Quantum Optics Seminar by Romain Quidant – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Romain Quidant

Extensive research in Nano-optics over the last decade has made possible controlling optical fields on the nanometer scale. Such concentration of light, well below the limit of diffraction, opens plenty of new routes towards enhanced interaction with tiny amounts of matter down to the single molecule/atom level. In this talk we will present our recent advances in enhanced light-matter interaction on the nanometer scale and their applications to quantum optics. 

The first part of the talk focuses on our recent work on the controlled interaction of Nitrogen Vacancy (NV) centers with nano-optical structures. We first discuss an approach in which light is used to trap and manipulate a single nanodiamond containing a single NV. We demonstrate both translational and angular control of the trapped NV and discuss applications to vectorial magnetometry and mapping of the electromagnetic local density of states [1]. In a second step, our manipulation technique is applied to deterministically locate single nano-diamonds in the hot spot of plasmonic antennas [2]. The interaction of the immobilized NV with the nano-antenna is quantified by analyzing the change in its fluorescence lifetime. Last but not least we demonstrate that the hybrid system formed by a single NV coupled to a gold gap antenna can operate as an efficient and fast optical switch upon non-resonant CW illumination. We show a modulation of the NV fluorescence by more than 80% with time response faster than 100ns that we control through an independent NIR gating laser of a few mW [3]. 

The second part of the talk presents our latest advances in optomechanics. We optically trap a single nanoparticle in high vacuum and cool its three spatial degrees of freedom by means of active parametric feedback. Using a single laser beam for both trapping and cooling we demonstrate a temperature compression ratio of four orders of magnitude. We discuss the potential of this approach for ground state cooling at room temperature [4]. Besides center-of-mass cooling, the ultra-high mechanical quality factor of a levitating nanoparticle (108 at 10-6mbar) offers great opportunities for ultra-sensitive metrology. We show that thermal energy suffices to drive the oscillator motion in its nonlinear regime. The achieved force sensitivity of 20 zN.Hz−1/2, which is the highest value reported so far at room temperature, is sufficient to sense ultraweak interactions, such as non-Newtonian gravity-like forces [5]. 

[1] M. Geiselmann, M. L. Juan, J. Renger, J. M. Say, L. J. Brown, F. J. García de Abajo, F. Koppens, R. Quidant, Nature Nanotechnol. 8, 175-179 (2013)
[2] M. Geiselmann, R. Marty, F. J. García de Abajo, R. Quidant, Nano Lett. 14, 1520-1525 (2014)
[3] M. Geiselmann, R. Marty, F. J. García de Abajo, R. Quidant, Nature Phys. 9, 785-789 (2013)
[4] J. Gieseler, B. Deutsch, R. Quidant, L. Novotny, Phys. Rev. Lett. 109, 103603 (2012)
[5] J. Gieseler, L. Novotny, R. Quidant , Nature Phys. 9, 806-810 (2013)