Matter Holograms: What would be involved?

Question

With photons, holograms are easy: shine laser light at a slit with an appropriate width, get a diffraction.

Shine laser light that is in-phase with the source light at the right spot downstream of the diffraction, at the correct angle... and place holographic photo-sensitive material at the point of light overlap.

Record the peaks and troughs of the light waves, and you have a hologram.

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All over the place, you will find statements to the effect that all matter can be treated like a wave under certain conditions.

So it seems like this should be possible.

Suppose you did it with electrons. What would happen if you diffracted an electron and recombined it with an in-phase twin shot through a magnetic field that "reflected it"?

And what would change if you placed an object in between the diffraction step, and the reference beam/electron recombination?

Answer 1

You are right that it is possible to make holograms using particle waves. The challenges are: 1) obtain a sufficiently spatially and temporally coherent particle beam, and 2) find a recording material that interacts with the particles, resulting in a change in the material that makes it interact differently with the particles (e.g., absorb or reflect differently).

One straightforward approach to making a coherent beam of electrons would be to use a tungsten point, charged to a high voltage, to emit electrons. Because they are emitted from a point they are spatially coherent. Blocking all electrons that don't pass through a distant hole will produce a nearly collimated beam.

A way to make the electrons temporally coherent is to pass them through a magnetic field that deflects them by an amount that depends on their momentum, so they get sorted out by momentum (and therefore by wavelength) downstream.

In the recording setup it's important to make sure electrons of the same momentum come together at each point on the recording medium.

A very simple recording material is electron beam resist, used in the manufacturing of ICs. Using well-known microlithography techniques, the exposed regions of an interference pattern can be converted to metal stripes opaque to an electron beam, and the unexposed regions converted to electron-transparent form.

Bottom line: an electron wave hologram isn't easy, but can be (and has been) done. It will work very much like an ootical hologram.