Detecting Interference Patterns with Large Objects: The Double Slit Experiment

[john taylor]

Why is it so difficult to detect interference patterns with larger objects in the double slit experiment(e.g. bacteria)?

 

[PeroK]

Why is it so difficult to detect interference patterns with larger objects in the double slit experiment(e.g. bacteria)?

One way to look at it is to use the Heisenberg Uncertainty Principle for the y-direction is:

$\sigma_y \sigma_p \ge \frac{\hbar}{2}$

If we define the y-velocity as $v = \frac{p}{m}$, then we have:

$\sigma_v \ge \frac{\hbar}{2m} \sigma_y$

If $m$ is large, then you have very little uncertainty in the y-velocity of the particle. Effectively, you have a classical trajectory through the slit.

For an electron, $m$ is relatively small, so you get a larger uncertainty in the y-velocity, which is necessary for the interference pattern to emerge.

Note that this applies equally to single-slit experiments.

 

[john taylor]

what would it take to replicate the double slit experiment with larger objects such as microorganisms?

 

[PeroK]

what would it take to replicate the double slit experiment with larger objects such as microorganisms?

You can't. They are just too big. According to Wikipedia:

The experiment can be done with entities much larger than electrons and photons, although it becomes more difficult as size increases. The largest entities for which the double-slit experiment has been performed were molecules that each comprised 810 atoms (whose total mass was over 10,000 atomic mass units).[1][2]