks. Here, we report the first direct photonic coupling between a semiconductor quantum dot and a trapped ion and we demonstrate that single photons generated by a quantum dot controllably change the internal state of a Yb^{+} ion. We ameliorate the effect of the 60-fold mismatch of the radiative linewidths with coherent photon generation and a high-finesse fiber-based optical cavity enhancing the coupling between the single photon and the ion. The transfer of information presented here via the classical correlations between the σ_{z} projection of the quantum-dot spin and the internal state of the ion provides a promising step towards quantum-state transfer in a hybrid photonic network.
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Affiliation(s)
- H M Meyer
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - R Stockill
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - M Steiner
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - C Le Gall
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - C Matthiesen
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - E Clarke
- EPSRC National Centre for III-V Technologies, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - A Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität, 44780 Bochum, Germany
| | - J Reichel
- Laboratoire Kastler Brossel, École Normale Supérieure, 24 Rue Lhomond, 75005 Paris, France
| | - M Atatüre
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - M Köhl
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
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8
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Steiner M, Meyer HM, Reichel J, Köhl M. Photon emission and absorption of a single ion coupled to an optical-fiber cavity. Phys Rev Lett 2014; 113:263003. [PMID: 25615321 DOI: 10.1103/physrevlett.113.263003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Indexed: 06/04/2023]
Abstract
We present a light-matter interface which consists of a single 174Yb+ ion coupled to an optical fiber cavity. We observe that photons at 935 nm are mainly emitted into the cavity mode and that correlations between the polarization of the photon and the spin state of the ion are preserved despite the intrinsic coupling into a single-mode fiber. Complementary, when a faint coherent light field is injected into the cavity mode, we find enhanced and polarization dependent absorption by the ion.
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Affiliation(s)
- M Steiner
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - H M Meyer
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom and Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
| | - J Reichel
- Laboratoire Kastler Brossel, École Normale Supérieure, Université Pierre et Marie Curie-Paris 6, CNRS, 24 Rue Lhomond, 75005 Paris, France
| | - M Köhl
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom and Physikalisches Institut, University of Bonn, Wegelerstrasse 8, 53115 Bonn, Germany
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9
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Pertot D, Sheikhan A, Cocchi E, Miller LA, Bohn JE, Koschorreck M, Köhl M, Kollath C. Relaxation dynamics of a Fermi gas in an optical superlattice. Phys Rev Lett 2014; 113:170403. [PMID: 25379905 DOI: 10.1103/physrevlett.113.170403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Indexed: 06/04/2023]
Abstract
This Letter comprises an experimental and theoretical investigation of the time evolution of a Fermi gas following fast and slow quenches of a one-dimensional optical double-well superlattice potential. We investigate both the local tunneling in the connected double wells and the global dynamics towards a steady state, i.e., a time-independent state. The local observables in the steady state resemble those of a thermal equilibrium state, whereas the global properties indicate a strong nonequilibrium situation.
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Affiliation(s)
- D Pertot
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany and Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
| | - A Sheikhan
- HISKP, University of Bonn, Nussallee 14-16, 53115 Bonn, Germany
| | - E Cocchi
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany and Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
| | - L A Miller
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany and Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
| | - J E Bohn
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
| | - M Koschorreck
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany and Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
| | - M Köhl
- Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany and Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
| | - C Kollath
- HISKP, University of Bonn, Nussallee 14-16, 53115 Bonn, Germany
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Minkevich AA, Köhl M, Escoubas S, Thomas O, Baumbach T. Retrieval of the atomic displacements in the crystal from the coherent X-ray diffraction pattern. J Synchrotron Radiat 2014; 21:774-783. [PMID: 24971974 DOI: 10.1107/s1600577514010108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 05/05/2014] [Indexed: 06/03/2023]
Abstract
The retrieval of spatially resolved atomic displacements is investigated via the phases of the direct(real)-space image reconstructed from the strained crystal's coherent X-ray diffraction pattern. It is demonstrated that limiting the spatial variation of the first- and second-order spatial displacement derivatives improves convergence of the iterative phase-retrieval algorithm for displacements reconstructions to the true solution. This approach is exploited to retrieve the displacement in a periodic array of silicon lines isolated by silicon dioxide filled trenches.
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Affiliation(s)
- A A Minkevich
- ANKA/Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - M Köhl
- ANKA/Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - S Escoubas
- Aix-Marseille Université, CNRS, IM2NP, UMR 7334, 13397 Marseille Cedex 20, France
| | - O Thomas
- Aix-Marseille Université, CNRS, IM2NP, UMR 7334, 13397 Marseille Cedex 20, France
| | - T Baumbach
- ANKA/Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
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11
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Kaltenbach T, E.Klimm, Meier T, Köhl M, Weiß K. Testing of Components for Solar Thermal Collectors in Respect of Saline Atmospheres. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.egypro.2014.02.085] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Ratschbacher L, Sias C, Carcagni L, Silver JM, Zipkes C, Köhl M. Decoherence of a single-ion qubit immersed in a spin-polarized atomic bath. Phys Rev Lett 2013; 110:160402. [PMID: 23679585 DOI: 10.1103/physrevlett.110.160402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Indexed: 06/02/2023]
Abstract
We report on the immersion of a spin qubit encoded in a single trapped ion into a spin-polarized neutral atom environment, which possesses both continuous (motional) and discrete (spin) degrees of freedom. The environment offers the possibility of a precise microscopic description, which allows us to understand dynamics and decoherence from first principles. We observe the spin dynamics of the qubit and measure the decoherence times (T(1) and T(2)), which are determined by the spin-exchange interaction as well as by an unexpectedly strong spin-nonconserving coupling mechanism.
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Affiliation(s)
- L Ratschbacher
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE, United Kingdom
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13
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Fröhlich B, Feld M, Vogt E, Koschorreck M, Köhl M, Berthod C, Giamarchi T. Two-dimensional Fermi liquid with attractive interactions. Phys Rev Lett 2012; 109:130403. [PMID: 23030071 DOI: 10.1103/physrevlett.109.130403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2012] [Indexed: 06/01/2023]
Abstract
We realize and study an attractively interacting two-dimensional Fermi liquid. Using momentum-resolved photoemission spectroscopy, we measure the self-energy, determine the contact parameter of the short-range interaction potential, and find their dependence on the interaction strength. We successfully compare the measurements to a theoretical analysis, properly taking into account the finite temperature, harmonic trap, and the averaging over several two-dimensional gases with different peak densities.
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Affiliation(s)
- B Fröhlich
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
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14
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Abstract
The phase transition of Bose-Einstein condensation was studied in the critical regime, where fluctuations extend far beyond the length scale of thermal de Broglie waves. We used matter-wave interference to measure the correlation length of these critical fluctuations as a function of temperature. Observations of the diverging behavior of the correlation length above the critical temperature enabled us to determine the critical exponent of the correlation length for a trapped, weakly interacting Bose gas to be nu = 0.67 +/- 0.13. This measurement has direct implications for the understanding of second-order phase transitions.
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Affiliation(s)
- T Donner
- Institute of Quantum Electronics, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
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15
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Köhl M, Davis MJ, Gardiner CW, Hänsch TW, Esslinger T. Growth of Bose-Einstein condensates from thermal vapor. Phys Rev Lett 2002; 88:080402. [PMID: 11863948 DOI: 10.1103/physrevlett.88.080402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2001] [Revised: 12/10/2001] [Indexed: 05/23/2023]
Abstract
We report on a quantitative study of the growth process of (87)Rb Bose-Einstein condensates. By continuous evaporative cooling we directly control the thermal cloud from which the condensate grows. We compare the experimental data with the results of a theoretical model based on quantum kinetic theory. We find quantitative agreement with theory for the situation of strong cooling, whereas in the weak cooling regime a distinctly different behavior is found in the experiment.
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Affiliation(s)
- M Köhl
- Sektion Physik, Ludwig-Maximilians-Universität, Schellingstrasse 4/III, D-80799 Munich, Germany.
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16
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Abstract
We report on the measurement of the temporal coherence of an atom laser beam extracted from a (87)Rb Bose-Einstein condensate. Reflecting the beam from a potential barrier creates a standing matter wave structure. From the contrast of this interference pattern, observed by magnetic resonance imaging, we have deduced an energy width of the atom laser beam which is Fourier limited by the duration of output coupling. This gives an upper limit for temporal phase fluctuations in the Bose-Einstein condensate.
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Affiliation(s)
- M Köhl
- Sektion Physik, Ludwig-Maximilians-Universität, Schellingstrasse 4/III, D-80799 Munich, Germany
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17
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Abstract
We report on the atom optical manipulation of an atom laser beam. Reflection, focusing, and its storage in a resonator are demonstrated. Precise and versatile mechanical control over an atom laser beam propagating in an inhomogeneous magnetic field is achieved by optically inducing spin flips between atomic ground states with different magnetic moment. The magnetic force acting on the atoms can thereby be effectively switched on and off. The surface of the atom optical element is determined by the resonance condition for the spin flip in the inhomogeneous magnetic field. More than 98% of the incident atom laser beam is reflected specularly.
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Affiliation(s)
- I Bloch
- Sektion Physik, Ludwig-Maximilians-Universität, Schellingstrasse 4/III, D-80799 Munich, Germany
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18
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Joerger R, Forcht K, Gombert A, Köhl M, Graf W. Influence of incoherent superposition of light on ellipsometric coefficients. Appl Opt 1997; 36:319-327. [PMID: 18250677 DOI: 10.1364/ao.36.000319] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Reflections from the back surface of a transparent substrate influence the evaluation of optical constants of thin films from ellipsometric measurements. If the thickness of the substrate is large compared with the coherence length of the light, the relative phase between the p and s mode, which commonly is measured by ellipsometry, cannot be defined properly. We show how the reflections from the back surface of the substrate are taken into account in ellipsometric measurements by calculating the intensities of reflections for arbitrary angles of polarization. Applications of the new method, such as transmittance ellipsometry, ellipsometry at the back surface of the substrate, and the determination of the optical constants at the substrate-layer interface, are compared with measurements.
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19
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Köhl M, Innes JL, Kaufmann E. Reliability of differing densities of sample grids used for the monitoring of forest condition in Europe. Environ Monit Assess 1994; 29:201-220. [PMID: 24221344 DOI: 10.1007/bf00547987] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/1993] [Revised: 07/15/1993] [Indexed: 06/02/2023]
Abstract
Concern about the possible deterioration of forest health led to the establishment in the 1980s of inventories of forest condition throughout Europe. International standardisation of the programmes was sought and a number of recommendations were made concerning sampling and assessment procedures. One of the most important rulings was that the assessment should be made on a systematic grid, the minimum density of which was 16×16 km. However, many countries adopted denser sampling grids, with 4×4 km being used in several countries and 1×1 km being used in the Netherlands. With five or more years of monitoring completed, there is a growing belief that a rapid and irreversible decline in forest health is not occurring. Consequently, some countries/regions are seeking to reduce their annual investment in forest health monitoring.The precision of national/regional estimates of forest health can be directly related to the sample size. As the sample size decreases, so also does the precision of the estimates. This is illustrated using data collected in Switzerland in 1992 and using grid densities of 4×4 km, 8×8 km, 12×12 km and 16×16 km. The value of the data is dependent on the sample size and the degree to which it is broken down (by region or species). The loss of precision associated with most subdivisions at the 8×8 km grid level remains acceptable, but a sharp deterioration in the precision occurs at the 12×12 km and 16×16 km grid levels. This has considerable implications for the interpretation of the inventories from those countries using a 16×16 km grid. In Switzerland, a reduction from the current 4×4 km grid to an 8×8 km grid (i.e. 75% reduction in sample size) would have relatively little impact on the overall results from the annual inventories of forest health.
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Affiliation(s)
- M Köhl
- Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland
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Köhl M, Spreitzer H, Fleischhacker W. Reaktionen von (−)-Ephedrin bzw. (+)-Norpseudoephedrin und Derivaten mit N,N-Dimethylacetamid-dimethylacetal und N,N,-Dimethylformamid-dimethylacetal. Monatsh Chem 1992. [DOI: 10.1007/bf00811546] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Köhl M, Gindele K, Frei U, Häuselmann T. Accelerated ageing test procedures for selective absorber coatings including lifetime estimation and comparison with outdoor test results. ACTA ACUST UNITED AC 1989. [DOI: 10.1016/0165-1633(89)90011-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Brockerhoff P, Höckel M, Holtermüller KH, Köhl M, Weis HJ, Rathgen GH. The influence of oral contraceptives on the composition of bile. Klin Wochenschr 1982; 60:153-7. [PMID: 7078021 DOI: 10.1007/bf01711279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The increased risk of cholelithiasis during intake of oral contraceptives may be due to estrogen-induced saturation of the bile with cholesterol. In a randomized, prospective, crossed-over double-blind study 20 healthy women after roentgenological exclusion of gall-stones received either 1.0 mg of norethindrone acetate and 50 microgram ethinyl estradiol daily - as usual in oral contraception - for 21 days with 7 days of placebo treatment in each cycle or one fifth of this hormone dose in form of a continuous daily medication. After a 4 month's treatment the medication form was crossed-over. At the beginning of the study, before the cross-over and after the study bile was collected by duodenal intubation after a 12-h fast and the lithogenic index as a measure for cholesterol saturation of the bile was determined. No correlation between the dose and the lithogenic index was demonstrated, neither in 15 women, who had used oral contraceptives before the study nor in five women without any previous hormonal contraceptives.
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