Questions about quantum effects on dynamic systems.

[TheMadMonk]

We are now performing the two-slit experiment with objects as large and as complex as bacteria. So, exactly what happens with respect to internal metabolic processes during the time between the bacterium passing through the slit and hitting the detector? Suspended? Or do they continue apace in a manner which really boggles the mind.


What of entanglement and unstable particles. If we were to force a number of unstable particles into an entangled state, what happens to their decay profile? One in all in? Or do they enter a metastable state, preventing all breakdowns until the entanglement is first broken?

Synchronity or stasis?

[laconicsax]

1. At what point does something become too large to exhibit wave-particle duality?

Are there bacteria that have been shown to diffract in a double-slit experiment or are at least small enough for it to be a plausible result?

I was under the impression that buckyballs (~1 nm) were the largest objects to diffract in a double-slit experiment and the smallest bacteria are about 300 times larger than that (.3 µm). I've always been fascinated in where the upper limit is as far as an object being too large to diffract through the two slits.

[girl gone mad]

5. The technical term is decoherence.

It's the point at which the wave function appears to collapse and quantum effects are suppressed.

It's more complicated than just particle size. Decoherence can occur at the microscopic level and quantum effects have been observed at the macroscopic level.

Theoretically, you could perform the double-slit experiment with any object, but at large masses, the time, distances and number of particles needed make it completely impractical. For instance, to perform successfully w/ bowling balls would take 23 million times the known age of the universe and 10^38 bowling balls (conservatively, off the top of my head).

[girl gone mad]

6. For the sake of clarity..

a bowling ball would also decohere too rapidly for this experiment to be feasible, but my point was that, leaving aside the decoherence, there would be many other obstacles to performing double slit on more massive particles.

An electron is quantum coherent for several months, but once you get beyond the molecular scale, decoherence starts to occur within a fraction of a second.

[laconicsax]

7. Thanks!

:hi:

[Jim__]

2. Do you have a reference for a double slit experiment being performed with bacteria?

According to wikipedia, such an experiment is practically impossible:

Double-Slit Diffraction

Light passes through double slits and onto a screen resulting in a diffraction pattern. Is light a particle or a wave?

The Copenhagen Interpretation: Light is neither. A particular experiment can demonstrate particle (photon) or wave properties, but not both at the same time (Bohr's Complementarity Principle).

The same experiment can in theory be performed with any physical system: electrons, protons, atoms, molecules, viruses, bacteria, cats, humans, elephants, planets, etc. In practice it has been performed for light, electrons, buckminsterfullerene,<11><12> and some atoms. Due to the smallness of Planck's constant it is practically impossible to realize experiments that directly reveal the wave nature of any system bigger than a few atoms but, in general, quantum mechanics considers all matter as possessing both particle and wave behaviors. The greater systems (like viruses, bacteria, cats, etc.) are considered as "classical" ones but only as an approximation.

It's possible that this wiki article is outdated.

[qazplm]

4. yeah I'd like a link too

if we were performing double slit experiments on bacteria that would be HUGE news.

[caraher]

3. I think it's likely that "2-slit experiment" is meant almost metaphorically

Because the 2-slit experiment is so well-known, it's common to talk about experiments whose mathematical descriptions parallel the 2-slit experiment as "2-slit experiments." Usually there are not actually 2 slits and something passing through them, but rather two distinct "pathways" from an initial state to a final state for which there is some kind of quantum interference. Those pathways need not be physical pathways in real space.

One example would be 2-photon absorption where the two photons have different energies. There are 2 "paths," one in which the high-energy photon gets absorbed first and another in which the low-energy photon gets absorbed first. There's a direct analogy between those possibilities and, in the standard 2-slit experiment, going through one slit or the other. Though there are not literally 2 slits in the experiment one can talk about it in a similar way, and the math is similar as well. From the standpoint of fundamental physics there's not much difference even if they are very different physical systems and different experiments.