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Are expectation values and weak values properties of single quantum systems?

Lev Vaidman Related
Physics 26/10/2017

Two recent experiments are described. In the first experiment a single click of a detector observing a single photon provides an expectation value of its polarization operator. Another experiment demonstrates that a photon described by a weak value affects other systems much more like a photon described by an eigenvalue rather than a photon described by an expectation value. Physical meaning of results of these experiments is discussed.

Determining the quantum expectation value by measuring a single photon. Fabrizio Piacentini, Alessio Avella, Enrico Rebufello, Rudi Lussana, Federica Villa, Alberto Tosi, Marco Gramegna, Giorgio Brida, Eliahu Cohen, Lev Vaidman, Ivo P. Degiovanni, and Marco Genovese. Nature Physics, doi:10.1038/nphys4223, Published online 14 August 2017.
Weak value beyond conditional expectation value of the pointer readings. Lev Vaidman, Alon Ben-Israel, Jan Dziewior, Lukas Knips, Mira Wei├čl, Jasmin Meinecke, Christian Schwemmer, Ran Ber, and Harald Weinfurter. Physical Review A, accepted 30 August 2017.