Observation of Bose-Einstein Condensation in a Dilute Atomic Vapor
14 Jul 1995-Science (American Association for the Advancement of Science)-Vol. 269, Iss: 5221, pp 198-201
TL;DR: A Bose-Einstein condensate was produced in a vapor of rubidium-87 atoms that was confined by magnetic fields and evaporatively cooled and exhibited a nonthermal, anisotropic velocity distribution expected of the minimum-energy quantum state of the magnetic trap in contrast to the isotropic, thermal velocity distribution observed in the broad uncondensed fraction.
Abstract: A Bose-Einstein condensate was produced in a vapor of rubidium-87 atoms that was confined by magnetic fields and evaporatively cooled. The condensate fraction first appeared near a temperature of 170 nanokelvin and a number density of 2.5 x 10 12 per cubic centimeter and could be preserved for more than 15 seconds. Three primary signatures of Bose-Einstein condensation were seen. (i) On top of a broad thermal velocity distribution, a narrow peak appeared that was centered at zero velocity. (ii) The fraction of the atoms that were in this low-velocity peak increased abruptly as the sample temperature was lowered. (iii) The peak exhibited a nonthermal, anisotropic velocity distribution expected of the minimum-energy quantum state of the magnetic trap in contrast to the isotropic, thermal velocity distribution observed in the broad uncondensed fraction.
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TL;DR: In this article, a review of recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases is presented, focusing on effects beyond standard weakcoupling descriptions, such as the Mott-Hubbard transition in optical lattices, strongly interacting gases in one and two dimensions, or lowest-Landau-level physics in quasi-two-dimensional gases in fast rotation.
Abstract: This paper reviews recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases. It focuses on effects beyond standard weak-coupling descriptions, such as the Mott-Hubbard transition in optical lattices, strongly interacting gases in one and two dimensions, or lowest-Landau-level physics in quasi-two-dimensional gases in fast rotation. Strong correlations in fermionic gases are discussed in optical lattices or near-Feshbach resonances in the BCS-BEC crossover.
6,601 citations
TL;DR: In this article, the authors reviewed the Bose-Einstein condensation of dilute gases in traps from a theoretical perspective and provided a framework to understand the main features of the condensation and role of interactions between particles.
Abstract: The phenomenon of Bose-Einstein condensation of dilute gases in traps is reviewed from a theoretical perspective. Mean-field theory provides a framework to understand the main features of the condensation and the role of interactions between particles. Various properties of these systems are discussed, including the density profiles and the energy of the ground-state configurations, the collective oscillations and the dynamics of the expansion, the condensate fraction and the thermodynamic functions. The thermodynamic limit exhibits a scaling behavior in the relevant length and energy scales. Despite the dilute nature of the gases, interactions profoundly modify the static as well as the dynamic properties of the system; the predictions of mean-field theory are in excellent agreement with available experimental results. Effects of superfluidity including the existence of quantized vortices and the reduction of the moment of inertia are discussed, as well as the consequences of coherence such as the Josephson effect and interference phenomena. The review also assesses the accuracy and limitations of the mean-field approach.
4,782 citations
01 Jan 2011
TL;DR: To understand the central claims of evolutionary psychology the authors require an understanding of some key concepts in evolutionary biology, cognitive psychology, philosophy of science and philosophy of mind.
Abstract: Evolutionary psychology is one of many biologically informed approaches to the study of human behavior. Along with cognitive psychologists, evolutionary psychologists propose that much, if not all, of our behavior can be explained by appeal to internal psychological mechanisms. What distinguishes evolutionary psychologists from many cognitive psychologists is the proposal that the relevant internal mechanisms are adaptations—products of natural selection—that helped our ancestors get around the world, survive and reproduce. To understand the central claims of evolutionary psychology we require an understanding of some key concepts in evolutionary biology, cognitive psychology, philosophy of science and philosophy of mind. Philosophers are interested in evolutionary psychology for a number of reasons. For philosophers of science —mostly philosophers of biology—evolutionary psychology provides a critical target. There is a broad consensus among philosophers of science that evolutionary psychology is a deeply flawed enterprise. For philosophers of mind and cognitive science evolutionary psychology has been a source of empirical hypotheses about cognitive architecture and specific components of that architecture. Philosophers of mind are also critical of evolutionary psychology but their criticisms are not as all-encompassing as those presented by philosophers of biology. Evolutionary psychology is also invoked by philosophers interested in moral psychology both as a source of empirical hypotheses and as a critical target.
4,670 citations
Proceedings Article•
14 Jul 1996TL;DR: The striking signature of Bose condensation was the sudden appearance of a bimodal velocity distribution below the critical temperature of ~2µK.
Abstract: Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.
3,530 citations
TL;DR: In this paper, an experimental demonstration of electromagnetically induced transparency in an ultracold gas of sodium atoms, in which the optical pulses propagate at twenty million times slower than the speed of light in a vacuum, is presented.
Abstract: Techniques that use quantum interference effects are being actively investigated to manipulate the optical properties of quantum systems1. One such example is electromagnetically induced transparency, a quantum effect that permits the propagation of light pulses through an otherwise opaque medium2,3,4,5. Here we report an experimental demonstration of electromagnetically induced transparency in an ultracold gas of sodium atoms, in which the optical pulses propagate at twenty million times slower than the speed of light in a vacuum. The gas is cooled to nanokelvin temperatures by laser and evaporative cooling6,7,8,9,10. The quantum interference controlling the optical properties of the medium is set up by a ‘coupling’ laser beam propagating at a right angle to the pulsed ‘probe’ beam. At nanokelvin temperatures, the variation of refractive index with probe frequency can be made very steep. In conjunction with the high atomic density, this results in the exceptionally low light speeds observed. By cooling the cloud below the transition temperature for Bose–Einstein condensation11,12,13 (causing a macroscopic population of alkali atoms in the quantum ground state of the confining potential), we observe even lower pulse propagation velocities (17?m?s−1) owing to the increased atom density. We report an inferred nonlinear refractive index of 0.18?cm2?W−1 and find that the system shows exceptionally large optical nonlinearities, which are of potential fundamental and technological interest for quantum optics.
3,438 citations
References
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TL;DR: In this article, the first observation of radiation-pressure cooling on a system of resonant absorbers which are elastically bound to a laboratory fixed apparatus was reported, and they were cooled to 40 K by irradiating them with the 8-ensuremath{\mu}W output of a frequency doubled, single-mode dye laser tuned to the low-frequency side of the Doppler profile on the $S 2S 1/2
Abstract: We report the first observation of radiation-pressure cooling on a system of resonant absorbers which are elastically bound to a laboratory fixed apparatus. Mg ii ions confined in a Penning electromagnetic trap are cooled to 40 K by irradiating them with the 8-\ensuremath{\mu}W output of a frequency doubled, single- mode dye laser tuned to the low- frequency side of the Doppler profile on the $^{2}S_{\frac{1}{2}}\ensuremath{\leftrightarrow}^{2}P_{\frac{3}{2}}$ (${M}_{J}=+\frac{1}{2}\ensuremath{\leftrightarrow}{M}_{J}=+\frac{3}{2}$ or ${M}_{J}=\ensuremath{-}\frac{1}{2}\ensuremath{\leftrightarrow}{M}_{J}=\ensuremath{-}\frac{3}{2}$) transitions. Cooling to approximately ${10}^{\ensuremath{-}3}$ K should be possible.
556 citations
"Observation of Bose-Einstein Conden..." refers background in this paper
...Of the three or four most prominent players in the development of laser cooling, two (David Wineland and Bill Phillips) are long-standing Bureau scientists; two of their most influential papers are described in this volume [6,7]....
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TL;DR: In this article, phonon-like excitations of a Bose-Einstein condensate (BEC) in a dilute atomic gas were observed, and they were found to persist longer than their counterparts in uncondensed clouds.
Abstract: We observe phononlike excitations of a Bose-Einstein condensate (BEC) in a dilute atomic gas. ${}^{87}$Rb atoms are optically trapped and precooled, loaded into a magnetic trap, and then evaporatively cooled through the BEC phase transition to form a condensate. We excite the condensate by applying an inhomogeneous oscillatory force with adjustable frequency and symmetry. We have observed modes with different angular momenta and different energies and have studied how their characteristics depend on interaction energy. We find that the condensate excitations persist longer than their counterparts in uncondensed clouds.
531 citations
"Observation of Bose-Einstein Conden..." refers methods in this paper
...Within a year, these predictions were experimentally verified by the original NIST group in Boulder [13] and also by the group at MIT [14]....
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...A few months earlier, several groups (most notably the NIST/CU collaboration in Boulder, and groups at Rice University and at MIT) were very close to achieving Bose-Einstein condensation....
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...experimentally verified by the original NIST group in Boulder [13] and also by the group at MIT [14]....
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TL;DR: In this paper, a very cold sample of spin-polarized trapped atoms was produced, with an effective temperature as low as 1.2 K, which is the lowest kinetic temperature ever observed and far colder than any previous sample.
Abstract: We have produced a very cold sample of spin-polarized trapped atoms. The technique used dramatically simplifies the production of laser-cooled atoms. In this experiment, 1.8\ifmmode\times\else\texttimes\fi{}${10}^{7}$ neutral cesium atoms were optically captured directly from a low-pressure vapor in a small glass cell. We then cooled the 1-${\mathrm{mm}}^{3}$ cloud of trapped atoms and loaded it into a low-field magnetic trap in the same cell. The magnetically trapped atoms had an effective temperature as low as 1.1\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}K, which is the lowest kinetic temperature ever observed and far colder than any previous sample of trapped atoms.
507 citations
TL;DR: A new magneto-optical trap is demonstrated which confines atoms predominantly in a «dark» hyperfine level, that does not interact with the trapping light, that leads to much higher atomic densities as repulsive forces between atoms due to rescattered radiation are reduced and trap loss due to excited-state collisions is diminished.
Abstract: A new magneto-optical trap is demonstrated which confines atoms predominantly in a ``dark'' hyperfine level, that does not interact with the trapping light. This leads to much higher atomic densities as repulsive forces between atoms due to rescattered radiation are reduced and trap loss due to excited-state collisions is diminished. In such a trap, more than ${10}^{10}$ sodium atoms have been confined to densities approaching ${10}^{12}$ atoms ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$.
502 citations
TL;DR: The role of the centrifugal barrier in the final collision channel in reducing the loss of atoms from the trap due to transitions induced by the magnetic dipole-dipole interaction is discussed.
Abstract: We study the magnetic-field dependence of the cross sections for elastic and inelastic collisions of pairs of ultracold cesium atoms in a magnetic trap, calculated with the coupled-channels method. We pay special attention to atoms in the f=3, mf=-3 weak-field seeking state of the lower hyperfine manifold. The cross sections show a pronounced resonance structure. We discuss its origin, starting from the pure bound singlet and triplet rovibrational Cs2 states and introducing perturbations due to the hyperfine and Zeeman interactions. We also discuss the role of the centrifugal barrier in the final collision channel in reducing the loss of atoms from the trap due to transitions induced by the magnetic dipole-dipole interaction
484 citations