Author Archives: Wolf von Klitzing

Bio info in admin

ELGAR featured in PhysicsWorld.com

Our ELGAR proposal to build a ground-based detector for Gravitational Waves has been featured in PhysicsWorld.com: “Physicists from across Europe have revealed plans for a huge underground gravitational-wave observatory that, if funded, could be operational by the mid-2030s. The European Laboratory for Gravitational and Atom-interferometric Research (ELGAR) could be located in either France or Italy and would cost around €200m to build. Those involved in the project have now applied for European funding to carry out a detailed design and costing for the facility.”

White paper on: Exploring the Foundations of the Universe with Space Tests of the Equivalence Principle

We have just published on https://arxiv.org/abs/1908.11785 a white paper on the scientific motivation for future space tests of the equivalence principle, to explore some of the big questions in physics (e.g. Equivalence Principle, Dark Matter and Gravitational Waves) using matter-wave interferometry, especially in space.

We discuss two possible mission scenarios, one based on quantum technologies, the other on electrostatic accelerometers, that could reach that goal are briefly discussed. We propose experiments to test the universality of free fall, at the level of 10−17 or better.

Download pdf

Precise and robust optical beam steering for space optical instrumentation

G. Drougakis, K. G. Mavrakis, S. Pandey, G. Vasilakis, K. Poulios, D. G. Papazoglou, and W. von Klitzing 
CEAS Space Journal (2019)
http://dx.doi.org/10.1007/s12567-019-00271-x
https://arxiv.org/abs/1907.10425

Abstract

This approach permits much finer adjustments of the beam direc- tion and position when compared to other beam steering techniques of the same mechanical precision. This results in a much increased precision, accu- racy and mechanical stability. A precision of better than 5μrad and 5 μm is demonstrated, resulting in a resolution in coupling efficiency of 0.1%. To- gether with the added flexibility of an additional beam steering element, this allows a great simplification of the design of the fiber coupler, which normally is the most complex and sensitive element on an optical fiber breadboard. We demonstrate a fiber to fiber coupling efficiency of more than 89.8%, with a stability of 0.2% in a stable temperature environment and 2% fluctuations over a temperature range from 10C to 40C over a measurement time of 14 hours. Furthermore, we do not observe any non-reversible change in the coupling efficiency after performing a series of tests over large temperature variations. This technique finds direct application in proposed missions for quantum experiments in space, e.g. where laser beams are used to cool and manipulate atomic clouds.

Saurabh will defend his thesis 12/7/2019

Πρόσκληση σε Δημόσια Παρουσίαση της Διδακτορικής Διατριβής του

κ. Saurabh Pandey

(Σύμφωνα με το άρθρο 41 του Ν. 4485/2017)

Την Παρασκευή 12 Ιουλίου 2019 και ώρα 10:00 στην αίθουσα Τηλεεκπαίδευσης στο κτήριο Τμήματος Μαθηματικών και Εφαρμοσμένων Μαθηματικών, Πανεπιστημίου Κρήτης, θα γίνει η δημόσια παρουσίαση και υποστήριξη της Διδακτορικής Διατριβής του υποψήφιου διδάκτορα του Τμήματος Επιστήμης και Τεχνολογίας Υλικών κ. Saurabh Pandey με θέμα:

«Guided Matter-Wave Interferometry»

Abstract:

Atom interferometry is an extremely sensitive and accurate means of measuring time, gravity, rotation, acceleration, magnetic gradients, and even fundamental physical constants. In particular for rotation sensing, these atomic systems are 10 billion times more sensitive than the optical gyroscopes, for an equal area of the interferometer loop. For practical applications such as satellite-free navigation, the ultracold atom based gyroscopes have to become portable and compact, without compromising their sensitivity.  This can be achieved by trapping and manipulation of ultracold atoms in smooth, area-enclosing waveguides. A major challenge, so far, has been the lack of ability to guide the trapped atomic wave-packets over long distances at relatively high speeds.

I will present excitation-free transport of Bose-Einstein condensates (BECs) at hypersonic speeds in magnetic time-averaged adiabatic potential (TAAP) rings traps. For the first time, matter-waves are transported for a record distance of 40 cm at hypersonic speeds without detecting any extra excitation when compared to the static case. The extreme smoothness of TAAP rings is demonstrated via the propagation of ultracold 87Rb atoms in ring waveguides. In addition, I studied atom optics with moving BECs in flat ring waveguides, to enable long distance guiding, and ultralow temperatures of the trapped atoms. I implemented an optimal cooling technique to achieve compact BEC guiding for seconds, and the effective BEC interaction energy was lowered by a factor of 30. These demonstrations provide a new platform to realize highly sensitive, miniaturized cold-atom-based gyroscopes, and investigate fundamental questions.

Our paper on the Fragility of the Laughlin states is accepted in PRA

preprint at arxiv.org (1810.07609) (pdf)

Abstract:
When a Bose-Einstein condensate rotates in a purely harmonic potential with an angular frequency which is close to the trap frequency, its many-body state becomes highly correlated, with the most well-known being the bosonic Laughlin state. To take into account that in a real experiment no trapping potential is ever exactly harmonic, we introduce an additional weak, quartic potential and demonstrate that the Laughlin state is highly sensitive to this extra potential. Our results imply that achieving these states experimentally is essentially impossible, at least for a macroscopic atom number.