Quantum mechanical experiments with large objects What are some examples of quantum mechanical phenomena that have been observed not with electrons but rather with large real-life objects? In particular, what is the largest object for which the double slit experiment has been successfully performed with?
 A: As I say in my comment, there is probably a duplicate of this, that will turn up as soon as I  write this,  but as technology advances, perhaps it's out of date.
This answer concentrates as much on how you prepare "large" molecules, as I think that aspect is of interest in itself,  but we cannot approach the size of a virus or any tiny bacteria as yet, or for the foreseeable futures, as far as I know.
From Largest Molecule Double Slit.
These molecules are around 100 atoms in size, compare to the 180, 000 atoms in the smallest virus.

The relatively large phthalocyanine $C_{32}H_{18}N_8$ and derivative molecules $C_{48}H_{26}F_{24}N_8O_8$ 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. This was 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.
After separation from the film, the molecules were sent through a collimator to ensure they formed a beam before reaching the barrier, which had a number of parallel slits to produce the actual interference pattern. To prevent excessive interactions (primarily van der Waals forces) between the molecules and the edges of the slits, the researchers used a specially-prepared grating coated in silicon nitride membranes. Without such preparation, the molecules are likely to be deflected by ordinary interactions with the hardware.
After passing through the slits, the molecules' positions were recorded using fluorescence microscopy, which has both sufficient spatial resolution and fast response to detect when and where the molecules arrive. The positions of individual spots were measured to 10 nanometer accuracy. Additionally, the molecules lodged in the fluorescent screen, meaning their positions could be independently verified in the form of build-up at the experiment's end.

