Thinking Inside the Box: Weakly Measuring Postselected Ensembles

          @misc{ pirsa_PIRSA:08090071,
            doi = {10.48660/08090071},
            url = {https://pirsa.org/08090071},
            author = {Steinberg, Aephraim},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Thinking Inside the Box: Weakly Measuring Postselected Ensembles},
            publisher = {Perimeter Institute},
            year = {2008},
            month = {sep},
            note = {PIRSA:08090071 see, \url{https://pirsa.org}}
          }
          

Abstract

The presumed irreversibility of quantum measurements (whatever they are) leads, in conventional approaches to quantum theory, to an asymmetry between state preparation and post-selection. Is it possible that a trajectory can be predicted from the former, yet not inferred from the latter? Especially in light of the exciting applications of non-unitary operations (i.e., postselection) in quantum information, it becomes timely to reconsider how much one can say about a post-selected subensemble. I will review the weak-measurement formalism of Aharonov, Vaidman et al., and discuss some applications and extensions. These will include a proposed experiment to study the duration of the tunneling process (a question controversial since the 1930s) and a recently completed experiment aiming to \'resolve\' Hardy\'s retrodiction paradox.