Weak measurements via quantum erasure - Aharon Brodutch

Quantum mechanical systems with fixed past (pre-selected) and future (post-selected) boundary conditions can exhibit strange properties. In many cases the results of intermediate measurements can give seemingly paradoxical results. It may be argued that such results are counter-factual since the measurement process disturbs the relation between pre and post selection. Weak measurements provide a way to measure observables without disturbing the system thereby allowing us to make factual statements about the apparent paradoxes. For many interesting observables, however, there was no known weak measurement scheme so statements about the result of such measurements cannot be verified experimentally. Examples include non-local observables (such as the Bell observable) and sequential observables (such as those used in Leggett Garg inequalities). Recently we provided a a general scheme for performing weak measurements of a wide range of observables including non-local [1] and sequential [2] observables and illustrated the applicability of this scheme using new paradoxes that demonstrate the strange properties of quantum post-selected systems. In this talk I will begin by reviewing the fundamental significance of weak and non-local measurements and then present the general scheme for performing non-local weak measurements [1]. I will also present a post-selection `paradox' that illustrates the significance of this scheme in both the weak and strong regime. [1] A. Brodutch and E. Cohen, Non-local Weak Measurements via Quantum Erasure, arXiv:1409.1575 (2015). [2] A. Brodutch and E. Cohen Weak and Strong Sequential Measurements, arXiv:1504.07628 (2015).