Experimental analysis of the quantum complementarity principle

TL;DR

This paper experimentally investigates Bohr's quantum complementarity principle using a molecular quantum information processor and NMR techniques, demonstrating the simultaneous measurement of wave and particle aspects within a superposed interferometer.

Contribution

It introduces a novel experimental setup employing a quantum superposition of open and closed interferometer configurations to measure both quantum aspects simultaneously.

Findings

Confirmed the quantum superposition of interferometer states

Measured both wave and particle behaviors with a single apparatus

Validated the quantum complementarity principle experimentally

Abstract

One of the milestones of quantum mechanics is Bohr's complementarity principle. It states that a single quantum can exhibit a particle-like \emph{or} a wave-like behaviour, but never both at the same time. These are mutually exclusive and complementary aspects of the quantum system. This means that we need distinct experimental arrangements in order to measure the particle or the wave nature of a physical system. One of the most known representations of this principle is the single-photon Mach-Zehnder interferometer. When the interferometer is closed an interference pattern is observed (wave aspect of the quantum) while if it is open, the quantum behaves like a particle. Here, using a molecular quantum information processor and employing nuclear magnetic resonant (NMR) techniques, we analyze the quantum version of this principle by means of an interferometer that is in a quantum superposition of being closed and open, and confirm that we can indeed measure both aspects of the system with the same experimental apparatus. More specifically, we observe with a single apparatus the interference between the particle and the wave aspects of a quantum system.