Experimental tests of quantum nonlinear dynamics in atom optics

Sigurd Dyrting, Wenyu Chen, Gerard J Milburn

W. K. Hensinger, N. R. Heckenberg, Gerard J Milburn +1 more

S. L. Rolston, William D. Phillips

W. K. Hensinger, N. R. Heckenberg, Gerard J Milburn +1 more

Cold atoms in optical potentials provide an ideal test bed to explore quantum nonlinear dynamics. Atoms are prepared in a magneto-optic trap or as a dilute Bose–Einstein condensate and subjected to a far detuned optical standing wave that is modulated. They exhibit a wide range of dynamics, some of which can be explained by classical theory while other aspects show the underlying quantum nature of the system. The atoms have a mixed phase space containing regions of regular motion which appear as distinct peaks in the atomic momentum distribution embedded in a sea of chaos. The action of the atoms is of the order of Planck’s constant, making quantum effects significant. This tutorial presents a detailed description of experiments measuring the evolution of atoms in time-dependent optical potentials. Experimental methods are developed providing means for the observation and selective loading of regions of regular motion. The dependence of the atomic dynamics on the system parameters is explored and distinct changes in the atomic momentum distribution are observed which are explained by the applicable quantum and classical theory. The observation of a bifurcation sequence is reported and explained using classical perturbation theory. Experimental methods for the accurate control of the momentum of an ensemble of atoms are developed. They use phase space resonances and chaotic transients providing novel ensemble atomic beamsplitters. The divergence between quantum and classical nonlinear dynamics is manifest in the experimental observation of dynamical tunnelling. It involves no potential barrier. However a constant of motion other than energy still forbids classically this quantum allowed motion. Atoms coherently tunnel back and forth between their initial state of oscillatory motion and the state 180 ° out of phase with the initial state.

Tommaso Francalanci, Giovanni Rodari, Eugenio Caruccio +11 more

To assess the capabilities of photonic quantum systems, it is essential to develop analytical and experimental methods for probing the underlying optical dynamics. Here, we investigate fundamental constraints arising when multi-photon states evolve through a quantum linear optical network, showing how such limitations can be overcome when introducing measurement-induced nonlinearities. Specifically, we analyze bounds related to photon-bunching behavior at the output of a linear interferometer and test them via a hybrid photonic platform realizing experiments with up to four photons. When the analysis is extended to a nonlinear regime, such bounds can be violated. We experimentally validate such behavior by employing an optical architecture featuring measurement-induced nonlinearity, thus introducing dynamics that go beyond standard linear optics. Our results highlight how the constraints implied by the linear optical formalism can be used as tools to test and characterize photonic models going beyond quantum linear optical dynamics.

Windell H. Oskay