Simulating all Nonsignaling Correlations via Classical or Quantum Theory with Negative Probabilities

Many-party correlations between measurement outcomes in general probabilistic theories are given by conditional probability distributions obeying the nonsignaling condition. We show that any such distribution can be obtained from classical or quantum theory by relaxing positivity constraints on either the mixed state shared by the parties or the local functions that generate measurement outcomes. Our results apply to generic nonsignaling correlations, but in particular they yield two distinct quasiclassical models for quantum correlations.