Quantum reading of digital memory with non-Gaussian entangled light

摘要

It has been shown recently S. Pirandola [Phys. Rev. Lett. 106, 090504 (2011)] that entangled light withnEinstein-Podolsky-Rosen correlations retrieves information from digital memory better than any classical light. Innidentifying this, a model of digitalmemory with each cell consisting of a reflecting medium with two reflectivitiesn(each memory cell encoding the binary numbers 0 or 1) is employed. The readout of binary memory essentiallyncorresponds to discrimination of two bosonic attenuator channels characterized by different reflectivities. Thenmodel requires an entire mathematical paraphernalia of a continuous variable Gaussian setting for its analysisnwhen arbitrary values of reflectivities 0 u0002 r0,r1 u0002 1 are considered. Here we restrict ourselves to a basic quantumnreadout mechanism with two different families of non-Gaussian entangled states of light, in which the binarynchannels to be discriminated are (i) ideal memory characterized by reflectivity r1 = 1 (identity channel) and (ii) anthermal noise channel—where the signal light illuminating the memory location gets completely lost (r0 = 0) andnonly a white thermal noise hitting the upper side of the memory reaches the decoder. We compare the quantumnreading efficiency of two families of non-Gaussian entangled light [(m,mu0002) family of path-entangled photonnstates and entangled state obtained by mixing a single photon with coherent light in a 50:50 beam splitter] withnany classical source of light in this model. We identify that the classes of non-Gaussian entangled transmittersnstudied here offer significantly better reading performance than any classical transmitters of light in the regimenof low signal intensity. We also demonstrate that the (m,mu0002) family of entangled light exhibits better readingnperformance than NOON states.