## On Superposition, Interference and Feynman paths

Raman Research Institute, Bengaluru, India

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. Scientific 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,
arXiv:1610.09143.

[4] U.Sinha, C.Couteau, T.Jennewein, R.Laflamme, G.Weihs, Ruling out multi-order
interference in quantum mechanics. Science 329, 418-421 (2010).