Kvantno sprezanje

Kvantno sprezanje je fizički fenomen koji se pojavljuje kada parovi ili grupe čestica nastanu ili međudeluju na takav način da se kvantno stanje pojedinačnih čestica ne može utvrditi nezavisno od drugih čestica, čak i ako čestice u pitanju dele velike udaljenosti. Umesto toga, mora se uzeti kvantno stanje sistema kao celine.

Merenja fizičkih svojstava, poput položaja, momenta, spina, ili polarizacije, na spregnutim česticama blisko su povezana. Na primer, ako je paru spregnutih čestica ukupni spin nula, a za jednu česticu se zna kako ima spin u smeru kazaljke na satu na nekoj osi, spin druge čestice, meren po istoj osi, uvek će biti obrnutog smera, kao što se može i očekivati. Međutim, takvo ponašanje može dovesti do paradoksalnih učinaka: bilo kakvo merenje svojstva čestice može se gledati kao uticanje na tu česticu (npr. kolapsom broja superpozicijskih stanja), što će promeniti originalno kvantno svojstvo; a u slučaju spregnutih čestica, takvo se merenje može izvesti samo na sistemu kao celini. Tada izgleda kao da jedna čestica spregnutog sistema „zna” koja su merenja izvedena na drugoj čestici, i s kojim rezultatima, iako nema poznatog načina izmene takvih informacija između čestica, koje mogu biti na bilo kojoj međusobnoj udaljenosti.

Takvi fenomeni bili su tema naučnog rada koji su 1935. napisali Albert Ajnštajn, Boris Podolski, i Nejtan Rozen,^[1] kao i nekoliko radova Ervina Šredingera nešto kasnije,^[2]^[3] koji opisuju, kasnije nazvani, EPR paradoks. Ajnštajn i drugi smatrali su takvo ponašanje nemogućim, jer je kršilo teoriju relativnosti (Ajnštajn je to nazvao „sablasno delovanje na daljinu”)^[4] te je tvrdio kako je zbog toga tadašnja interpretacija kvantne mehanike nepotpuna. Kasnije su kontraintuitivna predviđanja kvantne mehanike potvđena.^[5] Izvedeni su eksperimenti koji uključuju merenje polarizacije ili spina spregnutih čestica u drugim smerovima, koji su – kršeći Belovu nejednakost – statistički demonstrirali kako je Kopenhagenska interpretacija ispravna. To se događa čak i kad su merenja izvedena na dva mesta brže nego što svetlo može stići od jedne laboratorije do druge, što dokazuje kako čestice među sobom ne razmenjuju informacije.^[6] Prema formalizaciji kvantne teorije, efekti merenja su trenutni.^[7]^[8] Nije moguće koristiti ovaj učinak za prenošenje informacija brzinom većom od svetlosne.^[9]

Kvantno sprezanje je područje veoma aktivnih istraživanja, čiji su učinci eksperimentalno demonstrirani na fotonima,^[10]^[11]^[12]^[13] neutrinima,^[14] elektronima,^[15]^[16] molekulima veličine fulerena,^[17]^[18] čak i malih dijamanata.^[19]^[20] Istraživanja se takođe fokusiraju na iskorištavanje navedenih učinaka za svrhe komunikacije i kvantnih računara.

Reference[уреди | уреди извор]

^ Einstein A, Podolsky B, Rosen N; Podolsky; Rosen (1935). „Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?”. Phys. Rev. 47 (10): 777—780. Bibcode:1935PhRv...47..777E. doi:10.1103/PhysRev.47.777.
^ Schrödinger E (1935). „Discussion of probability relations between separated systems”. Mathematical Proceedings of the Cambridge Philosophical Society. 31 (4): 555—563. Bibcode:1935PCPS...31..555S. doi:10.1017/S0305004100013554.
^ Schrödinger E (1936). „Probability relations between separated systems”. Mathematical Proceedings of the Cambridge Philosophical Society. 32 (3): 446—452. Bibcode:1936PCPS...32..446S. doi:10.1017/S0305004100019137.
^ Physicist John Bell depicts the Einstein camp in this debate in his article entitled "Bertlmann's socks and the nature of reality", p. 143 of Speakable and unspeakable in quantum mechanics: "For EPR that would be an unthinkable 'spooky action at a distance'. To avoid such action at a distance they have to attribute, to the space-time regions in question, real properties in advance of observation, correlated properties, which predetermine the outcomes of these particular observations. Since these real properties, fixed in advance of observation, are not contained in quantum formalism, that formalism for EPR is incomplete. It may be correct, as far as it goes, but the usual quantum formalism cannot be the whole story." And again on p. 144 Bell says: "Einstein had no difficulty accepting that affairs in different places could be correlated. What he could not accept was that an intervention at one place could influence, immediately, affairs at the other." Downloaded 5 July 2011 from Bell, J. S. (1987). Speakable and Unspeakable in Quantum Mechanics (PDF). CERN. ISBN 978-0-521-33495-2. Архивирано из оригинала (PDF) 12. 04. 2015. г. Приступљено 14. 6. 2014.
^ „75 years of entanglement – Science News”. Архивирано из оригинала 26. 10. 2012. г. Приступљено 13. 10. 2014.
^ Francis, Matthew. Quantum entanglement shows that reality can't be local, Ars Technica, 30. 10. 2012.
^ Matson, John (13. 8. 2012). „Quantum teleportation achieved over record distances”. Nature.
^ Griffiths, David J. (2004), Introduction to Quantum Mechanics (2nd ed.), Prentice Hall, ISBN 978-0-13-111892-8
^ Roger Penrose, The Road to Reality: A Complete Guide to the Laws of the Universe, London, 2004, p. 603.
^ „New High-Intensity Source of Polarization-Entangled Photon Pairs”. Physical Review Letters. 75: 4337—4341. Bibcode:1995PhRvL..75.4337K. doi:10.1103/PhysRevLett.75.4337.
^ „Experimental demonstration of five-photon entanglement and open-destination teleportation”. Nature. 430: 54—58. 2004. Bibcode:2004Natur.430...54Z. PMID 15229594. arXiv:quant-ph/0402096 . doi:10.1038/nature02643.
^ „Experimental entanglement of six photons in graph states”. Nature Physics. 3: 91—95. Bibcode:2007NatPh...3...91L. arXiv:quant-ph/0609130 . doi:10.1038/nphys507.
^ „Observation of eight-photon entanglement”. Nature Photonics. 6: 225—228. Bibcode:2012NaPho...6..225Y. arXiv:1105.6318 . doi:10.1038/nphoton.2011.354.
^ J. A. Formaggio, D. I. Kaiser, M. M. Murskyj, and T. E. Weiss (2016), "Violation of the Leggett-Garg inequality in neutrino oscillations". Phys. Rev. Lett. Prihvaćeno 23. lipnja 2016. https://journals.aps.org/prl/accepted/6f072Y00C3318d41f5739ec7f83a9acf1ad67b002
^ Hensen, B.; et al. (21. 10. 2015). „Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres”. Nature. 526: 682—686. Bibcode:2015Natur.526..682H. doi:10.1038/nature15759. Приступљено 21. 10. 2015. Vidi i free online access version.
^ Markoff, Jack (21. 10. 2015). „Sorry, Einstein. Quantum Study Suggests 'Spooky Action' Is Real.”. New York Times. Приступљено 21. 10. 2015.
^ „Wave–particle duality of C₆₀ molecules”. Nature. 401: 680—682. 14. 10. 1999. Bibcode:1999Natur.401..680A. PMID 18494170. doi:10.1038/44348. (потребна претплата)
^ Olaf Nairz, Markus Arndt, and Anton Zeilinger, "Quantum interference experiments with large molecules", American Journal of Physics, 71 (April 2003) 319–325.
^ Lee, K. C.; Sprague, M. R.; Sussman, B. J.; Nunn, J.; Langford, N. K.; Jin, X.- M.; Champion, T.; Michelberger, P.; Reim, K. F.; England, D.; Jaksch, D.; Walmsley, I. A. (2. 12. 2011). „Entangling macroscopic diamonds at room temperature”. Science. 334 (6060): 1253—1256. Bibcode:2011Sci...334.1253L. PMID 22144620. doi:10.1126/science.1211914. Генерални сажетак.
^ sciencemag.org, supplementary materials

Reference[уреди | уреди извор]

Bengtsson, I.; K, Życzkowski (2006). „Geometry of Quantum States”. An Introduction to Quantum Entanglement. Cambridge: Cambridge University Press. second, revised edition (2017)
Cramer, JG (2015). The Quantum Handshake: Entanglement, Nonlocality and Transactions. Springer Verlag. ISBN 978-3-319-24642-0.
Gühne, O.; Tóth, G. (2009). „Entanglement detection”. Physics Reports. 474 (1–6): 1—75. Bibcode:2009PhR...474....1G. arXiv:0811.2803 . doi:10.1016/j.physrep.2009.02.004.
Horodecki R, Horodecki P, Horodecki M, Horodecki K; Horodecki; Horodecki; Horodecki (2009). „Quantum entanglement”. Rev. Mod. Phys. 81 (2): 865—942. Bibcode:2009RvMP...81..865H. arXiv:quant-ph/0702225 . doi:10.1103/RevModPhys.81.865.
Jaeger, G. (2009). Entanglement, Information, and the Interpretation of Quantum Mechanics. Heildelberg: Springer. ISBN 978-3-540-92127-1.
Plenio MB, Virmani S; Virmani (2007). „An introduction to entanglement measures”. Quant. Inf. Comp. 1 (7): 1—51. Bibcode:2005quant.ph..4163P. arXiv:quant-ph/0504163 .
Shadbolt PJ, Verde MR, Peruzzo A, Politi A, Laing A, Lobino M, Matthews JCF, Thompson MG, O'Brien JL; Verde; Peruzzo; Politi; Laing; Lobino; Matthews; Thompson; O'Brien (2012). „Generating, manipulating and measuring entanglement and mixture with a reconfigurable photonic circuit”. Nature Photonics. 6 (1): 45—59. Bibcode:2012NaPho...6...45S. arXiv:1108.3309 . doi:10.1038/nphoton.2011.283.
Steward, E. G. (2008). Quantum Mechanics: Its Early Development and the Road to Entanglement. Imperial College Press. ISBN 978-1-86094-978-4.
Vedral, V. (2002). „The role of relative entropy in quantum information theory”. Reviews of Modern Physics. 74 (1): 197—234. Bibcode:2002RvMP...74..197V. arXiv:quant-ph/0102094 . doi:10.1103/RevModPhys.74.197.

Spoljašnje veze[уреди | уреди извор]

[Einstein1935-1] Einstein A, Podolsky B, Rosen N; Podolsky; Rosen (1935). „Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?”. Phys. Rev. 47 (10): 777—780. Bibcode:1935PhRv...47..777E. doi:10.1103/PhysRev.47.777.

[Schrödinger1935-2] Schrödinger E (1935). „Discussion of probability relations between separated systems”. Mathematical Proceedings of the Cambridge Philosophical Society. 31 (4): 555—563. Bibcode:1935PCPS...31..555S. doi:10.1017/S0305004100013554.

[Schrödinger1936-3] Schrödinger E (1936). „Probability relations between separated systems”. Mathematical Proceedings of the Cambridge Philosophical Society. 32 (3): 446—452. Bibcode:1936PCPS...32..446S. doi:10.1017/S0305004100019137.

[4] Physicist John Bell depicts the Einstein camp in this debate in his article entitled "Bertlmann's socks and the nature of reality", p. 143 of Speakable and unspeakable in quantum mechanics: "For EPR that would be an unthinkable 'spooky action at a distance'. To avoid such action at a distance they have to attribute, to the space-time regions in question, real properties in advance of observation, correlated properties, which predetermine the outcomes of these particular observations. Since these real properties, fixed in advance of observation, are not contained in quantum formalism, that formalism for EPR is incomplete. It may be correct, as far as it goes, but the usual quantum formalism cannot be the whole story." And again on p. 144 Bell says: "Einstein had no difficulty accepting that affairs in different places could be correlated. What he could not accept was that an intervention at one place could influence, immediately, affairs at the other." Downloaded 5 July 2011 from Bell, J. S. (1987). Speakable and Unspeakable in Quantum Mechanics (PDF). CERN. ISBN 978-0-521-33495-2. Архивирано из оригинала (PDF) 12. 04. 2015. г. Приступљено 14. 6. 2014.

[5] „75 years of entanglement – Science News”. Архивирано из оригинала 26. 10. 2012. г. Приступљено 13. 10. 2014.

[6] Francis, Matthew. Quantum entanglement shows that reality can't be local, Ars Technica, 30. 10. 2012.

[7] Matson, John (13. 8. 2012). „Quantum teleportation achieved over record distances”. Nature.

[Griffiths2004-8] Griffiths, David J. (2004), Introduction to Quantum Mechanics (2nd ed.), Prentice Hall, ISBN 978-0-13-111892-8

[9] Roger Penrose, The Road to Reality: A Complete Guide to the Laws of the Universe, London, 2004, p. 603.

[10] „New High-Intensity Source of Polarization-Entangled Photon Pairs”. Physical Review Letters. 75: 4337—4341. Bibcode:1995PhRvL..75.4337K. doi:10.1103/PhysRevLett.75.4337.

[11] „Experimental demonstration of five-photon entanglement and open-destination teleportation”. Nature. 430: 54—58. 2004. Bibcode:2004Natur.430...54Z. PMID 15229594. arXiv:quant-ph/0402096 . doi:10.1038/nature02643.

[12] „Experimental entanglement of six photons in graph states”. Nature Physics. 3: 91—95. Bibcode:2007NatPh...3...91L. arXiv:quant-ph/0609130 . doi:10.1038/nphys507.

[13] „Observation of eight-photon entanglement”. Nature Photonics. 6: 225—228. Bibcode:2012NaPho...6..225Y. arXiv:1105.6318 . doi:10.1038/nphoton.2011.354.

[14] J. A. Formaggio, D. I. Kaiser, M. M. Murskyj, and T. E. Weiss (2016), "Violation of the Leggett-Garg inequality in neutrino oscillations". Phys. Rev. Lett. Prihvaćeno 23. lipnja 2016. https://journals.aps.org/prl/accepted/6f072Y00C3318d41f5739ec7f83a9acf1ad67b002

[NTR-20151021-15] Hensen, B.; et al. (21. 10. 2015). „Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres”. Nature. 526: 682—686. Bibcode:2015Natur.526..682H. doi:10.1038/nature15759. Приступљено 21. 10. 2015. Vidi i free online access version.

[NYT-20151021-16] Markoff, Jack (21. 10. 2015). „Sorry, Einstein. Quantum Study Suggests 'Spooky Action' Is Real.”. New York Times. Приступљено 21. 10. 2015.

[17] „Wave–particle duality of C₆₀ molecules”. Nature. 401: 680—682. 14. 10. 1999. Bibcode:1999Natur.401..680A. PMID 18494170. doi:10.1038/44348. (потребна претплата)

[18] Olaf Nairz, Markus Arndt, and Anton Zeilinger, "Quantum interference experiments with large molecules", American Journal of Physics, 71 (April 2003) 319–325.

[19] Lee, K. C.; Sprague, M. R.; Sussman, B. J.; Nunn, J.; Langford, N. K.; Jin, X.- M.; Champion, T.; Michelberger, P.; Reim, K. F.; England, D.; Jaksch, D.; Walmsley, I. A. (2. 12. 2011). „Entangling macroscopic diamonds at room temperature”. Science. 334 (6060): 1253—1256. Bibcode:2011Sci...334.1253L. PMID 22144620. doi:10.1126/science.1211914. Генерални сажетак.

[20] sciencemag.org, supplementary materials

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