A recently proposed stochastic hidden-variable model for quantum mechanics has been claimed to involve “retrocausality” due to the appearance of equations of motion with future-time boundary conditions. We formulate an equivalent system of forward-time equations of motion that gives rise to the same trajectories as solutions, but involves only initial-time boundary conditions. The forward-time dynamics involves a guidance term for the dynamical variables, determined by the phase-space distribution corresponding to a quantum wave function. We show, however, that this particular guidance term can be recovered as the mean-field limit of averaged pairwise interactions among an ensemble of finitely many particles. The results establish a general tradeoff in stochastic models for quantum mechanics between reverse-time and guiding wave formulations.

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• Quantum formalism
• Quantum foundations
• Stochastic processes