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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Recent progresses at IENGF on studies on quantum information

G. Brida, E. Cagliero, Marco Genovese, Marco Gramegna, E. Predazzi

Published Aug 18, 2005• 0 citations
Publisher

Abstract

In this proceeding we present the most recent studies performed at IEN "Galileo Ferraris" on quantum information by using quantum optical states. After a general summary of the most recent studies, among them we will present in some details the results of two recent experiments. The first was addressed to tomographic reconstruction of a quantum state by using an innovative theoretical scheme based on a variable quantum efficiency of the detector. This scheme has been applied to Fock (PDC heralded photons), coherent (attenuated laser beam) and thermal states, for which experimental results will be presented. The second was pointed to experimentally investigate the effects of fibre propagation of PDC light produced in a type II crystal and, in particular, to the restoration of entanglement due to wave packet dispersion. Also in this case we will present and discuss our most recent data. Finally, we will shortly acknowledge of realisation of a heralded photon source with strong spectral selection.

DOI
10.1117/12.614874

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In this proceeding we present the most recent studies performed at IEN "Galileo Ferraris" on quantum information by using quantum optical states. After a general summary of the most recent studies, among them we will present in some details the results of two recent experiments. The first was addressed to tomographic reconstruction of a quantum state by using an innovative theoretical scheme based on a variable quantum efficiency of the detector. This scheme has been applied to Fock (PDC heralded photons), coherent (attenuated laser beam) and thermal states, for which experimental results will be presented. The second was pointed to experimentally investigate the effects of fibre propagation of PDC light produced in a type II crystal and, in particular, to the restoration of entanglement due to wave packet dispersion. Also in this case we will present and discuss our most recent data. Finally, we will shortly acknowledge of realisation of a heralded photon source with strong spectral selection.
In this proceeding I review the main experimental results obtained at IENGF (Turin, Italy) by using a source of entangled photons realised superposing, by means of an optical condenser, type I PDC produced in two crystals. More in details, after having described how this source is built, I will report on a Bell inequalities test obtained with it. Then I describe a recent innovative double slit experiment realised with a similar scheme. Finally, I hint about future developments of this activity at IENGF and in particular about a quantum cryptographic scheme in d=4.
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In this paper we will present some experimental researches about Quantum Communication performed in "Carlo Novero" Quantum Optics laboratory at INRiM (former IEN). After a general review of our studies, we will describe our recent researches on propagation of polarization entangled photons in optical fibres focused on the investigation of the effect of two-photon interference in the second-order Glauber's correlation function and on the characterization of this quantum channel as a Complete Positive (CP) map. We will then describe an innovative method, based on detectors operating in Geiger mode (on/off), for reconstructing the photon statistics of quantum optical states, presenting experimental data collected to test the extension of this method to multi-partite states.
Non-classical light is both easily encoded with quantum information and robust against decoherence, making it a key resource that enables many quantum information applications including quantum computing, quantum communication, and quantum metrology. We present a wide range of experimental and theoretical research toward the generation, detection, characterization, and storage of non-classical states of light with an eye toward quantum information applications. To provide a basis for the rest of the work, we begin by discussing theoretically the role of photon number statistics in optical quantum information and the use of second-order optical coherence to characterize non-classical light. Building on that, we present an original tool for the difficult problem of reconstructing the underlying mode distribution of multi-mode optical fields using simple measurements of higher-order optical coherence. We then move on to the problem of generating and storing single photons. We do this in a solid-state medium, a rare-earth ion-doped crystal, with a long-lived spin transition ideal for storing quantum information. We experimentally demonstrate the feasibility of this concept by showing correlations between the optical fields that herald storage and retrieval of collective excitations. This scheme can be used for the two important and distinct applications of generating single photons on-demand and storing quantum information and entanglement. The detection of non-classical light is a task as important as its generation. To this end, we study detectors with near unity detection efficiency and photon number resolution for use in quantum-enabled metrology. We use such a detector to experimentally demonstrate compression of spatial fringes and investigate the possibility of improving measurement resolution with classical and non-classical light. Finally, we report a set of experiments using photon number statistics to characterize classical and non-classical light. We measure suppression of unwanted multi-photon emission in a heralded single photon source based on four-wave mixing in microstructure optical fiber. And we, for the first time, experimentally demonstrate reconstruction of multi-mode classical and non-classical light from measured photon number statistics.
Here we report our recent experimental progresses in optical quantum information processing. In particular, the following topics are included. First, we extend the heralding scheme to multi-mode states and demonstrate heralded creation of qutrit states. Next, we demonstrate storage of single-photon states and synchronized release of them. Then, we demonstrate real-time acquisition of quadrature values of heralded states by making use of an exponentially rising shape of wave-packets. Finally, we demonstrate cluster states in an arbitrarily long chain in the longitudinal direction.