arXiv subjects

Andrea Cavanna

Publications and source records attributed to Andrea Cavanna.

9 recordsLinked to original sources

arXiv2020

Reconstructing 2D spatial modes for classical and quantum light

We propose a method for finding 2D spatial modes of thermal field through a direct measurement of the field intensity and an offline analysis of its spatial fluctuations. Using this method, in a simple and efficient way we reconstruct the modes of a multimode fiber and the spatial Schmidt modes of squeezed vacuum generated via high-gain parametric down conversion. The reconstructed shapes agree with the theoretical results.

quant-ph↗

arXiv2019

Towards third-order parametric down-conversion in optical fibers

Optical fibers have been considered an optimal platform for third-order parametric down-conversion since they can potentially overcome the weak third-order nonlinearity by their long interaction length. Here we present, in the first part, a theoretical derivation for the conversion rate both in the case of spontaneous generation and in the presence of a seed beam. Then we review three types of optical fibers and we examine their properties in terms of conversion efficiency and practical feasibility.

quant-ph↗

arXiv2018

Seeded and unseeded high order parametric down conversion

Spontaneous parametric down conversion (SPDC) has been one of the foremost tools in quantum optics for over five decades. Over that time it has been used to demonstrate some of the curious features that arise from quantum mechanics. Despite the success of SPDC, its higher-order analogues have never been observed, even though it has been suggested that they generate far more unique and exotic states than SPDC. An example of this is the emergence of non-Gaussian states without the need for post-selection. Here we calculate the expected rate of emission for nth-order SPDC with and without external stimulation (seeding). Focusing primarily on third-order parametric down-conversion (TOPDC), we estimate the photon detection rates in a rutile crystal, for both the unseeded and seeded regimes.

quant-ph↗

arXiv2018

Multiphoton nonclassical light from clusters of single-photon emitters

We study nonclassical features of multiphoton light emitted by clusters of single-photon emitters. As signatures of nonclassicality, we use violation of inequalities for normalized correlation functions of different orders or the probabilities of multiphoton detection. In experiment, for clusters of 2 to 14 colloidal CdSe/CdS dot-in-rods we observe nonclassical behavior, which gets even more pronounced for larger clusters.

quant-ph↗

arXiv2015

Tunable optical parametric generator based on the pump spatial walk-off

We suggest a novel optical parametric generator (OPG) in which one of the down-converted beams is spontaneously generated along the Poynting vector of the pump beam. In this configuration, the generation takes advantage of the walk-off of the extraordinary pump rather than being degraded by it. As a result the generated beams, signal and idler, are bright, due to a high conversion efficiency, spatially nearly single-mode, due to the preferred direction of the Poynting vector, tuneable over a wide range of wavelengths, and broadband. The two beams are also correlated in frequency and in the photon number per pulse. Furthermore due to their thermal statistics these beams can be used as a pump to efficiently generate other nonlinear processes.

quant-ph↗

arXiv2014

Detection of non-classical space-time correlations with a novel type of single-photon camera

During the last decades, multi-pixel detectors have been developed capable of registering single photons. The newly developed Hybrid Photon Detector camera has a remarkable property that it has not only spatial but also temporal resolution. In this work, we use this device for the detection of non-classical light from spontaneous parametric down-conversion and use two-photon correlations for the absolute calibration of its quantum efficiency.

physics.ins-det↗

arXiv2014

Compensation of anisotropy effects in the generation of two-photon light

We analyse a method to compensate for anisotropy effects in the spatial distribution of parametric down-conversion (PDC) radiation in bulk crystals. In this method, a single nonlinear crystal is replaced by two consecutive crystals with opposite transverse walk-off directions. We implement a simple numerical model to calculate the spatial distribution of intensity and correlations, as well as the Schmidt mode structure, with an account for the anisotropy. Experimental results are presented which prove the validity of both the model and the method.

quant-ph↗

arXiv2013

Transverse Entanglement of Biphotons

We measure the transverse entanglement of photon pairs on their propagation from the near to the far field of spontaneous parametric downconversion (SPDC). The Fedorov ratio, depending on the widths of conditional and unconditional intensity measurements, is shown to be only able to characterize entanglement in the near and far field zones of the source. Therefore we also follow a different approach. By evaluating the first-order coherence of a subsystem of the state we can quantify its entanglement. Unlike previous measurements, which determine the Fedorov ratio via intensity correlations, our setup is sensitive to both phase and modulus of the biphoton state and thus always grants experimental access to the full transverse entanglement of the SPDC state. It is shown theoretically that this scheme represents a direct measurement of the Schmidt number.

quant-ph↗

arXiv2011

Experimental realization of Counterfactual Quantum Cryptography

In counterfactual QKD information is transfered, in a secure way, between Alice and Bob even when no particle carrying the information is in fact transmitted between them. In this letter we fully implement the scheme for counterfactual QKD proposed in [T. Noh, \PRL \textbf{103}, 230501 (2009)], demonstrating for the first time that information can be transmitted between two parties without the transmission of a carrier.

quant-ph↗