Local decoherence-resistant quantum states of large systems

• We identify an effectively decoherence-free class of quantum states of large systems.
• We work with local noise models.
• Decay of entanglement as well as information-theoretic quantum correlations considered.
• The states are of the form of the Schrödinger cats, with minuscule and large sectors.
• The states of the large sector are distinguishable by their violation of Bell inequality.

We identify an effectively decoherence-free class of quantum states, each of which consists of a “minuscule” and a “large” sector, against local noise. In particular, the content of entanglement and other quantum correlations in the minuscule to large partition is independent of the number of particles in their large sectors, when all the particles suffer passage through local amplitude and phase damping channels. The states of the large sectors are distinct in terms of markedly different amounts of violation of Bell inequality. In case the large sector is macroscopic, such states are akin to the Schrödinger cat.