Particle-Wave Duality Demonstrated With Largest Molecules Yet

An anonymous reader tips news that researchers have successfully demonstrated particle-wave duality in molecules that have masses of 514 and 1,298 atomic mass units. The academic paper can be found in Nature Nanotechnology. "Thomas Juffmann et al. fired molecules composed of over 100 atoms at a barrier with openings designed to minimize molecular interactions, and observed the build-up of an interference pattern. The experiment approaches the regime where macroscopic and quantum physics overlap, offering a possible way to study the transition that has frustrated many scientists for decades. ... The relatively large phthalocyanine (C32H18N8) and derivative molecules (C48H26F24N8O8) have more mass than anything in which quantum interference has previously been observed. To have wavelengths that are relatively large compared to their sizes, the molecules need to move very slowly. Juffmann et al. achieved this by directing a blue diode laser onto a very thin film of molecules in a vacuum chamber, effectively boiling off individual molecules directly under the beam while leaving the rest unaffected. ... The researchers observed the particle nature of the molecules in the form of individual light spots appearing singly in the fluorescent detector as they arrived. But, over time, these spots formed an interference pattern due to the molecules' wavelike character.'"

Movie

[buchner.johannes]

The mentioned researchers in Vienna [quantumnano.at] created this movie where you see both the particle nature as well as the interference pattern:

https://www.youtube.com/watch?v=vCiOMQIRU7I [youtube.com]

Re:DNA is large

[Guppy06]

DNA is a polymer, orders of magnitudes bigger than the molecules they're talking about

Re:Is there any volunteer?

[semi-extrinsic]

Scientists are currently trying [sciencemag.org], albeit with somewhat smaller objects than a person. What you should understand is that the tunneling probability is exponentially damped in both the width of the barrier and the size of the object.

Already for a hydrogen nucleus tunneling through the (electrostatic) potential barrier presented by another hydrogen nucleus, the probability is around 10^-30 (if memory serves correctly). This fact is what keeps the sun burning for billions of years, and not exploding like a hydrogen bomb in a split second, since it limits the rate of fusion processes in the sun.

Re:DNA is large

[reverseengineer]

It would be very difficult to test DNA in the manner described in the paper- it would appear that the specific molecules chosen have a number of attributes that make them suitable for the double-slit experiment. They are fluorescent dyes, which makes them very sensitive to detection, they can be vaporized without thermal decomposition, they are neutral molecules, and they have multiple symmetries so that there isn't a preferred orientation. DNA molecules would be destroyed by the heat sources they used, and the highly charged DNA molecule is likely to interact with the atoms of the diffraction grating in a classical electrostatic manner. Some other biomolecules might be more suitable- phthalocyanine is similar in structure to heme and chlorophyll.

Re:Holy Hell that's large

[DMiax]

Maybe you thought that.

Among the last few generations of physicists it is generally believed that everything is quantum from an elementary particle to whole planets. It's just very difficult to cool planets down to where the thermal length is smaller than their de Broglie's length. Not to mention creating a coherent planet gun and detector... But there was no reason to believe it is fundamentally impossible.

Re:Richard Feynman

[DMiax]

There is no particle-wave duality. Every particle is only a wave and sometimes, if you look from very far (or at high temperatures) it seems to behave as a point-like object.

In any case it is not like path integrals are alternative to the normal schroedinger wavefunction formulation. See the work of Dyson for that, or simply the Feynman-Kac formula. At the fundamental level path-integrals ar just combinations of double-slits experiments in a very abstract space (Trotter's formula).

And yes, in the path integral a particle interferes with itself. You'll notice that you have to take into account and sum paths going through different slits.

I do work in the path integral formulation because I think it is more elegant, but it is not an alternative to the "traditional" wavefunction approach (hey, path integral is not exactly new anymore). It is the same as choosing cartesian or spherical coordinates.

The tagline is: path integrals do not describe different physics.

Macroscopic wave–particle duality

[advid.net]

Wave-particle duality has yet been observed with much bigger objects, on different physical basis but with astonishingly equivalent behaviour.

A 'walking' drop on a liquid surface behave like a particle with wave properties: diffraction, interference patterns, vibration quantization.

First, in a vibrating container they put a liquid like silicon oil, vibrations are just bellow the Faraday instability threshold. Then a drop of the same liquid is dropped on the surface, but it does not coalesce, it bounces. And further bounces make a static wave pattern on the liquid surface just bellow the drop and its immediate neighborhood. As the spike grows, instability increases and the drop slides down the spike, and start moving horizontally.

Then they have a combo object drop+wave pattern moving at 1/10th the speed of wave in this liquid, straight. They call it a walker.

What is really amazing is that the wave pattern below the drop has some kind of memory: it has accumulated energy from several drop bounces. It can also make the drop see "forward", as the small wave pattern bounces back from nearby obstacles. So the drop is "aware" of its environment and "recall" the path it has followed.

Diffraction is observed and explained by the multiple reflexions the wave makes when the drop passes through a small hole, randomizing the wave pattern and the angle of the path afterward. Interference patterns observed are explained a la de Broglie: as the drop passes through one of the two holes, its associated wave passes through both, carrying forward the message of the second hole to the drop and changing the statistical repartition of the drop's path direction. One more stunning result: they are circling the drop by moving the container (Coriolis), then the associated wave adopts a discrete series of pattern, depending on the speed and radius. Very much like the energy quantization of electrons.

English (and French) abstract [archives-ouvertes.fr]
A short article (French but it has photos and formulas) [sfpnet.fr]
Full thesis (French,10Mb)" [archives-ouvertes.fr]

Re:Half photons

[ThePeices]

Dude, you cannot have half a photon. Its at least one or none.

You can have a photon with half the energy of another photon, but you cannot have half a photon.

Ill try another tact....If you had a hole, and filled in half of it, you would be left with a hole. There is no such thing as half a hole, but there is such thing as a hole half the size of another hole.

Not the best analogy, but it all boils down to one simple fact. A quantum of light ( a photon ) is the smallest unit of light.

Re:Richard Feynman

[blutfink]

I do not believe in particle-wave duality. I believe in Feynman's path integral formulation.

This is not related in the way you might think it is. The former is a philosophical problem in the interpretation of quantum mechanics, the latter is one of several ways of resolving this problem in practice.

Re:Is there any volunteer?

[semi-extrinsic]

Alright, let me clarify what I meant. In fusion, the main factors in determining the reaction speed is the energy and the density. While the energy is comparable in the sun and a hydrogen bomb, the density is 2 orders of magnitude higher in a hydrogen bomb than at the sun's core. The tunneling probability is exponentially sensitive to the density; so sensitive that a third of the way out from the sun's core, fusion can no longer happen. This means that those 2 orders of magnitude are translated into 20 orders of magnitude slower explosion. At that point, I wouldn't call it an explosion.

Just to highlight this point: the power production per volume at the sun's core is 280 W/m^3. This is less than for a human being, it's roughly the same power as a crocodile produces per volume.

TL;DR: You're saying that the smoldering pile of flour on my kitchen bench is exactly like a dust explosion. I beg to differ.