Uncoupling Which-Way Information from Interference: A Novel Interference Experiment using a Super-Focused Laser Beam

Abstract

The generally accepted view in quantum theory is that information about which way the quantum system traveled and interference visibility are complementary. In all which-way experiments, however, an intervention takes place in the interference process in order to determine which way the quantum system took. This intervention can imply the tagging of a which-way marker to a quantum system or, for instance, blocking off one of the paths in a Mach-Zehnder interferometer so that one indirectly knows that the quantum system took the other (open) path. It is, however, this intervention that destroys the interference. In this paper a novel two-slit which-way interference experiment will be discussed and proposed for implementation that provides maximum which-way information without intervening in the interference process so that simultaneously maximum interference visibility remains preserved. This, in fact, implies an uncoupling of which-way information from interference and consequently also entails violating the duality relation P^2+V^2<1. Basically, the purpose of the proposed experiment and of this paper is to scrutinize this duality relation. The experiment makes use of a super-focused laser beam that is launched into only one of the two slits of the two-slit interference experiment.