Objectivity in a Noisy Photonic Environment through Quantum State Information Broadcasting

Recently, the emergence of classical objectivity as a property of a quantum state has been explicitly derived for a small object embedded in a photonic environment in terms of a spectrum broadcast form—a specific classically correlated state, redundantly encoding information about the preferred states of the object in the environment. However, the environment was in a pure state and the fundamental problem was how generic and robust is the conclusion. Here, we prove that despite the initial environmental noise, the emergence of the broadcast structure still holds, leading to the perceived objectivity of the state of the object. We also show how this leads to a quantum Darwinism-type condition, reflecting the classicality of proliferated information in terms of a limit behavior of the mutual information. Quite surprisingly, we find “singular points” of the decoherence, which can be used to faithfully broadcast a specific classical message through the noisy environment.

Figure 1

The illuminated sphere model [12]. Green dots represent the photons, which constitute the environments $E_1,\dots ,E_N$ of the sphere. The sphere and the photons are enclosed in a large cubic box of edge $L$; photon momentum eigenstates $|\overrightarrow{k}⟩$ obey the periodic boundary conditions.