| 1. |
- Aerts, Sven, et al.
(författare)
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Two-photon Franson-type experiments and local realism
- 1999
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 83:15, s. 2872-2876
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Tidskriftsartikel (refereegranskat)abstract
- The two-photon interferometric experiment proposed by J. D. Franson [Phys. Rev. Lett. 62, 2205 (1989)] is often treated as a “Bell test of local realism.” However, it has been suggested that this is incorrect due to the 50% postselection performed even in the ideal gedanken version of the experiment. Here we present a simple local hidden variable model of the experiment that successfully explains the results obtained in usual realizations of the experiment, even with perfect detectors. Furthermore, we also show that there is no such model if the switching of the local phase settings is done at a rate determined by the internal geometry of the interferometers.
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| 2. |
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| 4. |
- Larsson, Jan-Åke, 1969-
(författare)
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Bell’s inequality and detector inefficiency
- 1998
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 57:5, s. 3304-3308
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a method of generalizing the Bell inequality is presented that makes it possible to include detector inefficiency directly in the original Bell inequality. To enable this, the concept of “change of ensemble” will be presented, providing both qualitative and quantitative information on the nature of the “loophole” in the proof of the original Bell inequality. In a local hidden-variable model lacking change of ensemble, the generalized inequality reduces to an inequality that quantum mechanics violates as strongly as the original Bell inequality, irrespective of the level of efficiency of the detectors. A model that contains change of ensemble lowers the violation, and a bound for the level of change is obtained. The derivation of the bound in this paper is not dependent upon any symmetry assumptions such as constant efficiency, or even the assumption of independent errors.
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| 5. |
- Larsson, Jan-Åke, 1969-
(författare)
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Detector efficiency in the Greenberger-Horne-Zeilinger paradox : independent errors
- 1999
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 59:6, s. 4801-4804
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Tidskriftsartikel (refereegranskat)abstract
- The Greenberger-Horne-Zeilinger (GHZ) paradox is subject to the detector-efficiency “loophole” in a similar manner as the Bell inequality. In a paper by J.-Å. Larsson [Phys. Rev. A 57, R3145 (1998)], the issue is investigated for very general assumptions. Here, the assumptions of constant efficiency and independent errors will be imposed, and it will be shown that the necessary and sufficient efficiency bound is not lowered, but remains at 75%. An explicit local-variable model is constructed in this paper to show the necessity of this bound. In other words, it is not possible to use the independence of experimental nondetection errors to rule out local realism in the GHZ paradox below 75% efficiency.
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| 6. |
- Larsson, Jan-Åke, 1969-
(författare)
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Modeling the singlet state with local variables
- 1999
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Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 256:4, s. 245-252
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Tidskriftsartikel (refereegranskat)abstract
- A local-variable model yielding the statistics from the singlet state is presented for the case of inefficient detectors and/or lowered visibility. It has independent errors and the highest efficiency at perfect visibility is 77.80%, while the highest visibility at perfect detector-efficiency is 63.66%. The model cannot be refuted by measurements made to date.
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| 7. |
- Larsson, Jan-Åke, 1969-
(författare)
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Necessary and sufficient detector-efficiency conditions for the Greenberger-Horne-Zeilinger paradox
- 1998
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 57:5, s. R3145-R3149
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Tidskriftsartikel (refereegranskat)abstract
- In this paper detector efficiency conditions are derived for the Greenberger-Horne-Zeilinger (GHZ) paradox. The conditions will be necessary and sufficient, i.e., the GHZ paradox is explicable in terms of a local-variable model if the efficiency is below the bounds, and the GHZ prerequisites are inconsistent at higher efficiencies. The derivation does not make use of any of the symmetry assumptions usually made in the literature, most notably the assumption of independent errors. The errors in local-hidden-variable models are governed by the “hidden variable” and, therefore, one cannot in general assume that the errors are independent. It will be shown that this assumption is not necessary. Moreover, bounds are presented that do not need the emission rate of particle triples to be known. An example of such a bound is the ratio of the triple coincidence rate and the double coincidence rate at two detectors, which needs to be higher than 75% to yield a contradiction.
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| 8. |
- Larsson, Åke, et al.
(författare)
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Increased pollution in the protective earth
- 1997
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Ingår i: EPE '97. - : EPE Association. - 9075815026 ; , s. 823-828
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Konferensbidrag (refereegranskat)abstract
- EMC has received increasing interest over past decade. Several standards regarding EMC have been developed. Although manufacturers design and manufacture interference-free equipment in accordance with standards, disturbances are still a problem. According to the current EMC legislation, conducted emissions are to be measured using a LISN between the utility grid and the equipment under test. However, it should be noticed that there is no correspondence between the EMC environment measured at an installation site and the EMC environment measured by the LISN. In this paper some documented cases where electrical equipment are disturbing each other are highlighted and EMC standards are discussed. In the paper it is shown that EMC related problems occurring in the examples all have the same origin: current flow in the PE. The leakage current is fed into the PE via the filters or by a capacitive coupling to the ground. The increased use of power electronic equipment might lead to the need of a complete re-build of the entire grid. An alternative solution to the problem would be to stop the leakage current from being fed into the PE.
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