Revealing the emergence of classicality in nitrogen-vacancy centers
Thomas Unden, Daniel Louzon, Michael P. Zwolak, Wojciech Zurek, Fedor Jelezko
The origin of classical behavior of quantum systems is a long-standing mystery. Here, we examine a nitrogen vacancy center evolving naturally in the presence of its environment to study the proliferation of information about preferred quantum states via the environment. This redundantly imprinted information accounts for objective behavior, as it is independently accessible by many without perturbing the system of interest. To observe the emergence of redundant information, we implement a novel dynamical decoupling scheme that enables the measurement/control of several nuclear spins (the environment E) interacting with a nitrogen vacancy (the system S). In addition to showing how to create entangled SE states relevant to quantum metrology, we demonstrate that under the decoherence of S, redundant information is imprinted onto E, giving rise to classical objectivity -- a consensus of the nuclear spins about the state of S. This provides the first laboratory verification of the objective classical behavior emerging from the underlying quantum substrate.