This is interesting, and may have useful applications, but it's not a validation of quantum computing as it's usually conceived, in that it appears to be doing the computation with multiple photons, so it could be relying on different photons being in different states. True quantum computing relies on the Copenhagen interpretation of the current framework for Quantum Mechanics: that the probability distributions it operates on are, in some sense, real, rather than merely reflections of our uncertainty regarding the system's state. It assumes that by operating on a superposition of these probability distributions within a single system, multiple computations can be performed simultaneously. In the system described, that apparent superposition in the probability distributions is potentially being "faked" by superposition in the concrete, individual states of the multiple photons involved in the computation.

But I'm biased. I'm quite dubious about the Copenhagen interpretation of Quantum Mechanics, and I think quantum computation is a reductio ad adsurdum of its conclusions, which may one day be used in its experimental disproof.

This is a validation of quantum computing as normally conceived. Photons are just as valid a quantum particle as anything else -- most importantly they can exhibit entanglement, which classical "light waves" can't.

You're begging the question. I'm aware that most physicists believe photon states can be entangled. My point is that it's not clear that quantum entanglement is used in this computation. There are so many photons being used that it would be possible for the probability waves to be approximated by the frequency distribution of the photons' states.