The Nature of the Controversy over Time-Symmetric Quantum Counterfactuals
arXiv:1401.5790
Abstract
It is proposed that the recent controversy over "time-symmetric quantum counterfactuals" (TSQCs), based on the Aharonov-Bergmann-Lebowitz Rule for measurements of pre- and post-selected systems, can be clarified by taking TSQCs to be counterfactuals with a specific type of compound antecedent. In that case, inconsistency proofs such as that of Sharp and Shanks (1993) are not applicable, and the main issue becomes not whether such statements are true, but whether they are nontrivial. The latter question is addressed and answered in the negative. Thus it is concluded that TSQCs, understood as counterfactuals with a compound antecedent, are true but only trivially so, and provide no new contingent information about specific quantum systems (except in special cases already identified in the literature).
2003 paper relevant to recent claims concerning pre- and post-selected systems that appear to be based on a generally invalid counterfactual usage of the ABL Rule. The rule does not in general apply to measurements not actually made on a given system between pre- and post-selection. Thus the rule cannot be used to support claims such as a given system having mutually exclusive properties A and B