Emergence of singularities from decoherence: Quantum catastrophes

We use a master equation to study the dynamics of two coupled macroscopic quantum systems (e.g., a Josephson junction made of two Bose-Einstein condensates or two spin states of an ensemble of trapped ions) subject to a weak continuous measurement. If the coupling between the two systems is suddenly switched on, the resulting dynamics leads to caustics (fold and cusp catastrophes) in the number-difference probability distribution and at the …