Paper detail

Quantum reading of digital memory with non-Gaussian entangled light

It has been shown recently (Phys. Rev. Lett. 106, 090504 (2011)) that entangled light with Einstein-Podolsky-Rosen (EPR) correlations retrieves information from digital memory better than any classical light. In identifying this, a model of digital memory with each cell consisting of reflecting medium with two reflectivities (each memory cell encoding the binary numbers 0 or 1) is employed. The readout of binary memory essentially corresponds to discrimination of two Bosonic attenuator channels characterized by different reflectivities. The model requires an entire mathematical paraphernalia of continuous variable Gaussian setting for its analysis, when arbitrary values of reflectivities are considered. Here we restrict to a basic quantum read-out mechanism with non-Gaussian entangled states of light, with the binary channels to be discriminated being ideal memory characterized by reflectivity one i.e., an identity channel and thermal noise channel, where the signal light illuminating the memory location gets completely lost (zero reflectivity) and only a white thermal noise hitting the upper side of the memory reaches the decoder. We compare the quantum reading efficiency of entangled light with any classical source of light in this model. We show that entangled transmitters offer better reading performance than any classical transmitters of light in the regime of low signal intensity.