CQD Special Seminar

15. September 2017 10:00

Konferenzraum 4, 01.106, Physikalisches Institut, INF 226

Can the EPR paradox be resoved without recourse to non-locality?

Keerthan Subramanian
Indian Institute of Science Education and Research (IISER), Pune, India

Can the EPR paradox be resolved without recourse to non-locality?


The completeness debate related to quantum mechanics traces its origin to the seminal paper by Einstein, Podolsky and Rosen (EPR) dating back to 1935. EPR proposed a thought experiment which led one to conclude that either quantum mechanics was incomplete and that a search for local hidden variable theories was justified or that quantum mechanics was complete and that "spooky" action-at-a-distance is an incontrovertible aspect of physical reality. These ideas had to await a simpler formulation by Bohm and a theorem by Bell before this debate could be addressed experimentally. Experimental resolution using entangled photons violating Bell's inequality, some as recent as 2015 closing various loopholes, have only confirmed that quantum mechanics is complete and that our ideas of local realism are untenable with physical reality.

While the spin angular momentum(SAM) associated with photons has been known since almost a century, the revelation that photons can also possess an orbital angular momentum(OAM) is a recent one. This opens up the possibility of creating locally correlated SAM/OAM photon states that are mathematically isomorphic with non-locally correlated entangled states. Measuring the SAM is straightforward as it is related to the polarization, whereas OAM being related to wavefront helicity needs a phase sensitive technique for its projection. We propose and demonstrate an interferometric device that acts as an OAM projector and use it to measure correlations between photon SAM and OAM. We create locally correlated SAM/OAM states and show that strong correlations for such states culminate in a violation of Bell's inequality thereby resolving the EPR debate without taking a recourse to non-locality.


Prof. Dr. M. Weidemüller
Physikalisches Institut
Im Neuenheimer Feld 226
69120 Heidelberg
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