Brownian ratchets in cold atom dissipative lattices

Presenting Author: Alexander Staron, Miami University
Contributing Author(s): Ajithamithra Dharmasiri, Anthony Rapp, Samir Bali

Natural biological machines significantly outperform artificial nanodevices by efficiently harnessing energy from random noise/fluctuations. Dissipative optical lattices are ideal for elucidating mechanisms to optimize efficiency in artificial nanomachines, with the goal of rivaling biomolecular motors. We reduce the complicated problem of biomolecular ratchets to three basic conditions – there must be present in the system random noise, asymmetry, and non-equilibrium. We show how these conditions can be analyzed in dissipative optical lattices in terms of three distinct frequencies – the photon scattering rate (a measure of the noise), the vibrational frequency of atoms oscillating at the bottoms of potential wells of the lattice (a measure of the symmetry of the confining potential), and the driving frequency at which the potential wells are modulated (a measure of the asymmetry, and also non-equilibrium, introduced). We show experimentally that by shining an additional probe laser beam onto a tetrahedral 3D dissipative optical lattice we introduce a propagating modulation that forms a ratchet for a specific velocity-class of atoms. We distinguish between “stochastic resonance” where the vibrational frequency of the confined atoms is brought into resonance with the photon scattering rate, and “resonant activation” where the asymmetrizing driving frequency is brought into resonance with the vibrational frequency. We show that our ratchet is an example of resonant activation.

(Session 5 : Sunday from 5:00pm - 7:00pm)


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