Photodetectors based on polycrystalline diamond (PCD) films are of great interest to many researchers for the attractive electronic, mechanical, optical and thermal properties. PCD films are grown using the Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) method. First, we characterized films by means of structural and morphological analysis (Raman spectroscopy and scanning electron microscopy), then we evaporated a pattern of coplanar interdigitated Cr/Au contacts with an inter-electrode spacing of 100 mu m in order to perform the electrical characterization. We carried out measurements of dark current and impedance spectroscopy to investigate the film properties and conduction mechanisms of films and the effects of post-growth treatments. Finally we developed a charge sensing pre-amplifier to read-out the signal produced by UV photons in the detector. (C) 2009 Elsevier B.V. All rights reserved.

The symmetric states on a quasi local C∗–algebra on the infinite set of indices J are those invariant under the action of the group of the permutations moving only a finite, but arbitrary, number of elements of J . The celebrated De Finetti Theorem describes the structure of the symmetric states (i.e. exchangeable probability measures) in classical probability. In the present paper we extend the De Finetti Theorem to the case of the CAR algebra, that is for physical systems describing Fermions. Namely, after showing that a symmetric state is automatically even under the natural action of the parity automorphism, we prove that the compact convex set of such states is a Choquet simplex, whose extremal (i.e. ergodic w.r.t. the action of the group of permutations previously described) are precisely the product states in the sense of Araki–Moriya. In order to do that, we also prove some ergodic properties naturally enjoyed by the symmetric states which have a self–containing interest.

We analyze general aspects of exchangeable quantum stochastic processes, as well as some concrete cases relevant for several applications to Quantum Physics and Probability. We establish that there is a one-to-one correspondence between quantum stochastic processes, either preserving or not the identity, and states on free product C∗ -algebras, unital or not unital, respectively, where the exchangeable ones correspond precisely to the symmetric states. We also connect some algebraic properties of exchangeable processes, that is the fact that they satisfy the product state or the block-singleton conditions, to some natural ergodic ones. We then specialize the investigation for the q -deformed Commutation Relations, q∈(−1,1) (the case q=0 corresponding to the reduced group C∗ -algebra C∗r(F∞) of the free group F∞ on infinitely many generators), and the Boolean ones. A generalization of de Finetti theorem to the Fermi CAR algebra (corresponding to the q -deformed Commutation Relations with q=−1 ) is proven, by showing that any state is symmetric if and only if it is conditionally independent and identically distributed with respect to the tail algebra. Moreover, we show that the Boolean stochastic processes provide examples for which the condition to be independent and identically distributed w.r.t. the tail algebra, without mentioning the a-priori existence of a preserving conditional expectation, is in general meaningless in the quantum setting. Finally, we study the ergodic properties of a class of remarkable states on the group C∗ -algebra C∗(F∞) , that is the so-called Haagerup states.

We deal with the general structure of the stochastic processes by using the standard techniques of Operator Algebras. In this context, it appears natural that in the quantum case one can exhibit a huge class of such stochastic processes: each of them is associated to a quotient of the universal object made of the free product $C^*$-algebra. The quantum (i.e. noncommutative) case describes the most general situation, and the classical (i.e. commutative) probability scheme is seen as a particular case of the quantum one. The ergodic properties of stationary and exchangeable processes are discussed in detail for many interesting cases arising from Quantum Physics and Quantum Probability.

De Finetti Theorem describes the structure of the symmetric states (i.e. exchangeable probability measures) in classical probability. Here we mainly report two extension of De Finetti Theorem in the case of the CAR algebra. Namely we firstly realize that the compact convex set of such states is a Choquet simplex, whose extremals are precisely the product states in the sense of Araki–Moriya. Then we present a so–called extended version of this result, showing that these states are conditionally independent w.r.t. the tail algebra.

We investigate the spectrum for partial sums of m position (or gaussian) operators on monotone Fock space based on $ell^2(N)$. In the basic case of the rst consecutive operators, we prove it coincides with the support of the vacuum distribution. Thus, the right endpoint of the support gives their norm. In the general case, we get the last property for norm still holds. As the single position operator has the vacuum symmetric Bernoulli law, and the whole of them is a monotone independent family of random variables, the vacuum distribution for partial sums of n operators can be seen as the monotone binomial with n trials. It is a discrete measure supported on a nite set, and we exhibit recurrence formulas to compute its atoms and probability function as well. Moreover, lower and upper bounds for the right endpoints of the supports are given.

We exhibit a Hamel basis for the concrete *-algebra ${\gam_o}$ associated to monotone commutation relations realised on the monotone Fock space, mainly composed by Wick ordered words of annihilators and creators. We apply such a result to investigate spreadability and exchangeability of the stochastic processes arising from such commutation relations. In particular, we show that spreadability comes from a monoidal action implementing a dissipative dynamics on the norm closure C*-algebra $\gam=\overline{\gam_o}$. Moreover, we determine the structure of spreadable and exchangeable monotone stochastic processes using their correspondence with spreading invariant and symmetric monotone states, respectively.