| 1. |
- de la Hoz, P., et al.
(författare)
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Unpolarized states and hidden polarization
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 90:4, s. 043826-
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Tidskriftsartikel (refereegranskat)abstract
- We capitalize on a multipolar expansion of the polarization density matrix, in which multipoles appear as successive moments of the Stokes variables. When all the multipoles up to a given order K vanish, we can properly say that the state is Kth-order unpolarized, as it lacks of polarization information to that order. First-order unpolarized states coincide with the corresponding classical ones, whereas unpolarized to any order tally with the quantum notion of fully invariant states. In between these two extreme cases, there is a rich variety of situations that are explored here. The existence of hidden polarization emerges in a natural way in this context.
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| 2. |
- Zoller, P, et al.
(författare)
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Quantum information processing and communication - Strategic report on current status, visions and goals for research in Europe
- 2005
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 36:2, s. 203-228
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Tidskriftsartikel (refereegranskat)abstract
- We present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission, http://www.cordis.lu/ist/fet/qipc-sr.htm). This document has been elaborated, following a former suggestion by FET, by a committee of QIPC scientists to provide input towards the European Commission for the preparation of the Seventh Framework Program. Besides being a document addressed to policy makers and funding agencies (both at the European and national level), the document contains a detailed scientific assessment of the state-of-the-art, main research goals, challenges, strengths, weaknesses, visions and perspectives of all the most relevant QIPC sub-fields, that we report here.
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| 3. |
- Björk, Gunnar, et al.
(författare)
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Extremal quantum states and their Majorana constellations
- 2015
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 92:3
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Tidskriftsartikel (refereegranskat)abstract
- The characterization of quantum polarization of light requires knowledge of all the moments of the Stokes variables, which are appropriately encoded in the multipole expansion of the density matrix. We look into the cumulative distribution of those multipoles and work out the corresponding extremal pure states. We find that SU(2) coherent states are maximal to any order whereas the converse case of minimal states (which can be seen as the most quantum ones) is investigated for a diverse range of the number of photons. Taking advantage of the Majorana representation, we recast the problem as that of distributing a number of points uniformly over the surface of the Poincare sphere.
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| 4. |
- Bouchard, F., et al.
(författare)
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Quantum metrology at the limit with extremal Majorana constellations
- 2017
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 4:11, s. 1429-1432
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Tidskriftsartikel (refereegranskat)abstract
- Quantum metrology allows for a tremendous boost in the accuracy of measurement of diverse physical parameters. The estimation of a rotation constitutes a remarkable example of this quantum-enhanced precision. The recently introduced Kings of Quantumness are especially germane for this task when the rotation axis is unknown, as they have a sensitivity independent of that axis and they achieve a Heisenberg-limit scaling. Here, we report the experimental realization of these states by generating up to 21-dimensional orbital angular momentum states of single photons, and confirm their high metrological abilities.
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| 5. |
- de la Hoz, P., et al.
(författare)
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Classical polarization multipoles : paraxial versus nonparaxial
- 2015
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 90:7
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the polarization of paraxial and nonparaxial classical light fields by resorting to a multipole expansion of the corresponding polarization matrix. It turns out that only a dipolar term contributes when one considers SU(2) (paraxial) or SU(3) (nonparaxial) as fundamental symmetries. In this latter case, one can alternatively expand in SU(2) multipoles, and then both a dipolar and a quadrupolar component contribute, which explains the richer structure of this nonparaxial instance. These multipoles uniquely determine Wigner functions, in terms of which we examine some intriguing hallmarks arising in this classical scenario.
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| 6. |
- de la Hoz, P., et al.
(författare)
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Multipolar hierarchy of efficient quantum polarization measures
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 88:6, s. 063803-
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Tidskriftsartikel (refereegranskat)abstract
- We advocate a simple multipole expansion of the polarization density matrix. The resulting multipoles appear as successive moments of the Stokes variables and can be obtained from feasible measurements. In terms of these multipoles we construct a whole hierarchy of measures that accurately assess higher-order polarization fluctuations.
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| 7. |
- Klimov, A. B., et al.
(författare)
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Assessing the Polarization of a Quantum Field from Stokes Fluctuations
- 2010
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:15, s. 153602-
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Tidskriftsartikel (refereegranskat)abstract
- We propose an operational degree of polarization in terms of the variance of the Stokes vector minimized over all the directions of the Poincare sphere. We examine the properties of this second-order definition and carry out its experimental determination. Quantum states with the same standard (first-order) degree of polarization are correctly discriminated by this new measure. We argue that a comprehensive quantum characterization of polarization properties requires a whole hierarchy of higher-order degrees.
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| 8. |
- Sánchez-Soto, L. L., et al.
(författare)
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Polarization correlations in quantum optics
- 2011
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Ingår i: Opt.InfoBase Conf. Papers. - 9781557529282
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Konferensbidrag (refereegranskat)abstract
- The standard degree of polarization involves exclusively first-order moments of the Stokes variables. This may be sufficient for most classical problems, but for quantum fields higher-order correlations are crucial. We claim that a complete polarization characterization must involve a whole hierarchy of polarization degrees constructed order by order, as it happens in coherence theory. We present here a second-order degree and determine it experimentally.
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| 9. |
- Söderholm, J., et al.
(författare)
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Quantum polarization characterization and tomography
- 2012
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 115014-
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Tidskriftsartikel (refereegranskat)abstract
- We present a complete polarization characterization of any quantum state of two orthogonal polarization modes and give a systematic measurement procedure to collect the necessary data. Full characterization requires measurements of the photon number in both modes and linear optics. In the case where only the photon-number difference can be determined, a limited but useful characterization is obtained. The characteristic Stokes moment profiles are given for several common quantum states.
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