Knowledge of Past and Future in Quantum Mechanics

Y. Srivastava

Paul Busch, PEKKA J. LAHTI

Albert Einstein, Richard C. Tolman, Boris Podolsky

It is well known that the principles of quantum mechanics limit the possibilities of exact prediction as to the future path of a particle. It has sometimes been supposed, nevertheless, that the quantum mechanics would permit an exact description of the past path of a particle. \n \nThe purpose of the present note is to discuss a simple ideal experiment which shows that the possibility of describing the past pathof one particlewould lead to the predictions as to the future behaviour of a second particle of a kind not allowed in the quantum mechanics. It will hence be concluded that the principles of quantum mechanics actually involve an uncertainty in the description of past events which is analogous to the the uncertainty in the prediction of future events. And it will be shown for the case in hand, that this uncertainty in the description of the past arises from a limitation of the knowledge that can be obtained by measurement of momentum.

Guido Bacciagaluppi, Elise Crull

This is a reprinting of Einstein, Podolsky and Tolman’s 1931 letter to the editor of Physical Review . In this letter, the authors demonstrate that the principles of quantum mechanics give rise to an uncertainty in the description of past events which is analogous to the uncertainty quantum mechanics assigns to the prediction of future events.

Michael Drieschner