September 2013

 

Abstracts of the QSIT Lunch Seminar, Sept 5, 2013

Sympathetic cooling of a micromechanical membrane by coupling to ultracold atoms

Tobias Kampschulte, Quantum atom optics lab, University of Basel

In the field of optomechanics, radiation pressure forces exerted by laser beams are exploited to cool and control the vibrational state of mechanical oscillators. Recently, even the quantum level has been reached [1,2]. This points towards studying quantum physics with macroscopic objects, or applications in precision force sensing. On the other hand, lasers are a well-established tool to control both the motional and internal states of atoms in a gas.

Using a laser beam to couple the motion of a macroscopic membrane to an ensemble of ultracold atoms forms the basis of a hybrid quantum system [3]. There, the atoms could be used to read out the motion of the oscillator, to engineer its dissipation, and ultimatively to perform quantum information tasks such as coherently exchanging the quantum states of the two systems.

We realize such a hybrid system by trapping ultracold rubidium atoms in an optical lattice formed by a laser beam which is retro-reflected by a micromechanical silicon nitride membrane [3,4]. The mutual coupling of the two systems is demonstrated in an sympathetic cooling experiment, where the  damping of the membrane motion is increased and its steady-state amplitude is reduced when it is coupled to laser-cooled atoms.).

In collaboration with: Aline Faber, Andreas Jöckel, Maria Korppi, Thomas Lauber, Matthew Rakher and Philipp Treutlein

References:

[1]  R. Rivière et al., Phys. Rev. A 83, 063835 (2011)
[2]  J. Chan et al., Nature 478, 89 (2011)
[3]  S. Camerer et al., Phys. Rev. Lett 107, 223001 (2011)
[4]  B. Vogell et al.,  Phys. Rev. A 87, 023816 (2013)

Ultracold Rydberg atoms: from atomic hyperfine-structure to many-body interactions

Johannes Deiglmayr, Molecular Physics and Spectroscopy, ETH Zurich

The study of dense samples of ultracold atoms in high Rydberg states has yielded many spectacular results in recent years, such as the observation of exotic dimers with bond-lengths exceeding one micrometer or the realization of quantum gates based on neutral atoms [1]. We have recently setup an experiment which allows us to study transitions between Rydberg states by high-resolution millimeter-wave spectroscopy under conditions where the stray electric and magnetic fields are reduced to below 1 mV/cm and 2 mG, respectively. Measurements of the hyperfine-splitting of atomic Rydberg states with principal quantum number beyond n=100, showing transform-limited linewidths of better than 20 kHz, demonstrated the performance of the setup [2].

Recently we added an optical dipole trap to the setup to investigate the Rydberg excitation in denser samples of ultracold atoms. We have observed the excitation of dipole-forbidden pair-states, which we attribute to the formation of so called "macro dimers" [3].

References:

[1] Bendkowsky et al., Nature 458 (2009); Isenhower et al., PRL 104 (2010); Wilk et al., ibid
[2] H. Sassmannshausen, F. Merkt, J. Deiglmayr, Phys. Rev. A 87, 032519 (2013)
[3] S.M. Farooqi, et al., Phys. Rev. Lett. 91, 183002 (2003)

 

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