Person: Luis Aina, Alfredo
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First Name
Alfredo
Last Name
Luis Aina
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Óptica
Area
Optica
Identifiers
15 results
Search Results
Now showing 1 - 10 of 15
Item Probability distributions for the phase difference(Physical review A, 1996) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoIn this work we analyze the quantum phase properties of pairs of electromagnetic field modes. Since phases differing by 2π are physically indistinguishable, we propose a general procedure to obtain the correct mod(2π) probability distributions for the phase difference. This allows us to investigate the properties of a number of phase approaches. This procedure provides deeper insight into the quantum nature of the phase difference. We relate this problem to the representation of nonbijective canonical transformations in quantum mechanics.Item Reply to ‘‘Comment on ‘Phase-difference operator’ ’’(Physical review A, 1995) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoIn response to the objection raised by Pegg and Vaccaro [the preceding Comment] we point out that their example is not a difhculty in directly representing the phase difference by the φ12 operator. In fact, we argue that it is a property common to a wide range of phase descriptions, including the Pegg-Barnett formalism.Item Anti-Zeno effect in parametric down-conversion(Physical review A, 1998) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoTwo examples are presented where the observation of the emission in parametric down-conversion leads to its enhancement instead of its inhibition. The improvement is analyzed in terms of the quantum features of the observation.Item Canonical transformations to action and phase-angle variables and phase operators(Physical review A, 1993) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoThe well-known difficulties of defining a phase operator of an oscillator are considered from the point of view of the canonical transformation to action and phase-angle variables. This transformation turns out to be nonbijective, i.e., it is not a one-to-one onto mapping. In order to make possible the unitarity of its representations in quantum optics we should enlarge the Hilbert space of the problem. In this enlarged space we find a phase operator that, after projection, reproduces previous candidates to represent a well-behaved phase operator in the quantum domain.Item Multimode quantum analysis of an interferometer with moving mirrors(Physical review A, 1992) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoA multimode quantum analysis of noise reduction in interferometric measurements is presented. A unitary transformation relating the output modes with the input ones for a Michelson interferometer with moving mirrors is given. The evaluation of the noise spectrum shows that with a proper choice of the input states, the sensitivity of the interferometer can be pushed beyond the standard quantum limit. The results are compared with a semiclassical analysis.Item Complete characterization of arbitrary quantum measurement processes(Physical review letters, 1999) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoWe examine two simple and feasible practical schemes allowing the complete determination of any quantum measuring arrangement. This is illustrated with the example of parity measurement.Item Dynamics of a two-level atom observed via an interaction-free measurement(Physical review A, 1999) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoWe examine the evolution of a two-level atom when its population is monitored. The detection proposed is an interaction-fret measurement, so that the observation occurs without photon exchange between the atom and the apparatus. It is shown that the observed dynamics exhibits features that an isolated two-level atom cannot accommodate. Such phenomena are explained in terms of an atom-apparatus effective interaction.Item Phase-difference operator(Physical review A, 1993) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoWe introduce a unitary operator representing the exponential of the phase difference between two modes of the electromagnetic field. The eigenvalue spectrum has a discrete character that is fully analyzed. We relate this operator with a suitable polar decomposition of the Stokes parameters of the field, obtaining a natural classical limit. The cases of weakly and highly excited states are considered, discussing to what extent it is possible to talk about the phase for a single-mode field. This operator is applied to some interesting two-mode fields.Item Comment on "Complementarity enforced by random classical phase kicks" Luis and Sanchez-Soto reply(Physical review letters, 2000) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoItem Relative phase for a quantum field interacting with a two-level system(Physical review A, 1997) Luis Aina, Alfredo; Sánchez Soto, Luis LorenzoSeveral quantum descriptions of the relative phase between an atomic dipole and a one-mode electromagnetic field are examined. Positive-operator measures for this variable are derived from dipole and field-phase formalisms. They are analyzed and compared with an operator defined by a polar decomposition. Some examples of time evolution are discussed.