Quantum computing has made significant advances in recent years, but issues of cost and complexity have kept it mainly in the realm of research. A newly proposed system from a group of Air Force and Florida Atlantic University researchers isn't likely to make quantum computing go mainstream, but it could bring the cost of building such systems down because it could use off-the-shelf components. The system would use photons in place of electrons, but photons don't easily interact with each other and so don't yield up useful information easily. The traditional fix is to use a tool called an inteferometer to manipulate the photons, but that solution is relatively expensive and the tools themselves are finicky — to say nothing of the fact that it requires "cascades" of them to build a quantum computer that utilizes photons.
The proposed solution is to simply transfer the work done by the inteferometer to a hologram permanently encoded on a pane of "OptiGrate" glass. It would solve the issue of having to calibrate inteferometers, but it would also remove that option entirely as the holograms would be unchangeable on the glass. In other words, the programming would have to be hard-coded. That doesn't mean that a quantum computer built using this method couldn't be useful for certain tasks like quantum error correction, but it does mean that it would be difficult to scale as the panes of glass would have to be rather large to carry out anything beyond "low-dimensional quantum computations" — though stacking the holographic plates could help.
The researchers say they are "well along in understanding these devices from a theoretical perspective," but unfortunately there aren't any prototypes built yet. Still, the system described here would be "resistant to environmental factors" and less expensive, so hopefully a prototype won't be too far off.