| 1. |
- Badziag, Piotr, et al.
(författare)
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Experimentally friendly geometrical criteria for entanglement
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:14, s. 140403-
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Tidskriftsartikel (refereegranskat)abstract
- A simple geometrical criterion gives experimentally friendly sufficient conditions for entanglement. Its generalization gives a necessary and sufficient condition. It is linked with a family of entanglement identifiers, which is strictly richer than the family of entanglement witnesses.
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| 2. |
- Laskowski, Wieslaw, et al.
(författare)
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Interference contrast in multisource few-photon optics
- 2009
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:11, s. 114004-
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Tidskriftsartikel (refereegranskat)abstract
- Many recent experiments employ several parametric down-conversion (PDC) sources to get multiphoton interference. Such interference has applications in quantum information. We study here how effects due to photon statistics, misalignment and partial distinguishability of the PDC pairs originating from different sources may lower the interference contrast in multiphoton experiments.
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| 3. |
- Rådmark, Magnus, et al.
(författare)
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Experimental filtering of two-, four-, and six-photon singlets from a single parametric down-conversion source
- 2009
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 80:040302
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Tidskriftsartikel (refereegranskat)abstract
- Invariant entangled states remain unchanged under simultaneous identical unitary transformations of all their subsystems. We experimentally generate and characterize such invariant two-, four-, and six-photon polarization entangled states. This is done only with a suitable filtering procedure of multiple emissions of entangled photon pairs from a single source without any interferometric overlaps. We get the desired states utilizing bosonic emission enhancement due to indistinguishability. The setup is very stable and gives high interference contrasts. Thus, the process is a very likely candidate for various photonic demonstrations of quantum information protocols.
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| 4. |
- Rådmark, Magnus, et al.
(författare)
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Experimental high fidelity six-photon entangled state for telecloning protocols
- 2009
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11:103016
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally generate and characterize a six-photon polarizationentangled state, which is usually called ‘9+6 ’. This is realized with a filteringprocedure of triple emissions of entangled photon pairs from a single source,which does not use any interferometric overlaps. The setup is very stable and weobserve the six-photon state with high fidelity. The observed state can be usedfor demonstrations of telecloning and secret sharing protocols.
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| 5. |
- Rådmark, Magnus, et al.
(författare)
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Experimental Test of Fidelity Limits in Six-Photon Interferometry and of Rotational Invariance Properties of the Photonic Six-Qubit Entanglement Singlet State
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:150501
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Tidskriftsartikel (refereegranskat)abstract
- Quantum multiphoton interferometry has now reached the six-photon stage. Thus far, the observed fidelities of entangled states never reached 2/3. We report a high fidelity (estimated at 88%) experiment in which six-qubit singlet correlations were observed. With such a high fidelity we are able to demonstrate the central property of these “singlet” correlations, their “rotational invariance,” by performing a full set of measurements in three complementary polarization bases. The patterns are almost indistinguishable. The data reveal genuine six-photon entanglement. We also study several five-photon states, which result upon detection of one of the photons. Multiphoton singlet states survive some types of depolarization and are thus important in quantum communication schemes.
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| 6. |
- Wiesniak, Marcin, et al.
(författare)
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Explicit form of correlation-function three-setting tight Bell inequalities for three qubits
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:1, s. 12110-
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to derive explicit forms of tight correlation-function Bell inequalities for three systems and dichotomic observables, which involve three settings for each observer. We also give sufficient and necessary conditions for quantum predictions to satisfy the new inequalities.
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| 7. |
- Wu, Yu-Chun, et al.
(författare)
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Clauser-Horne-Shimony-Holt-type Bell inequalities involving a party with two or three local binary settings
- 2009
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 79:2, s. 22110-
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Tidskriftsartikel (refereegranskat)abstract
- We construct a simple algorithm to generate any Clauser-Horne-Shimony-Holt- (CHSH-) type Bell inequality involving a party with two local binary measurements from two CHSH-type inequalities without this party. The algorithm readily generalizes to situations where the additional observer uses three measurement settings. There, each inequality involving the additional party is constructed from three inequalities with this party excluded. With this generalization at hand, we construct and analyze a class of symmetric inequalities for four observers and three experimental settings per observer.
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| 8. |
- Wu, Yu-Chun, et al.
(författare)
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Extending Bell inequalities to more parties
- 2008
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 77:3, s. 32105-
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Tidskriftsartikel (refereegranskat)abstract
- We describe a method of extending Bell inequalities from n to n+ 1 parties and formulate sufficient conditions for our method to produce tight inequalities from tight inequalities. The method is nontrivial in the sense that the inequalities produced by it, when applied to entangled quantum states may be violated stronger than the original inequalities. In other words, the method is capable of generating inequalities which are more powerful indicators of nonclassical correlations than the original inequalities.
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