Entangled two-photon fields: coherence, interference, and applications in quantum metrology

Abstract

Multi-particle coherence and entanglement are intimately related concepts. Although due to technological advancements many thought experiments of the last century aimed at investigating coherence and entanglement can now be performed, these concepts are still far from being fully understood. Nevertheless, the efforts to understand these concepts have led to several promising quantum information technologies. One of the physical processes in which the relations between coherence and entanglement has been extensively explored is spontaneous parametric down-conversion (SPDC)—a nonlinear optical process in which a pump photon interacts with a nonlinear crystal to produce a pair of entangled photons, termed as signal and idler. Using the PDC photons, two-photon coherence and entanglement effects have been observed in several degrees of freedom including polarization, time-energy, and position-momentum. This talk will present a brief overview of interference experiments performed with SPDC photons in the last few decades for investigating two-photon coherence and entanglement. These investigations have led to several promising technologies, and this talk will discuss some of these technologies that are in the domain of quantum metrology and imaging.