On superposition, interference and Feynman paths - Urbasi Sinha

The superposition principle forms the heart of all modern applications and properties of quantum mechanics such as quantum entanglement and quantum computing. However, its usual application to slit based interference experiments has caveat in both optics and quantum mechanics where it is often incorrectly assumed that the boundary condition represented by slits opened individually is same as them being opened together. In theory work carried out over the last few years, we have quantified the correction term in terms of the Sorkin parameter [1, 2]. In this talk, we will report the first reported measurement of a deviation from the superposition principle in the microwave domain using antennas as sources and detectors of the electromagnetic waves. This deviation is quantified through the Sorkin parameter which can be as big as 6% in our experiment [3]. Measuring a non-zero Sorkin parameter not only gives experimental verification to the theoretical predictions about the deviation from the superposition principle in interference experiments, it also exemplifies an experimental scenario in which non zero Sorkin parameter need not necessarily imply falsification of Born rule for probabilities in quantum mechanics which has been the basis for several experiments in recent years [4].
[1] R.Sawant, J.Samuel, A.Sinha, S.Sinha, U.Sinha, Non classical paths in quantum interference experiments. Phys.Rev.Lett.113, 120406 (2014). [2] A.Sinha, Aravind H.V., U.Sinha, On the Superposition principle in interference experiments. Scienti c Reports 5, 10304 (2015). [3] G. Rengaraj, Prathwiraj U, Surya Narayana Sahoo, R. Somashekhar and Urbasi Sinha, Measuring the deviation from the superposition principle in interference experiments, New Journal of Physics 20, 2018. [4] U.Sinha, C.Couteau, T.Jennewein, R.La amme, G.Weihs, Ruling out multi-order interference in quantum mechanics. Science 329, 418-421 (2010).