Quantum interference experiments with large molecules

Abstract

Wave-particle duality is frequently the first topic students encounter in elementary quantum physics. Although this phenomenon has been demonstrated with photons, electrons, neutrons, and atoms, the dual quantum character of the famous double-slit experiment can be best explained with the largest and most classical objects, which are currently the fullerene molecules. The soccer-ball-shaped carbon cages C 60 are large, massive, and appealing objects for which it is clear that they must behave like particles under ordinary circumstances. We present the results of a multislit diffraction experiment with such objects to demonstrate their wave nature. The experiment serves as the basis for a discussion of several quantum concepts such as coherence, randomness, complementarity, and wave-particle duality. In particular, the effect of longitudinal ͑spectral͒ coherence can be demonstrated by a direct comparison of interferograms obtained with a thermal beam and a velocity selected beam in close analogy to the usual two-slit experiments using light.

Real-time single-molecule imaging of quantum interference

“…Several recent experiments contributed to a further sharpening of the discussion by demonstrating the stochastic build-up of interferograms 11,13 , by implementing double-slit diffraction in the time-domain 14,15 , even down to the attosecond level 16 , and by identifying a single molecule as the smallest double-slit for electron interference 17,18 that enables fundamental decoherence studies 19 . The extension of far-field diffraction 20 to large molecules requires a sufficiently intense and coherent beam of slow and neutral molecules, a nanosized diffraction grating and a detector with both a spatial accuracy of a few nanometers and a molecule specific detection efficiency of close to 100 %. Our present experiment solves all these tasks simultaneously, using advanced micro-preparation, nanodiffraction and nanoimaging technologies.…”

Einstein’s Photon Concept Quantified by the Bohr Model of the Photon

“…• the individual photons will arrive at local positions in the detection plane, whereas the classical continuous wave model predicts a uniformly visible interference pattern: that the former (rather than the latter) is actually observed supports the soliton model [20];…”

“…Double slit interference can be understood by the soliton itself (like the C 60 molecules in Zeilinger's experiment [20]) going through one slit or the other, while its evanescent wave extends over both slits. The evanescent wave is like a classical continuous wave in extending throughout all space, and hence the interference minima and maxima will appear at the same positions as predicted by Huygen's theory.…”

¿Requiere la interferencia de la superposición de ondas como principio físico?

“…Esto ocurre, por ejemplo, cuando la fuente es térmica, como en el experimento original de Young realizado con luz solar (Born & Wolf, 1993), en los experimentos con electrones singulares producidos por termo-ionización (Frabboni, et al, 2012;Matteucci, et al, 2013), o en los que se emplean moléculas individuales por sublimación (Nairz, et al, 2003;Juffmann, et al, 2012). En estos experimentos se cumple que = 0 para todo r' D ≠ 0, de manera que la ecuación (1b) conduce a , (3a) y, por lo tanto, la correlación preparada en el plano M según la ecuación (1a) toma la forma .…”

“…En efecto, ella predice con total precisión el movimiento de ondas y partículas en la etapa MD de cualquier interferó-metro de Young. Esta afirmación se ve validada por: (i) la detección de partículas, cuadro por cuadro, en experimentos de interferencia con partículas singulares (Nairz, et al, 2003;Juffmann, et al, 2009;Matteucci, et al, 2013). Cada cuadro registra, como máximo, un único evento de detección de energía , de manera que el patrón de interferencia se obtiene mediante la adición de dichos cuadros, esto es, , y por (ii) la detección de patrones de interferencia de ondas con distribución de energía en un único cuadro (Born & Wolf, 1993).…”