70 research outputs found
Quantum second harmonic generation in terms of elementary processes
We address the quantum dynamics of second harmonic generation with a
perturbative approach. By inspecting the Taylor expansion of the unitary
evolution, we identify the subsequent application of annihilation and creation
operators as elementary processes and find out how the expansion of the
second-harmonic photon-number probability distribution can be expressed in
terms of the interplay of these processes. We show that overlaps between the
output states of different elementary processes contribute to the expansion of
the probability distribution and provide a diagrammatic technique to
analytically retrieve terms of the distribution expansion at any order
Advances in Quantum Nonlinear Optics: a nonclassical journey from the optimization of silicon photomultipliers for Quantum Optics to quantum second-harmonic generation
openIn this thesis, we present our experimental and theoretical work on modern and old topics of Nonlinear Quantum Optics. The thesis is structured as follows.
In the first chapter, we provide a general introduction about the basis of this field, in particular about the main concepts and results that will be needed in the following.
In the second and third chapters, we explain our research on the role of silicon photomultipliers in Quantum Optics experiments. After a specific characterization of the sensors, we used them to detect nonclassical states of light. Different strategies for the estimation of experimental quantities are suggested.
In the fourth chapter, we propose our quantum description for the second-harmonic-generation process, based on well-known perturbative methods. After a general introduction on the state of the art, we immediately dive into the problem by explaining the employed methods and showing our analytical results.
Finally, we resume the essence of our achievements and draw our conclusions.openFisica e astrofisicaChesi, GiovanniChesi, Giovann
Advances in Quantum Nonlinear Optics: a nonclassical journey from the optimization of silicon photomultipliers for Quantum Optics to quantum second-harmonic generation
In this thesis, we present our experimental and theoretical work on modern and old topics of Nonlinear Quantum Optics. The thesis is structured as follows.
In the first chapter, we provide a general introduction about the basis of this field, in particular about the main concepts and results that will be needed in the following.
In the second and third chapters, we explain our research on the role of silicon photomultipliers in Quantum Optics experiments. After a specific characterization of the sensors, we used them to detect nonclassical states of light. Different strategies for the estimation of experimental quantities are suggested.
In the fourth chapter, we propose our quantum description for the second-harmonic-generation process, based on well-known perturbative methods. After a general introduction on the state of the art, we immediately dive into the problem by explaining the employed methods and showing our analytical results.
Finally, we resume the essence of our achievements and draw our conclusions
Squeezing-enhanced phase-shift-keyed binary communication in noisy channels
We address binary phase-shift-keyed communication channels based on Gaussian
states and prove that squeezing improves state discrimination at fixed energy
of the channel, also in the presence of phase diffusion. We then assess
performances of homodyne detection against the ultimate quantum limits to
discrimination, and show that homodyning achieves optimality in large noise
regime. Finally, we consider noise in the preparation of the seed signal
(before phase encoding) and show that also in this case squeezing may improve
state discrimination in realistic conditions.Comment: 6 pages, 5 figure
Tight bounds from multiple-observable entropic uncertainty relations
We investigate the additivity properties for both bipartite and multipartite
systems by using entropic uncertainty relations (EUR) defined in terms of the
joint Shannon entropy of probabilities of local measurement outcomes. In
particular, we introduce state-independent and state-dependent entropic
inequalities. Interestingly, the violation of these inequalities is strictly
connected with the presence of quantum correlations. We show that the
additivity of EUR holds only for EUR that involve two observables, while this
is not the case for inequalities that consider more than two observables or the
addition of the von Neumann entropy of a subsystem. We apply them to bipartite
systems and to several classes of states of a three-qubit system.Comment: 10 pages, 5 figure
A protocol for global multiphase estimation
Global estimation strategies allow to extract information on a phase or a set
of phases without any prior knowledge, which is, instead, required for local
estimation strategies. We devise a global multiphase protocol based on Holevo's
estimation theory and apply it to the case of digital estimation, i.e. we
estimate the phases in terms of the mutual information between them and the
corresponding estimators. In the single-phase scenario, the protocol
encompasses two specific known optimal strategies. We extend them to the
simultaneous estimation of two phases and evaluate their performance. Then, we
retrieve the ultimate digital bound on precision when a generic number of
phases is simultaneously estimated. We show that in the multiphase strategy
there is only a constant quantum advantage with respect to a sequence of
independent single-phase estimations. This extends a recent similar result,
which settled a controversy on the search for the multiphase enhancement
Microbiota-driven interleukin-17-producing cells and eosinophils synergize to accelerate multiple myeloma progression
The gut microbiota has been causally linked to cancer, yet how intestinal microbes influence progression of extramucosal tumors is poorly understood. Here we provide evidence implying that Prevotella heparinolytica promotes the differentiation of Th17 cells colonizing the gut and migrating to the bone marrow (BM) of transgenic Vk*MYC mice, where they favor progression of multiple myeloma (MM). Lack of IL-17 in Vk*MYC mice, or disturbance of their microbiome delayed MM appearance. Similarly, in smoldering MM patients, higher levels of BM IL-17 predicted faster disease progression. IL-17 induced STAT3 phosphorylation in murine plasma cells, and activated eosinophils. Treatment of Vk*MYC mice with antibodies blocking IL-17, IL-17RA, and IL-5 reduced BM accumulation of Th17 cells and eosinophils and delayed disease progression. Thus, in Vk*MYC mice, commensal bacteria appear to unleash a paracrine signaling network between adaptive and innate immunity that accelerates progression to MM, and can be targeted by already available therapies
Strangeness enhancement at mid-rapidity in Pb-Pb collisions at 158 GeV/c
, , , and negative particle yields and transverse mass spectra have been measured at central rapidity in Pb-Pb and p-Pb collisions at 158 GeV/. The yields in Pb-Pb interactions % are presented as a function of the collision centrality and compared with those obtained from p-Pb collisions. Strangeness enhancement in Pb-Pb relative to p-Pb collisions increases with the strangeness content of the particle. Going from p-Pb to Pb-Pb, the strange particle yields increase faster than linearly with the number of participants up to , thereafter the increase becomes %linear with . Yields are studied as a function of the number of nucleons participating in the collision , which is estimated with the Glauber model. From p-Pb to Pb-Pb collisions the particle yields per participant increase substantially. The enhancement is more pronounced for multistrange particles, and exceeds an order of magnitude for the . For a number of participants, , greater than , however, all yields per participant appear to be constant
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