Robust spatial coherence 5 μ\,\mum from a room-temperature atom chip

We study spatial coherence near a classical environment by loading a Bose-Einstein condensate into a magnetic lattice potential and observing diffraction. Even very close to a surface (5$\,\mu$m), and even when the surface is at room temperature, spatial coherence persists for a relatively long time ($\ge$500$\,$ms). In addition, the observed spatial coherence extends over several lattice sites, a significantly greater distance than the atom-surface separation. This opens the door for atomic circuits, and may help elucidate the interplay between spatial dephasing, inter-atomic interactions, and external noise.Comment: 15 pages, 14 figures, revised for final publication. This manuscript includes in-depth analysis of the data presented in arXiv:1502.0160

The Faraday Quantum Clock and Non-local Photon Pair Correlations

We study the use of the Faraday effect as a quantum clock for measuring traversal times of evanescent photons through magneto-refractive structures. The Faraday effect acts both as a phase-shifter and as a filter for circular polarizations. Only measurements based on the Faraday phase-shift properties are relevant to the traversal time measurements. The Faraday polarization filtering may cause the loss of non-local (Einstein-Podolsky-Rosen) two-photon correlations, but this loss can be avoided without sacrificing the clock accuracy. We show that a mechanism of destructive interference between consecutive paths is responsible for superluminal traversal times measured by the clock.Comment: 6 figure

Using time reversal symmetry for sensitive incoherent matter-wave Sagnac interferometry

We present a theory of the transmission of incoherent guided matter-waves through Sagnac interferometers. Interferometer configurations with only one input and one output port have a property similar to the phase rigidity observed in the transmission through Aharonov-Bohm interferometers in coherent mesoscopic electronics. This property is connected to the existence of counterpropagating paths of equal length and enables the operation of such matter-wave interferometers with incoherent sources. High finesse interferometers of this kind have a rotation sensitivity inversely proportional to the square root of the finesse