Quantum tomography of light states by photon-number-resolving detectors

Abstract

We address state reconstruction by photon-number-resolving detectors, and demonstrate that they may be effectively exploited to perform quantum tomography of states of light. In particular, we find that the pattern function technique, originally developed for optical homodyne tomography, may be also applied to discrete data. Our results open new perspectives for quantum-state reconstruction in the mesoscopic regime, and pave the way to the use of photon-number-resolving-based detection schemes in Quantum Information science.

On the role of the local oscillator intensity in optical homodyne-like tomography

“…In Ref. [18], we have demonstrated that the probability distribution for the photon-number difference can be written in terms of the joint photon-number statistics q(m, n) measured at the two BS outputs:…”

“…The results obtained in Ref. [18] suggest that the intensity of the LO must be increased not only when the energy of the reconstructed states increases, but also when the states exhibit peculiar Wigner functions with, for instance, many oscillations in the phase space. In this last scenario, increasing the LO intensity allows a better sampling of the corresponding "discretized" homodyne probability distributions and, thus, a more faithful tomographic reconstruction.…”

“…In Ref. [18] we have shown the experimental reconstruction of classical states, such as coherent states and phase-averaged coherent states, obtained by means of hybrid photodetectors, which are commercial detectors endowed with partial photon-number resolution and a linear response up to 100 photons. One main limitation of this class of detectors is the quantum efficiency, which is roughly 50% in the green spectral region and can be further reduced in a realistic setup.…”

“…In Ref. [18] we have demonstrated that the scheme can be suitable for the reconstruction of both classical and nonclassical states of light (such as cat states), upon optimization of the value of the LO with respect to the signal state. The results obtained in Ref.…”

Exploiting the wide dynamic range of silicon photomultipliers for quantum optics applications

“…Through this analysis, we also study the limits imposed by nonlinearities and saturation effects of some parts of the acquisition chain, having in mind the exploitation of the high dynamic range of SiPMs to detect well-populated states of light. Indeed, reliably detecting the number of photons in every pulse of highly-populated states is the key resource to implement homodyne-like schemes with a mesoscopic local oscillator (up to 50 mean photon numbers), as required to achieve an optimal quantum state reconstruction [8,9]. Increasing the dynamic range is also required if the considered states of light are characterized by large fluctuations, such as in the case of superthermal states of light [10,11].…”