3 ms·

The wave-effects depend on the fact that the wavelength is of a size that is comparable to the size of the object it's interacting with. Think about optics: o

by dhimes 15y ago

The wave-effects depend on the fact that the wavelength is of a size that is comparable to the size of the object it's interacting with. Think about optics: observing an interference or diffraction pattern is easier when the light interacts with very small structures (the patterns on a cd, for example), the same is true for "matter" waves. The catch is, the wavelength is of the order of h/momentum or h/(mass * velocity) where h (Planck's constant) is a really, really small number. When mass is something like an ordinary object, then the size of the "slits" becomes so small that we can't imagine how conduct the experiment.

jessriedel 15y ago
<s>This is mostly wrong</s>. When the de Broglie wavelength becomes smaller than the size of the object, observing quantum inference becomes harder, but it's certainly not impossible. In this experiment, the molecules (~10^2 atoms) are a few nano meters across and the de Broglie wavelength is a few hundredths of a nanometer. The same group is planning on future experiments with 10^6 atoms, where the wavelength will be much smaller than the object.
- dhimes 15y ago
  Um, how, exactly, is what I said wrong?
  - jessriedel 15y ago
    I more-or-less take back what I said. On first reading, your comment sounded to me like you were claiming that these effects go away for large objects rather than merely becoming very hard to see. In particular, this >When mass is something like an ordinary object, then the size of the "slits" becomes so small that we can't imagine how conduct the experiment. I think is misleading. Experiments demonstrating quantum interference of macroscopic objects are very easy to imagine and are limited by logistical concerns rather than fundamental physics. In particular, an experiment interfering objects large enough to see with the naked eye is very likely to occur this century, so I object to calling it "unimaginable". But you were mostly right. I'm sorry.
    - carbocation 15y ago
      The de Broglie wavelength of a baseball is something like 20 orders of magnitude smaller than a proton. If you imagine this to be something that might be probed in the next few centuries, I'd be interested to hear more.
      - jessriedel 15y ago
        I'd be willing to bet (e.g. longbets.org) that objects of size 10^15 amu (which is large enough to be visible to the naked eye) will be interfered in this century. Baseballs are 10 orders of magnitude larger. In any case, the point is that it's not a matter of the slits becoming too small. It's a matter of controlling environmental decoherence.
        carbocation 15y ago
        And this is one of the reasons I love HN. I would be interested in hearing more sometime. For example, if you were to write up a speculative blog post and submit it here...
    - dhimes 15y ago
      No sweat. I'm gathering that you are going into theory ;-) (I did also.) carbocation shares my point in a sister comment.

by dhimes 15y ago

jessriedel 15y ago

<s>This is mostly wrong</s>. When the de Broglie wavelength becomes smaller than the size of the object, observing quantum inference becomes harder, but it's certainly not impossible. In this experiment, the molecules (~10^2 atoms) are a few nano meters across and the de Broglie wavelength is a few hundredths of a nanometer. The same group is planning on future experiments with 10^6 atoms, where the wavelength will be much smaller than the object.

dhimes 15y ago
Um, how, exactly, is what I said wrong?
- jessriedel 15y ago
  I more-or-less take back what I said. On first reading, your comment sounded to me like you were claiming that these effects go away for large objects rather than merely becoming very hard to see. In particular, this >When mass is something like an ordinary object, then the size of the "slits" becomes so small that we can't imagine how conduct the experiment. I think is misleading. Experiments demonstrating quantum interference of macroscopic objects are very easy to imagine and are limited by logistical concerns rather than fundamental physics. In particular, an experiment interfering objects large enough to see with the naked eye is very likely to occur this century, so I object to calling it "unimaginable". But you were mostly right. I'm sorry.
  - carbocation 15y ago
    The de Broglie wavelength of a baseball is something like 20 orders of magnitude smaller than a proton. If you imagine this to be something that might be probed in the next few centuries, I'd be interested to hear more.
    - jessriedel 15y ago
      I'd be willing to bet (e.g. longbets.org) that objects of size 10^15 amu (which is large enough to be visible to the naked eye) will be interfered in this century. Baseballs are 10 orders of magnitude larger. In any case, the point is that it's not a matter of the slits becoming too small. It's a matter of controlling environmental decoherence.
      - carbocation 15y ago
        And this is one of the reasons I love HN. I would be interested in hearing more sometime. For example, if you were to write up a speculative blog post and submit it here...
  - dhimes 15y ago
    No sweat. I'm gathering that you are going into theory ;-) (I did also.) carbocation shares my point in a sister comment.