Placing bounds on Quantum Decoherence in electron diffraction

Caldeira and Leggett’s theory of quantum dissipation predicts a link between decoherence and energy loss for a particle propagating through a Brownian environment, a relationship that is central to understanding the transition between the quantum and classical regimes. Building on this framework, Anglin and Zurek proposed that a resistive metallic surface could act as such a dissipative environment for an aloof free electron wave propagating in close proximity. Some theoretical models predict energy losses exceeding 0.3 eV in this system.

Here, we report measurements of the electron energy with an accuracy better than 0.1 eV, thereby placing stringent constraints on these models. We compare our methods and results with earlier studies by Hasselbach and Stibor (electron interferometry) and Beierle (electron diffraction), and we discuss the implications of W. C. Huang’s modeling approach based on a bouncing electron, in contrast to the aloof-electron picture. As an outlook, experimental tests combining simultaneous measurements of energy loss and interference-contrast loss now appear within reach.