Quantum Darwinism in quantum Brownian motion: the vacuum as a witness

Understand

We study quantum Darwinism -- the redundant recording of information about a decohering system by its environment -- in zero-temperature quantum Brownian motion.

• An initially nonlocal quantum state leaves a record whose redundancy increases rapidly with its spatial extent.
• Significant delocalization (e.g., a Schroedinger's Cat state) causes high redundancy: many observers can measure the system's position without perturbing it.
• This explains the objective (i.e.