A study of bright matter-wave solitons of a cesium Bose-Einstein condensate (BEC) is presented. Production of a single soliton is demonstrated and dependence of soliton atom number on the interatomic interaction is investigated. Formation of soliton trains in the quasi one-dimensional confinement is shown. Additionally, fragmentation of a BEC has been observed outside confinement, in free space. In the end a double BEC production setup for studying soliton collisions is described. PACS numbers: 03.75.Lm, 67.85.Hj I. INTRODUCTION Non-dispersing wavepackets called solitons appear in many non-linear physical systems. Examples of solitons can be found in water waves [1], acoustic waves [2], light propagating through non-linear materials [3], plasmas [4], energy propagation along proteins [5], and many other systems including Bose-Einstein condensates (BECs) of cold atoms. Experimental research on solitons in BECs began with creation of a dark soliton [6, 7], followed by a bright soliton [8] and bright soliton trains [9]. Observation of more exotic gap solitons [10], decay of dark solitons into vortex rings [11], interactions between solitons [12-14], their interactions with impurities [15], optical potential barriers [16], speckle potentials [17] and demonstration of a matter-wave interferometer [18] show that a cold-atom BEC is an excellent and versatile system for studying solitons.Formation of solitons in a BEC depends on the twobody interaction between the atoms and the geometry of the trap used to confine the BEC. A quasi-onedimensional (quasi-1D) confinement is needed, which can be achieved in either magnetic or optical dipole traps. In such traps a dark soliton forms as a trough of lower density within a BEC with repulsive interatomic interaction while a bright soliton is a wavepacket comprising the whole BEC with attractive interatomic interaction that can move over macroscopic distances in a vacuum. So-called dark-bright solitons can be supported in twocomponent BECs, where atoms with one spin component fill the dark soliton within the BEC of the other spin component [13,19,20].Usually, only unchanging waves in one-dimensional integrable systems are called solitons. In quasi-1D harmonically confined geometry integrability is broken, but only slightly so. The solitary waves that form from BECs are three-dimensional objects, not one-dimensional, but their propagation is limited to one-dimension. The name soliton in this paper is used in its broader meaning com-
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.
The modulation of the interaction between the atoms in a matter-wave soliton in a quasi-onedimensional optical trap triggers an emission of correlated atom jets. We characterize the dependence of jet properties on the frequency, amplitude and length of the modulation, and qualitatively reproduce the trends in the mean-field picture with a one-dimensional time-dependent Gross-Pitaevskii equation simulation. High-order jets are observed for sufficiently long pulses, a double-pulse modulation sequence produces consecutive jets, and a multi-pulse sequence may lead to irregular jets at a finite angle to the direction of the channel. Finally, possible number squeezing of the jet pairs is investigated.
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