In Mcintyre's QM book he writes:

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  1. What does he mean by "a macroscopic object strongly interacts with the environment" for there to be no interference?
  2. Why/how does the wave function of macroscopic objects suffer from decoherence? I assumed it had to do with the de Broglie wavelength:

and hence the mass and the velocity of a macroscopic object is relatively "big" the wavelength would be very small and would not physically possible to achieve. Furthermore, the lattice constant has a similar magnitude as the wavelength and that would also be impossible to have e.g. a 10^-37m lattice constant opening. Though it seems that this is not necessarily the reason why.


Aside from decoherence arguments, there is a huge reason why the double-slit experiment is very unlikely ever to be done successfully with baseballs. The DS experiment requires production of a large number of particles (e.g., photons or baseballs) whose quantum states are nearly identical. That is easy with photons because they have a relatively small number of degrees of freedom and they are easy to generate over and over with a single source. With baseballs the number of degrees of freedom is gigantic (several for each atom in the baseball).

Note: the single-photon DS experiment uses single photons, but still requires a very large number of photons, one at a time.

  • $\begingroup$ Thanks for the insight. What do you mean by degrees of freedom here? Meaning also including atoms vibrating? I.e.: en.wikipedia.org/wiki/… $\endgroup$ – mikanim May 25 '19 at 17:09
  • $\begingroup$ Degrees of freedom include anything that can be changed independently. Or we could say that the number of degrees of freedom is the number of values needed to completely specify the state of the system. Atoms vibrating, atoms repositioned, etc., all constitute degrees of freedom. Two identical baseballs, for quantum mechanical purposes, would need to be identical down to the locations and states of the molecules in the fibers of the leather "skin", not to mention the interior of the ball. Buckyballs at low temperature have few degrees of freedom: the atoms are in fixed relative locations. $\endgroup$ – S. McGrew May 25 '19 at 17:49

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