An undergraduate laboratory study of the polarisation of annihilation photons using Compton scattering

Abstract

An experiment for the advanced undergraduate laboratory which allows students to study the effect of photon polarisation in Compton scattering and to explore quantum entanglement is described. The quantum entangled photons are produced through electron-positron annihilation in the S-state, and their polarisations are analysed using the Compton scattering cross-section dependence on the photon polarisation. The experiment was equipped with off-the-shelf detectors and electronic units. Finite geometry effects are discussed and investigated with the use of a Geant4based simulation.

Setup to study the Compton scattering of entangled annihilation photons

“…The pair of photons is identified as decoherent one if non-zero energy was deposited in additional scatterer within the true coincidence time window. Measured ratio of maximum/minimum numbers of entangled gammas R experiment (θ=90 0 )=2.51±0.05 is close to the theoretical R theory (θ=90 0 )=2.6 [2] [3]. The same ratio for decoherent gammas is R decoherent (θ=90 0 )=2.09±0.15.…”