The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators
Users of quantum mechanics are familiar with the concept of a statistical mixture as introduced by von Neumann, and with the use of a density operator in that context. A density operator may also be used in another situation, introduced by Landau, with a transient coupling between the two parts of a...
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2025-06-01
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| author | Alain Deville Yannick Deville |
| author_facet | Alain Deville Yannick Deville |
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| description | Users of quantum mechanics are familiar with the concept of a statistical mixture as introduced by von Neumann, and with the use of a density operator in that context. A density operator may also be used in another situation, introduced by Landau, with a transient coupling between the two parts of a quantum bipartite system. But more than fifty years after a clarifying work by Feynman on the subject, a confusion still persists about what we call the Landau-Feynman situation. In this paper we establish that, when facing that situation, the right concept to be used is not the one of a mixed state - be it qualified as proper or improper -, but the one of entanglement. |
| format | Article |
| id | doaj-art-ca5989bfb0ae4b4a8910a264d8675430 |
| institution | Kabale University |
| issn | 2078-2489 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
| record_format | Article |
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| spelling | doaj-art-ca5989bfb0ae4b4a8910a264d86754302025-08-20T03:58:26ZengMDPI AGInformation2078-24892025-06-0116755810.3390/info16070558The Landau-Feynman Transiently Open Quantum System: Entanglement and Density OperatorsAlain Deville0Yannick Deville1Aix-Marseille Université, CNRS, IM2NP UMR 7334, F-13397 Marseille, FranceIRAP (Institut de Recherche en Astrophysique et Planétologie), Université de Toulouse, CNRS, CNES, OMP, F-31400 Toulouse, FranceUsers of quantum mechanics are familiar with the concept of a statistical mixture as introduced by von Neumann, and with the use of a density operator in that context. A density operator may also be used in another situation, introduced by Landau, with a transient coupling between the two parts of a quantum bipartite system. But more than fifty years after a clarifying work by Feynman on the subject, a confusion still persists about what we call the Landau-Feynman situation. In this paper we establish that, when facing that situation, the right concept to be used is not the one of a mixed state - be it qualified as proper or improper -, but the one of entanglement.https://www.mdpi.com/2078-2489/16/7/558quantum state tomographybipartite systemtransient couplingdensity operatorentanglementimproper mixture |
| spellingShingle | Alain Deville Yannick Deville The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators Information quantum state tomography bipartite system transient coupling density operator entanglement improper mixture |
| title | The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators |
| title_full | The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators |
| title_fullStr | The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators |
| title_full_unstemmed | The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators |
| title_short | The Landau-Feynman Transiently Open Quantum System: Entanglement and Density Operators |
| title_sort | landau feynman transiently open quantum system entanglement and density operators |
| topic | quantum state tomography bipartite system transient coupling density operator entanglement improper mixture |
| url | https://www.mdpi.com/2078-2489/16/7/558 |
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