Ultra-sensitive atom imaging for matter-wave optics

Pappa, Melina; Condylis, Paul C.; Konstantinidis, G.; Bolpasi, Vasiliki; Lazoudis, Angelos; Morizot, Olivier; Sahagún, Daniel; Baker, Mark; Klitzing, Wolf von

doi:10.1088/1367-2630/13/11/115012

Cited by 32 publications

(41 citation statements)

References 21 publications

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“…In the context of ultra-cold atoms and Bose-Einstein condensation (BEC), where the spatial distribution of atoms reveals most of the important physics, absorption imaging is the most commonly used technique. Recently, diffractive dark-ground imaging has been demonstrated as a novel ultra-sensitive technique to image very small ultra-cold atom sample [6].…”

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confidence: 99%

“…Ref. [6] provides a detailed analysis of the atom numbers detected using dark-ground and absorption imaging. In an experimental comparison between the two methods they found good agreement.…”

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confidence: 99%

“…due to molecular association, resulting in samples which are far too small for standard absorption imaging techniques. We therefore employ dark-ground imaging-a novel ultra sensitive absorption imaging technique [6]. For each data-point, we determine the number of atoms from an image of the fluorescence of the atoms in the MOT, release the atoms, and take the dark-ground imaging sequence of the very same atom sample.…”

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confidence: 99%

“…This reduces the noise from the large background of the probe light, thus enabling us to image atom clouds with only 100 atoms at optical depths 1 down to OD = 0 01 using an exposure time of 100 µs. The principles of diffractive dark-ground imaging are described in [6]. Fig.…”

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Atom number calibration in absorption imaging at very small atom numbers

Konstantinidis¹,

Pappa²,

Wikström

et al. 2012

Open Physics

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Abstract:Cold atom experiments often use images of the atom clouds as their exclusive source of experimental information. The most commonly used technique is absorption imaging, which provides accurate information about the shapes of the atom clouds, but requires care when seeking the absolute atom number for small atom samples. In this paper, we present an independent, absolute calibration of the atom numbers. We directly compare the atom number detected using dark-ground imaging to the one observed by fluorescence imaging of the same atoms in a magneto-optical trap. We normalise the signal using single-atom resolved fluorescence imaging. In order to be able to image the absorption of the very low atom numbers involved, we use diffractive dark-ground imaging as a novel, ultra-sensitive method of in situ imaging for untrapped atom clouds down to only 100 atoms. We demonstrate that the Doppler shift due to the acceleration of the atoms by the probe beam has to be taken into account when measuring the atom-number.PACS (2008) Cold atom experiments extract most of their experimental information from images of freely expanding atom clouds. *

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Atom number calibration in absorption imaging at very small atom numbers

Konstantinidis¹,

Pappa²,

Wikström

et al. 2012

Open Physics

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“…However, in the future there is the intention to utilise dark-ground imaging techniques, new to Bose-Einstein condensates, to image condensates to very low atom numbers. Recently, numbers as low as 7 have been resolved [179], as well as in-situ imaging [180] using the darkground technique. By inserting a mask in front of a collecting lens only light scattering by atoms is collected and any background light does not reach the detector.…”

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Design, construction, and performance towards a versatile 87Rb and 41K BEC apparatus

Parry¹

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The possibility to mould and control pure quantum systems has been offered by the experimental observation of Bose-Einstein condensation, a unique phase of matter when macroscopic quantities of a gas occupy the lowest quantum state.Techniques for creating these degenerate gases vary from laboratory to laboratory; each offers an unique test bed for studying quantum physics on a macroscopic scale.This thesis reports on the experimental design, construction and performance of an apparatus to create two-component 87 Rb and 41 K condensates for studies of non-equilibrium dynamics.This thesis is broken down as follows. In Chapter 1, a brief overview of the history and status of Bose Einstein condensates is presented, to affirm the motivation behind our work. Chapter 2 then presents the fundamental theory and background information to understand how and why our experiment was built.Chapter 3 describes the bulk of the work undertaken at the beginning of this thesis. In particular it describes the design choices, construction and performance of the vacuum, and laser and magnetic coil systems that are the key structural elements of the apparatus. In particular the vacuum system is a two-component differentially pumped system designed to optimise the number and lifetime of trapped atoms. Another integral element of the vacuum chamber is the science cell that enables high optical access, and close physical, access to an atomic cloud.As a result, high resolution imaging, 980 nm resolution at 780 nm is expected with a commercial microscope objective lens. The laser system is carefully designed to best combine and deliver the seven different optical frequencies required to simultaneously trap and manipulate 87 Rb and 41 K atoms. The magnetic coil system also represents an integral component of the apparatus, responsible for trapping and transferring atoms in a quadrupole field. One pair of coils is able to have their current direction reversed in order to generate bias fields. This allows access to Feshbach resonances between the two species, once they have been iii condensed.

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Transport and Turbulence in Quasi-Uniform and Versatile Bose-Einstein Condensates

Gauthier¹

2020

Springer Theses

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Turbulence, motion characterized by chaotic changes in pressure and flow velocity, is a challenging problem in physics. However, its underlying properties are found to be universal and do not depend on the host fluid. Meanwhile, transport phenomena, irreversible exchange processes due to the statistical continuous random motion of particles, although being complicated from a microscopic point of view, can often be modelled quite simply by tracking macroscopic quantities of interest in the system. In this thesis, using atomic Bose-Einstein condensates, we study both these phenomena inside a quantum fluid using a highly configurable BEC platform developed to provide arbitrary dynamic control over the 2D superfluid system. Furthermore, the experiments are modelled using the Gross-Pitaevskii equation, the point vortex model and the hydrodynamic equations. After theoretical background and introduction to the apparatus, the technique of direct imaging of a digital micromirror device is described, which achieves the highly versatile and dynamic 2D potentials that facilitate the experimental studies described. Superfluid transport through a mesoscopic channel of tuneable length and width is next described. By investigating low amplitude oscillations and their dependence on the system parameters, a resistor, capacitor, and inductor model is used to model the transport. Surprisingly, the "contact inductance" of the channel at the reservoirs is a dominant effect for a significant portion of the parameter range. The resistive transport for high initial bias is also studied, showing an Ohmic resistive relationship over the broad parameter range. Next, the transport between two reservoirs initially prepared at different temperatures, but with similar particle number, was explored. Our 2D superfluid system, with hard-wall confinement, provides an ideal experimental system for the study of 2D quantum turbulence. The system is utilized to demonstrate the first experimental realization of large Onsager vortex clusters in the negative absolute temperature regime, through the injection of high energy clusters into the 2D superfluid. The clusters are found to be surprisingly stable for long time periods. The vortex cluster energy loss rate is studied while changing the system parameters, suggesting thermal damping is the dominant loss mechanism. The techniques and results presented in this thesis open up new avenues for the study of quantum fluids, be it by providing a concise atomtronic model for predicting superfluid transport or expanding the accessible parameters space available to fundamental studies of turbulence. The realization of negative temperature vortex distributions, long ago predicted by Onsager, open up the experimental study of the full phase-diagram of 2D vortex matter. The refinement of optical trapping techniques for BECs presents new and promising directions for future BEC experiments in configured potentials. This thesis is the culmination of many hours of work, to which a vast number of people contributed some ...

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Ultra-sensitive atom imaging for matter-wave optics

Cited by 32 publications

References 21 publications

Atom number calibration in absorption imaging at very small atom numbers

Atom number calibration in absorption imaging at very small atom numbers

Design, construction, and performance towards a versatile 87Rb and 41K BEC apparatus

Transport and Turbulence in Quasi-Uniform and Versatile Bose-Einstein Condensates

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