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Cretan Matter Waves Papers

- Time-Averaged Adiabatic Potentials: Versatile traps and waveguides for ultracold quantum gases
Igor Lesanovsky and Wolf von Klitzing
Phys. Rev. Lett. 99, 083001 (2007) (link)
(cond-mat/0612213 abs(v1), more recent version: pdf(v2))

In this paper we describe one of the key techniques that we are going to use to construct the ring-shaped wave-guide for our matter-wave interferometer. We use RF-magnetic fields to 'dress' the atoms and then lower frequency magnetic fields to time-average them. The so-called time-averaged adiabatic potentials (TAAP) can be used to make traps of a great variety of shapes: pancake-, cigar-, sickle-, and ring- shapes. Using multiple RF-frequencies at the same time, we can create multiple traps, which can be dynamically split or combined simply by tuning the frequencies and amplitudes of the magnetic fields applied.

The main advantages of the TAAP lie on one hand in the complexity of the traps that can be created, on the other hand in the enormous flexibility: The shape of the traps depends only on the amplitudes, frequencies and phases of the applied magnetic fields, which are readily controlled by a computer.

- Spontaneous emergence of angular momentum Josephson oscillations in coupled annular Bose-Einstein condensates
I. Lesanovsky and W. von Klitzing
Phys. Rev. Lett. 98, 050401 (2007)
(pdf, abs, quant-ph)

Here we look at what happens if one couples two condensates in separate ring-shaped traps. At first one sees Josephson oscillations of the atom numbers between the two rings. The chemical potential of the condensates causes a non-linearity, which tries to smooth out any density fluctuations. We show by numerical simulation that for long evolution times this results in counter-propagating super-currents in the two rings, thus breaking the initial chiral symmetry of the BECs. Due to the ongoing tunneling these super-currents periodically change directions. Hence the title: angular momentum Josephson oscillations