The Nonlocal Pancharatnam Phase in Two-Photon Interferometry

We propose a polarised intensity interferometry experiment, which measures the nonlocal Pancharatnam phase acquired by a pair of Hanbury Brown-Twiss photons. The setup involves two polarised thermal sources illuminating two polarised detectors. Varying the relative polarisation angle of the detectors introduces a two photon geometric phase. Local measurements at either detector do not reveal the effects of the phase, which is an optical analog of the multiparticle Aharonov-Bohm effect. The geometric phase sheds light on the three slit experiment and suggests ways of tuning entanglement.Comment: v3: final version to appear in Phys. Rev. A (Brief Reports

Atmospheric Neutrinos as a Probe of CPT Violation

We show that atmospheric neutrinos can provide a sensitive and robust probe of CPT violation (CPTV). We perform realistic event-rate calculations and study the variations of the ratio of total muon to antimuon survival rates with $L/E$ and $L$ ($L$ $\equiv$ baseline length, $E$ $\equiv$ neutrino energy) in a detector capable of identifying the muon charge. We demonstrate that measurements of these ratios when coupled with the significant $L$ and $E$ range which characterizes the atmospheric neutrino spectrum provides a method of both detecting the presence of such violations and putting bounds on them which compare very favourably with those possible from a future neutrino factory.Comment: 8 pages, 2 eps figures, modified version to appear in Phys. Lett.