MultiPhoton Quantum Interferometry
Abstract
Based on the investigation of multiphoton entanglement, as produced by stimulated parametric downconversion, a technique is presented to create heralded ``noon'' states. The relevance for interferometry will be discussed. Furthermore we explored the use of photonnumber resolving detectors in MachZehnder type of interferometers. Our current detectors can distinguish 0, 1, 2, to7, photon impacts. Although the overall collection and detection efficiency of photons is well below unity (about 0.3) the photon number resolving property is still very useful if combined with coherent input states since those state are eigenstates of the photon annihilation operator. First we analyze the coherent state interferometer with a single photonnumber resolving detector, revealing the strong nonlinear response of an interferometer in the case of Fockstate projection. Second, we use two such detectors together with a Baysian phase estimation strategy to demonstrate that it is possible to achieve the standard quantum limit independently from the true value of the phase shift. This protocol is unbiased and saturates the CramerRao phase uncertainty bound and, therefore, is an optimal phase estimation strategy. As a final topic it will be shown how quantum interferometry combined with micromechanical structures can be used to investigate quantum superpositions and quantum decoherence of macroscopic objects.
 Publication:

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts
 Pub Date:
 June 2007
 Bibcode:
 2007APS..DMP.G2001B