Creating Crystals to Study Quantum Effects

Emily Conover

Karmela Padavic-Callaghan

Josip Milanovic, Mikael Lassen, Michael Förtsch +3 more

Photonic crystal fibres (PCF) can be tailored to introduce a high effective nonlinear Kerr effect and to create lower amounts of excess noise compared to standard fibres. By exploiting both polarisation axes of the polarisation maintaining PCF we can generate two independent polarisation squeezed beams that can be used to create polarisation entanglement. We generated a maximum squeezing of-3.9 Aring plusmn 0.3 dB and a corresponding anti-squeezing of 16.8 Aring plusmn 0.3 dB. Furthermore we investigate the generation of polarisation squeezing in photonic crystal fibres by using a single pass setup where both the slow and fast axis has to be utilized. Taking advantage of these features and using ultrashort pulses we create polarisation squeezed states with notably higher purity than obtained in standard fibres.

Tobias Donner

Krzysztof Giergiel, Tien Tran, Ali Zaheer +4 more

Abstract We investigate the size of discrete time crystals s (ratio of response period to driving period) that can be created for a Bose–Einstein condensate (BEC) bouncing resonantly on an oscillating mirror. We find that time crystals can be created with sizes in the range s ≈ 20–100 and that such big time crystals are easier to realize experimentally than a period-doubling (s=2) time crystal because they require either a larger drop height or a smaller number of bounces on the mirror. We also investigate the effects of having a realistic soft Gaussian potential mirror for the bouncing BEC, such as that produced by a repulsive light-sheet, which is found to make the experiment easier to implement than a hard-wall potential mirror. Finally, we discuss the choice of atomic system for creating time crystals based on a bouncing BEC and present an experimental protocol for realizing big time crystals. Such big time crystals provide a flexible platform for investigating a broad range of non-trivial condensed matter phenomena in the time domain.

Marcel Spurny, Bill Corcoran, Christelle Monat +1 more

We discuss the enhancement of nonlinear functionalities in slow light photonic crystals. We show how slow light in photonic crystals is created, how nonlinear effects scale with the slowdown factor and what limits nonlinear effects in photonic crystals. We review some of the work recently reported in nonlinear optics in slow light photonic crystals and compare the observed effects to those found in other structures such as coupled resonators or photonic nanowires.