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Search Results: 1 - 10 of 189901 matches for " G. Castagnoli "
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First spectral measurement of the Earth's upwelling emission using an uncooled wideband Fourier transform spectrometer
L. Palchetti,C. Belotti,G. Bianchini,F. Castagnoli
Atmospheric Chemistry and Physics Discussions , 2006,
Abstract: The first spectral measurement of Earth's emitted radiation to space in the wideband range from 100 to 1400 cm 1 with 0.5 cm 1 spectral resolution is presented. The measurement was performed from a stratospheric balloon in tropical region using a Fourier transform spectrometer, during a field campaign held in Brazil in June 2005. The instrument, which has uncooled components including the detector module, is a prototype developed as part of the study for the REFIR (Radiation Explorer in the Far InfraRed) space mission. This paper shows the results of the field campaign with particular attention to the measurement capabilities of the prototype. The results are compared with measurements taken by IASI-balloon (Infrared Atmospheric Sounding Interferometer – Balloon version), aboard the same platform, and with forward model estimations. The infrared signature of clouds is observed in the measurements.
Geometric quantum computation with NMR
J. A. Jones,V. Vedral,A. Ekert,G. Castagnoli
Physics , 1999, DOI: 10.1038/35002528
Abstract: The experimental realisation of the basic constituents of quantum information processing devices, namely fault-tolerant quantum logic gates, requires conditional quantum dynamics, in which one subsystem undergoes a coherent evolution that depends on the quantum state of another subsystem. In particular, the subsystem may acquire a conditional phase shift. Here we consider a novel scenario in which this phase is of geometric rather than dynamical origin. As the conditional geometric (Berry) phase depends only on the geometry of the path executed it is resilient to certain types of errors, and offers the potential of an intrinsically fault-tolerant way of performing quantum gates. Nuclear Magnetic Resonance (NMR) has already been used to demonstrate both simple quantum information processing and Berry's phase. Here we report an NMR experiment which implements a conditional Berry phase, and thus a controlled phase shift gate. This constitutes the first elementary geometric quantum computation.
Experimental evidence for bounds on quantum correlations
F. A. Bovino,G. Castagnoli,I. P. Degiovanni,S. Castelletto
Physics , 2003, DOI: 10.1103/PhysRevLett.92.060404
Abstract: We implemented the experiment proposed by Cabello [arXiv:quant-ph/0309172] to test the bounds of quantum correlation. As expected from the theory we found that, for certain choices of local observables, Cirel'son's bound of the Clauser-Horne-Shimony-Holt inequality ($2\sqrt{2}$) is not reached by any quantum states.
Ipotesi progettuale di rigenerazione urbana: il caso di studio dell’ex Caserma Monti già Convento di S. Maria della Ripa nella città di Forlì Hypothesis for an urban requalification project: case study of the former Caserma Monti (Monti barracks) which was already the Convento di S. Maria della Ripa in the town of Forlì
Alessandro Castagnoli
In_Bo : Ricerche e Progetti per il Territorio, la Città e l'Architettura , 2011,
Abstract: Un’ampia area dismessa nel centro della città storica, è stata considerata l’opportunità strategica per valorizzare e rigenerare anche interi brani di tessuto urbano circostante con l’obiettivo di riammagliare gli sfrangiamenti materiali e immateriali nel complesso rapporto fra passato, presente e futuro. Questo caso di studio ha consentito di approfondire un approccio meta progettuale più generale, puntando sulla ricerca di una metodologia appropriata rispetto alla progettazione dello spazio architettonico in quanto tale, con l’obiettivo di sviluppare ragionamenti di compatibilità nell’ambito della vasta tematica del riuso urbano ed edilizio. A large abandoned area in the centre of the historical part of the town was also considered to be a strategic opportunity for assessing and requalifying entire sections of the surrounding urban structure, with the aim of reworking the material and immaterial wear and tear in the complex relationship between past, present and future. The investigation allowed for the in-depth study of a more general approach, focussing on researching an appropriate methodology with regards to designing the architectural space and developing compatibility reasoning in the sphere of the vast issue of urban and building reuse.
Quantum computation and the physical computation level of biological information processing
Giuseppe Castagnoli
Physics , 2009, DOI: 10.1007/s10773-009-0203-y
Abstract: On the basis of introspective analysis, we establish a crucial requirement for the physical computation basis of consciousness: it should allow processing a significant amount of information together at the same time. Classical computation does not satisfy the requirement. At the fundamental physical level, it is a network of two body interactions, each the input-output transformation of a universal Boolean gate. Thus, it cannot process together at the same time more than the three bit input of this gate - many such gates in parallel do not count since the information is not processed together. Quantum computation satisfies the requirement. At the light of our recent explanation of the speed up, quantum measurement of the solution of the problem is analogous to a many body interaction between the parts of a perfect classical machine, whose mechanical constraints represent the problem to be solved. The many body interaction satisfies all the constraints together at the same time, producing the solution in one shot. This shades light on the physical computation level of the theories that place consciousness in quantum measurement and explains how informations coming from disparate sensorial channels come together in the unity of subjective experience. The fact that the fundamental mechanism of consciousness is the same of the quantum speed up, gives quantum consciousness a potentially enormous evolutionary advantage.
An explanation of the quantum speed up
Giuseppe Castagnoli
Physics , 2009,
Abstract: In former work, we showed that a quantum algorithm requires the number of operations (oracle's queries) of a classical algorithm that knows in advance 50% of the information that specifies the solution of the problem. We gave a preliminary theoretical justification of this "50% rule" and checked that the rule holds for a variety of quantum algorithms. Now, we make explicit the information about the solution available to the algorithm throughout the computation. The final projection on the solution becomes acquisition of the knowledge of the solution on the part of the algorithm. Backdating to before running the algorithm a time-symmetric part of this projection, feeds back to the input of the computation 50% of the information acquired by reading the solution.
Quantum problem solving as simultaneous computation
Giuseppe Castagnoli
Physics , 2007,
Abstract: I provide an alternative way of seeing quantum computation. First, I describe an idealized classical problem solving machine that, thanks to a many body interaction, reversibly and nondeterministically produces the solution of the problem under the simultaneous influence of all the problem constraints. This requires a perfectly accurate, rigid, and reversible relation between the coordinates of the machine parts - the machine can be considered the many body generalization of another perfect machine, the bounching ball model of reversible computation. The mathematical description of the machine, as it is, is applicable to quantum problem solving, an extension of the quantum algorithms that comprises the physical representation of the problem-solution interdependence. The perfect relation between the coordinates of the machine parts is transferred to the populations of the reduced density operators of the parts of the computer register. The solution of the problem is reversibly and nondeterministically produced under the simultaneous influence of the state before measurement and the quantum principle. At the light of the present notion of simultaneous computation, the quantum speed up turns out to be "precognition" of the solution, namely the reduction of the initial ignorance of the solution due to backdating, to before running the algorithm, a time-symmetric part of the state vector reduction on the solution; as such, it is bounded by state vector reduction through an entropic inequality. PACS numbers: 03.67.Lx, 01.55.+b, 01.70.+w
The quantum speed up as advanced knowledge of the solution
Giuseppe Castagnoli
Physics , 2008, DOI: 10.1007/s10773-008-9859-y
Abstract: With reference to a search in a database of size N, Grover states: "What is the reason that one would expect that a quantum mechanical scheme could accomplish the search in O(square root of N) steps? It would be insightful to have a simple two line argument for this without having to describe the details of the search algorithm". The answer provided in this work is: "because any quantum algorithm takes the time taken by a classical algorithm that knows in advance 50% of the information that specifies the solution of the problem". This empirical fact, unnoticed so far, holds for both quadratic and exponential speed ups and is theoretically justified in three steps: (i) once the physical representation is extended to the production of the problem on the part of the oracle and to the final measurement of the computer register, quantum computation is reduction on the solution of the problem under a relation representing problem-solution interdependence, (ii) the speed up is explained by a simple consideration of time symmetry, it is the gain of information about the solution due to backdating, to before running the algorithm, a time-symmetric part of the reduction on the solution; this advanced knowledge of the solution reduces the size of the solution space to be explored by the algorithm, (iii) if I is the information acquired by measuring the content of the computer register at the end of the algorithm, the quantum algorithm takes the time taken by a classical algorithm that knows in advance 50% of I, which brings us to the initial statement.
The 50% advanced information rule of the quantum algorithms
Giuseppe Castagnoli
Physics , 2009, DOI: 10.1007/s10773-009-0031-0
Abstract: The oracle chooses a function out of a known set of functions and gives to the player a black box that, given an argument, evaluates the function. The player should find out a certain character of the function through function evaluation. This is the typical problem addressed by the quantum algorithms. In former theoretical work, we showed that a quantum algorithm requires the number of function evaluations of a classical algorithm that knows in advance 50% of the information that specifies the solution of the problem. Here we check that this 50% rule holds for the main quantum algorithms. In the structured problems, a classical algorithm with the advanced information, to identify the missing information should perform one function evaluation. The speed up is exponential since a classical algorithm without advanced information should perform an exponential number of function evaluations. In unstructured database search, a classical algorithm that knows in advance 50% of the n bits of the database location, to identify the n/2 missing bits should perform Order(2 power n/2) function evaluations. The speed up is quadratic since a classical algorithm without advanced information should perform Order(2 power n) function evaluations. The 50% rule identifies the problems solvable with a quantum sped up in an entirely classical way, in fact by comparing two classical algorithms, with and without the advanced information.
Quantum algorithms know in advance 50% of the solution they will find in the future
Giuseppe Castagnoli
Physics , 2009, DOI: 10.1007/s10773-009-0143-6
Abstract: Quantum algorithms require less operations than classical algorithms. The exact reason of this has not been pinpointed until now. Our explanation is that quantum algorithms know in advance 50% of the solution of the problem they will find in the future. In fact they can be represented as the sum of all the possible histories of a respective "advanced information classical algorithm". This algorithm, given the advanced information (50% of the bits encoding the problem solution), performs the operations (oracle's queries) still required to identify the solution. Each history corresponds to a possible way of getting the advanced information and a possible result of computing the missing information. This explanation of the quantum speed up has an immediate practical consequence: the speed up comes from comparing two classical algorithms, with and without advanced information, with no physics involved. This simplification could open the way to a systematic exploration of the possibilities of speed up.
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