Einstein-Bohr recoiling double-slit gedanken experiment performed at the molecular level - complementarity unveiled by decoupling coupled slits

by Faris Gelmukhanov (KTH Theoretical Chemistry & Biology)

Tuesday 10 Nov 2015, 13:30 → 14:30 Europe/Stockholm

122:026

Double-slit experiments illustrate the quintessential proof for wave–particle complementarity [1]. If information is missing about which slit the particle has traversed, the particle, behaving as a wave, passes simultaneously through both slits. This wave-like behaviour and corresponding interference is absent if ‘which-slit’ information exists. The essence of Einstein– Bohr’s debate [1] about wave–particle duality was whether the momentum transfer between a particle and a recoiling slit could mark the path, thus destroying the interference. However, when using macroscopic slits, momentum transfer from the particle to the slit is too small to be measured. Due to this we use ultra-light atomic slits. To measure the recoil of a slit, the slits should move independently. We showcase a materialization of this recoiling double-slit gedanken experiment by resonant X-ray photoemission from molecular oxygen for geometries near equilibrium (coupled slits) and in a dissociative state far away from equilibrium (decoupled slits) [2]. Interference is observed in the former case, while the electron momentum transfer quenches the interference in the latter case owing to Doppler labelling of the counter-propagating atomic slits, in full agreement with Bohr’s complementarity.  

References
1. Quantum Theory and Measurement (eds Wheeler, J. A. & Zurek, W. H.) 9–49 (Princeton Univ. Press, 1983).
2. X-J. Liu, Q. Miao, F.Gel’mukhanov, M. Patanen, O.Travnikova, C. Nicolas, H. Ågren, K. Ueda and C. Miron. Nature Photonics 9, 120-125 (2015).