Yuri D. van Nieuwkerk, Jörg Schmiedmayer, Fabian H. L. Essler
SciPost Phys. 5, 046 (2018) ·
published 8 November 2018

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We consider timeofflight measurements in split onedimensional Bose gases.
It is well known that the lowenergy sector of such systems can be described in
terms of two compact phase fields $\hat{\phi}_{a,s}(x)$. Building on existing
results in the literature we discuss how a single projective measurement of the
particle density after trap release is in a certain limit related to the
eigenvalues of the vertex operator $e^{i\hat{\phi}_a(x)}$. We emphasize the
theoretical assumptions underlying the analysis of "singleshot" interference
patterns and show that such measurements give direct access to multipoint
correlation functions of $e^{i\hat{\phi}_a(x)}$ in a substantial parameter
regime. For experimentally relevant situations, we derive an expression for the
measured particle density after trap release in terms of convolutions of the
eigenvalues of vertex operators involving both sectors of the twocomponent
Luttinger liquid that describes the lowenergy regime of the split condensate.
This opens the door to accessing properties of the symmetric sector via an
appropriate analysis of existing experimental data.
Fritz Diorico, Stefan Minniberger, Thomas Weigner, Benedikt Gerstenecker, Naz Shokrani, Zaneta Kurpias, Jorg Schmiedmayer
SciPost Phys. 4, 036 (2018) ·
published 22 June 2018

· pdf
The physics of superconducting films, and especially the role of remnant
magnetization has a defining influence on the magnetic fields used to hold and
manipulate atoms on superconducting atomchips. We magnetically trap ultracold
^{87}Rb atoms on a 200{\mu}m wide and 500nm thick cryogenically cooled niobium
Z wire structure. By measuring the distance of the atomcloud to the trapping
wire for different transport currents and bias fields, we probe the trapping
characteristics of the niobium superconducting structure. At distances closer
than the trapping wire width, we observe a different behaviour than that of
normal conducting wire traps. Furthermore, we measure a stable magnetic trap at
zero transport current. These observations point to the presence of a remnant
magnetization in our niobium film which is induced by a transport current. This
currentinduced magnetization defines the trap close to the chip surface. Our
measurements agree very well with an analytic prediction based on the critical
state model (CSM). Our results provide a new tool to control atom trapping on
superconducting atomchips by designing the current distribution through its
current history.
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