Quantum signatures in a macroscopic dipole moment

Demonstrating signatures of quantum mechanics in macroscopic objects has been a long-standing hurdle since the Schrödinger's cat thought experiment. Here, a novel way to observe the quantum-mechanical behaviour of a macroscopic dipole moment in a large array of quantum wells is proposed. Taking advantage of the cooperative nature of the interaction between the field reservoir and the delocalized exciton in the quantum wells, the exciton dynamics, instead of being purely enhanced decay (superradiance), can reveal Rabi-like oscillations when the number of quantum wells exceeds several hundred. We further show that the oscillations of this "macroscopic" dipole moment in the multiple-quantum-well exhibit "signatures of quantumness" by using an extension of the Leggett-Garg inequality.