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Ancilla assisted calibration of a measuring apparatus



Alan L. Migdall, Giorgio Brida, L. Ciavarella, Ivo P. Degiovanni, Marco Genovese, M. G. Mingolla, M. G. A. Paris, Fabrizio Piacentini, Sergey Polyakov


The rapid development of quantum systems has enabled a wide range of novel and innovative technologies, from quantum information processing to quantum etrology and imaging [113], mainly based on optical systems. Precise characterization techniques of quantum resources, i.e. states [1421], operations [2225] and detectors [2629] play a critical role in development of such technolo- gies. In turn, the most reliable methods for quantum characterization rely on quantum properties of their resources, such as entanglement. Here we present the rst experimental characterization of quantum properties of an unknown detector, the reconstruction of its positive operator-valued measure (POVM), that takes advantage of a quantum resource, i.e. an ancillary state. In our experiment a POVM of a phase-insensitive photon-number-resolving detector is reconstructed with an accuracy that exceeds classical methods, while using no prior information about that detector. This is done by exploiting strong quantum correlations of twin beams generated by a parametric down conversion crystal: one beam is characterized by a quantum tomographer, while the other is used to calibrate the unknown detector. Our result opens a new page in a quantum detector characterization, that allows reconstruction of an inherently quantum measure of an arbitrary detector's performance -POVM - while explicitly providing an advantage over classical methods in accuracy, thus advancing quantum technologies.
Physical Review Letters


quantum information


Migdall, A. , Brida, G. , Ciavarella, L. , Degiovanni, I. , Genovese, M. , , M. , A., M. , Piacentini, F. and Polyakov, S. (2012), Ancilla assisted calibration of a measuring apparatus, Physical Review Letters, [online],, (Accessed April 17, 2024)
Created June 18, 2012, Updated May 27, 2021