A Puzzling Experiment

Sushil K. Sharma, Divya Kumar, Paweł Moskal

The entanglement of photons originating from electron-positron annihilation has not been experimentally proven.owever, the independent experiments performed so far unanimously confirm that the correlation between the linear polarizations of back-to-back photons from electron-positron annihilation is consistent with the assumption that these photons are entangled in the polarization.Yet, unexpectedly, recent experiments differ as regards the correlation of polarization direction of back-to-back photons after the decoherence induced by the scattering of one of these photons on the electron in the scattering material.In one of the experiments, the correlation before and after the decoherence of the photon state is the same, and in the other experiment, the scattering of one photon leads to a significant decrease in this correlation.Here we discuss this puzzle.Decoherent states were ensured provided by forcing one of the annihilation photons to scatter earlier before measuring the polarization correlation based on Compton kinematics.The comparison is made between the experimental setups used for the different measurements, and the results obtained are briefly discussed, highlighting the parameters that are important in performing such measurements.Finally, the main features of the J-PET detector are presented, along with the schemes for performing similar studies, so that the conclusive results can be used as remarks to solve the puzzle in question.Solving the decoherence puzzle will have crucial consequences for basic studies of entanglement, as well as for the proposed application of the photon polarization in positron emission tomography.If the correlation of the polarization of back-to-back photons from the electron-positron annihilation is the same before and after the scattering of these photons, then it will not be useful for the reduction of scatter fraction in positron emission tomography diagnostics.

Costas Christodoulides, George Christodoulides

Itamar Pitowsky

In the mid-nineteenth century George Boole formulated his ‘conditions of possible experience’. These are equations and ineqaulities that the relative frequencies of (logically connected) events must satisfy. Some of Boole's conditions have been rediscovered in more recent years by physicists, including Bell inequalities, Clauser Horne inequalities, and many others. In this paper, the nature of Boole's conditions and their relation to propositional logic is explained, and the puzzle associated with their violation by quantum frequencies is investigated in relation to a variety of approaches to the interpretation of quantum mechanics.

Pieter Kok

Brett Maynard Bevers

A novel puzzle for the notion of probability in the Many-Worlds interpretation of quantum mechanics is presented. The puzzle makes use of a thought experiment that some have claimed would provide empirical support for many-worlds over alternatives. It is argued that, if the predictions of Many-Worlds do indeed differ from other inter-pretations as claimed, then Born’s rule must generally be invalid in Many-Worlds. It is shown that the thought experiment provides a counter example for recent decision-theoretic arguments that purport to establish Born’s rule. Finally, it is shown that the puzzle can be grounded in general considerations regarding the nature of prediction in Many-Worlds. The Many-Worlds interpretation (MW) of quantum mechanics is routinely mentioned alongside various hidden-variable, collapse and modal formulations as a proposed solution to the quantum measurement problem. The MW is unique among these alternatives, how-ever, for the fact that there is serious contention over what predictions the theory makes. Though Hugh Everett III is credited with first proposing a many-worlds interpretation,