We demonstrate theoretically and experimentally the phenomenon of vibrational resonance in a periodic potential, using cold atoms in an optical lattice as a model system. A high-frequency (HF) drive, with a frequency much larger than any characteristic frequency of the system, is applied by phase modulating one of the lattice beams. We show that the HF drive leads to the renormalization of the potential. We used transport measurements as a probe of the potential renormalization. The very same experiments also demonstrate that transport can be controlled by the HF drive via potential renormalization.

One path to realizing systems of trapped atomic ions suitable for large-scale quantum computing and simulation is to create a two-dimensional (2D) array of ion traps. Interactions between nearestneighbouring ions could then be turned on and off by tuning the ions' relative positions and frequencies. We demonstrate and characterize the operation of a planar-electrode ion-trap array. By driving the trap with a network of phase-locked radio-frequency resonators which provide independently variable voltage amplitudes we vary the position and motional frequency of a Ca + ion in two-dimensions within the trap array. Work on fabricating a miniaturised form of this 2D trap array is also described, which could ultimately provide a viable architecture for large-scale quantum simulations. means, linear arrays of ion traps have been demonstrated and ions in separate wells have been entangled [11]. The situation in a 2D array of traps, however, is more complicated as the ions are confined in at least two (and possibly three) directions by a pseudopotential created by a radio-frequency (RF) field. Sophisticated efforts to create a 2D array of linear ion traps whereby the ions are shuttled through junctions [4,14] have constituted an active area of research. Here, a method is investigated to vary the inter-ion spacing in a 2D array of point ion traps [15], while keeping the ions at their respective RF nulls.There have been experimental demonstrations of confining ions in a 2D array of point ion traps [16]. And the first realization of a 2D array of point traps on a microchip was able to demonstrate the ability to transfer ions between sites [17]. Chiaverini and Lybarger [18,19] have proposed dynamically re-configurable arrays in which RF electrode 'pixels' could be switched on or off. We have proposed an extension of the basic 2D array architecture by which the RF electrodes are segmented, allowing the positions and frequencies of trapped ions in a 2D array to be tuned by varying RF voltages [15]. As the RF voltage on a particular electrode is reduced, the electric field above that electrode falls, and the ion moves towards the region of reduced electric field. This is then analogous to the tuning of ions' positions and frequencies in a 1D array by varying DC voltages, though it allows the tuning to be done in both directions of the 2D array.There are a number of methods which may be used to apply RF voltages of different amplitudes to different electrodes, and thereby control the position of the RF null. At low frequencies, dust traps holding lycopodium spores have been reconfigured using variable alternating voltages of 50 Hz [15]. In ion traps, different electrodes can be driven with different amplitude voltages by utilizing different tapping points in a single helical resonator [20]. The RF null has also been moved in a more smoothly continuous fashion by selectively adjusting the load capacitance of the trap electrodes [21,22]. This latter method has been used to switch between trapping configurations in which ions were in...

Infinite densities can describe the long-time properties of systems when ergodicity is broken and the equilibrium Boltzmann-Gibbs distribution fails. We here perform semiclassical Monte Carlo simulations of cold atoms in dissipative optical lattices with realistic parameters. We show that the momentum infinite density, as well as its scale invariance, should be observable in shallow potentials. We further evaluate the momentum autocorrelation function in the stationary and aging regime.

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