A significant progress in large molecule interferometry

We have written several posts in this blog about the question of decoherence and thermodynamic limit. One of the crucial experiments to understand if a body made by a large number of molecules can become classical is through this ingenious way to do interferometry with large molecules. This idea has been realized by Anton Zeilinger and his group at University of Vienna using initially molecules of fullerene. The results were striking as they were able to prove the wave nature of these large molecules. The next step is to try to use more heavy bodies to do such an experiment. With their device, a Talbot-Lau interferometer, they were able to see wave behavior for fluorofullerene but in this case they obtained a visibility lower than expected (see here and here). They were unable to claim if this was a genuine new effect or rather a limitation of the experimental apparatus. Further analyses were needed but, mostly, the apparatus needed significant improvement to manage heavier molecules and to be sure in this way that any observed effect is a genuine one and not an artifact of the used device. Anyhow, I show here this picture that is really striking.

From this figure is blatantly evident that the expected curve is not in perfect agreement with measured points for fluorofullerene. But, as already said, the experimenters were not able to do any claim about this as these differences could be due to the interferometer.

Since then, all these activities have gone in the hands of Markus Arndt that worked with Zeilinger to these experiments. Arndt is full professor at University of Vienna and has taken in charge the not that easy activity to improve the apparatus to perform experiments with larger molecules. Recently Arndt and his group published a paper on Nature ( see here) where they showed a really significat improvement in the apparatus that should grant analysis of interferometry of very large molecules. We note in this way the complexity of this enterprise that required several years for the achievement. So, now the expectations are high to see interferometry with some unexpected kind of molecules and the possibility that Arndt and his group will do some breakthrough is surely high.


3 Responses to A significant progress in large molecule interferometry

  1. carlbrannen says:

    I’d be fairly satisfied with that data.

    It would be interesting if they discovered some distance or dimensino over which quantum effects disappeared. They talk about slower velocities being problematic because of the increase in time. I think that there are some excellent demonstrations of quantum effects over very long time intervals, but they always have to do with stuff travelling at c or close to it.

    Maybe a better parameter for wave function collapse is the proper time of the object.

  2. mfrasca says:


    Indeed, they are as the graph proves anyway a wave behavior of fluorofullerene. But if the effect would be genuine it would just prove losing of quantum behavior at increasing number of the atoms composing the molecule. A similar effect has been seen in NMR experiments with different complex moleules. See my post


    where a connection with Boltzmann’s hypothesis of molecular chaos is also given.


  3. carlbrannen says:

    My feeling on using thermodynamics to define the arrow of time is that it’s still purely a statistical argument and, over the very long term, all thermodynamics is reversible.

    I should point out that FQXi has an essay contest on the subject “The Nature of Time” and they’re giving away $50,000 in it so it is worth your time to type something up, I think.

    My essay on time, Density Operators and Time, (from which link you can get to the contest rules) is incompatible with my speculation in reply #1 about “proper time”. In the essay I’m arguing for a universal time, in addition to the 4th dimension of space-time as used by QM. So from the point of view of the essay, I’d say that the limitation is purely experimental, and does not depend on proper time or on mass, but instead is some very long universal time scale we cannot yet detect.

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