Nov 2020

Online symposium

In order to kick off an Indo-French co-funded collaboration [thanks to CEFIPRA] with the group of Prof. Shannon Whitlock in Strassbourg [link] involving "Quantum simulations of molecular energy transport", we will hold an online symposium on this topic on ZOOM, on Monday 30th Nov Tuesday 1st Dec, with the following program.

You can download the full resolution flyer above by clicking on the thumbnail. If you are interested
by 29th Nov (zoom link will only be send to email addressed collected in that form). We shall update this page with a link to the program shortly.

Oct 2020

Decoherence of Rydberg superpositions in BEC

Experiments can now excite Rydberg atoms within Bose-Einstein condensates [1]. We now completed a major body of work, providing the theoretical basis to deal with the decoherence of superpositions of different Rydberg electronic states in a BEC [2]. This extends our earlier work on Rydberg tracking (see below and [3]) to multiple internal states. We show that the Rydberg-in-BEC platform is a particularly nice open quantum system, in that it allows one to see both sides of the coin in a paradigmatic decohering spin: the loss of interference features in the system but also the system-environment entanglement that causes it [3].

April 2020

Quantum simulations: Rydberg atoms versus molecules

As discussed in [1] or [2] and here, interesting quantum simulation opportunities can be based on the fact that highly excited Rydberg atoms and complex bio-molecules share a similar mechanism allowing energy transport by dipole-dipole interactions, but in the former this remains pristinely quantum coherent [3], while in the latter it strongly suffers from decoherence through molecular vibrations [4].
We recently exploited the underlying analogy in two complementary directions: By porting the involved technique of two-dimensional spectroscopy that is used to explore molecular aggregates from the optical domain to that of micro-waves and Rydberg atoms [5] (left figure) and by showing that adiabatic excitation transport which we have shown prominently for mobile Rydberg atoms [6] may also be exploited in some particularly coherent molecular aggregates [7] (right figure).

March 2020

Theoretical physics via email

As the whole planet is in an exceptional state due to the virus, we are running a theoretical physics group via email. Thanks to all students and post-docs for keeping up their good work even under these difficult circumstances. On this occasion: You are at all the orange dots.

March 2020

Quantum soliton collisions

The collisions of solitons in Bose-Einstein condensates are an interesting example of quantum many-body dynamics, actively explored in experiments such as [1][2][3][4]. Over the years, there has been a mounting body of evidence [5][6][7] that commonly employed mean-field theory is not able to explain some essential feature of such experiments, such as an apparent predominance of repulsive interactions. Continuing these works, we recently demonstrated, that thermally accelerated phase diffusion can invalidate the mean-field picture before the onset of the first collisions, and then atom transfer during the collision then makes it even less applicable through the generation of mesoscopically entangled states [URL].

February 2020

From left to right: Sebastian Wüster, Gesa Schirren, Major of Dresden Dirk Hilbert,
Juana Mai and Dr. Nicola Mitwasi. Image (c) Jürgen Männel

Dresden Excellence Award

We are very grateful to the city of Dresden, Germany, for recognizing the interest of our research on quantum simulations with the "Dresden Excellence Award" for the year 2019, see here for more description (albeit in German). Thanks also to all past and present group-members and collaborators, without whom this would not have been possible.

April 2019

Rydberg bubble chambers

Rydberg excitation in BEC has become experimental state of the art [1], yet Rydberg and BEC physics largely remain separate due to the very different energy scales involved. Our recent work proposes to change that through a two stage process: (i) On the short time-scale (microseconds) of Rydberg physics one can create mobile impurities, which leave their mark on the host-BEC through inter-atomic collisions. (ii) The ensuing tracks are then turned into large signals by the much slower BEC response (milliseconds). This widely opens a new field of genuine Rydberg-BEC physics and provides a platform to explore just recently discovered ultra-cold inelastic reactions [2][3]. The whole idea is reminiscent of bubble chambers from the early days of particle physics (see above), where also a high(er) energy excitation leaves marks of their passing in the sourrounding medium. [URL]

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