Superposition in quantum states of large systems plays a crucial role in quantum theory and has important fundamental as well as technological implications, ranging from quantum measurement theory to quantum computers. The power of the potential implications of such states lies in the quantum coherence, as measured by the amount of entanglement and other quantum correlations, between its microscopic and macroscopic sectors. We show that in contrast to other macroscopic superposition states, it is possible to choose the states of the macroscopic sector in a way that the resulting state, which we term as the $H_C$ state, has quantum coherence that is resistant to the twin effects of environmental noise: (a) local decoherence on all the particles and (b) loss of a finite fraction of its particles. The states of the macroscopic sector of the $H_C$ state are macroscopically distinct in terms of their violation of Bell inequality.

• Received 7 August 2012

DOI:https://doi.org/10.1103/PhysRevA.87.052117