Visualize the Quantum Behavior of Large Molecules in Real Time
- Build-up of quantum interference. a–e, Selected frames from a false-colour movie recorded with an Andor iXon 885 low-light EMCCD camera showing the build-up of the quantum interference pattern for PcH2 molecules. Images were recorded before deposition of the molecules (a) and 2 min (b), 20 min (c), 40 min (d) and 90 min (e) after deposition. Scale bars, 20 micrometers (a–e). The colour bar ranges from 25 to 120 photons in a–d and from 220 to 650 photons in e. The arrow pointing downwards indicates the direction of the gravitational acceleration g.
The group of Professor Markus Arndt at the University of Vienna, Austria, has shown the diffraction of single, massive molecules at a grating in an unambiguous demonstration of the wave-particle duality of quantum physics.
However, unlike the interference patterns created by photons and electrons that are irretrievably lost in the detection process, Thomas Juffmann et al  used fluorescent molecules and nanometric detection accuracy to provide clear and tangible evidence of the quantum behavior of large molecules in real time.
Statement of Markus Arndt
"The study of duality in large molecules requires a sufficiently intense and coherent beam of slow and neutral molecules, a nanoscale diffraction grating, and a detector that offers a spatial accuracy of a few nanometres and a molecule-specific detection efficiency of close to 100%. We used a laser-controlled micro-evaporation source to produce a beam of phthalocyanine and phthalocyanine-derivative molecules with masses of 514 AMU and 1,298 AMU respectively. The high-mass molecules were specifically synthesized by Jens Tuexen and Prof. Marcel Mayor at the University of Basel. Gratings were machined in 10-nm-thick silicon nitride membranes by the team around Prof. Ori Cheshnovsky at Tel Aviv University. Wide-field microscopy then detected the position of each molecule with an accuracy of 10 nm."
"Vitally, the high detection efficiency of the Andor iXon 885 EMCCD camera allowed us, for the first time, to optically visualize the real-time build-up of a two-dimensional quantum interference pattern caused by individual molecules arriving at the detector. In addition to providing this particularly clear demonstration of wave-particle duality, our approach could also be used to study larger natural and functionalized organic molecules, and also quantum dots, to explore the boundary between quantum and classical physics."
Statement of Colin Duncan, Physical Sciences Application Specialist at Andor
"The iXon 885 low light EMCCD camera offers the highest sensitivity from a quantitative scientific digital camera, particularly at fast frame rates.
The megapixel sensor format and 8 x 8 μm pixel size presents an attractive combination of field of view and resolution, while a full resolution frame rate of 31 frames/sec is achievable. Unlike other EMCCDs, the 885 is non-aging and does not require routine EM gain recalibration with RealGain provides linear 1000-fold EM gain multiplication."
 Thomas Juffmann, Adriana Milic, Michael Muellneritsch, Peter Asenbaum, Alexander Tsukernik, Jens Tuexen, Marcel Mayor, Ori Cheshnovsky and Markus Arndt. "Real-time single-molecule imaging of quantum interference" Nature Nanotechnology 7, 297-300 (2012)