pcalau12i

A lot of the confusion around quantum mechanics comes from misleading cartoons about the double-slit experiment which don’t occur in reality. They usually depict it as if the particle produces a wave-like interference pattern when you’re not looking, and two separate blobs like you’d expect from particles when you look. But, again, you have never seen that, I have never seen that, no physicist has ever seen that. It only exists in cartoons.

In fact, it cannot occur because it would violate the uncertainty principle. The reason you get a spread out pattern at all is because the narrow slits constrain the particle’s position so its momentum spreads out, making its trajectory less predictable. There is simply no way you can possible have the particles both pass through narrow slits and form two neat blobs with predictable trajectories, because then you would know both their position and momentum simultaneously.

What actually happens if you run the calculation is that, in the case where you measure the which-way information of the particle, the particle still forms a wave-like pattern on the screen, but it is more akin to a wave-like single-slit diffraction pattern than an interference pattern. That is to say, it still gives you a wave-like pattern.

It is just not true that particles have two sets of behavior, “particle” and “wave” depending upon whether or not you’re looking at them. They have one set of equations that describes their stochastic motion which is always wave-like. All that measuring does is entangle your measurement device with the particle, and it is trivial to show that such entanglement prevents the particle from interfering with itself when considered in isolation from what it is entangled with.

That is all decoherence is. If you replace the measuring device with a single second particle and have it interact such that it becomes entangled with that particle, it will also make the interference pattern disappear. Entanglement spreads the interference effects across multiple systems, and if you then consider only subsystems of that entangled system in isolation then you would not observer interference effects.

a secret third thing

I’m not sure what you mean by “turning into into a classical random number.” The only point of the card is to make sure that the sampling results from the simulator are truly random, down to a quantum level, and have no deterministic patterns in them. Indeed, actually using quantum optics for this purpose is a bit overkill as there are hardware random number generators which are not quantum-based and produce something good enough for all practical purposes, like Intel Secure Key Technology which is built into most modern x86 CPUs.

For that reason, my software does allow you to select other hardware random number generators. For example, you can easily get an entire build (including the GPU) that can run simulations of 14 qubits for only a few hundred dollars if you just use the Intel Secure Key Technology option. It also supports a much cheaper device called TrueRNGv3 which is a USB device. It also has an option to use a pseudorandom number generator if you’re not that interested in randomness accuracy, and when using the pseudorandom number generator option it also supports “hidden variables” which really just act as the seed to the pseudorandom number generator.

For most most practical purpose, no, you do not need this card and it’s definitely overkill. The main reason I even bought it was just because I was adding support for hardware random number generators to my software and I wanted to support a quantum one and so I needed to buy it to actually test it and make sure it works for it. But now I use it regularly for the back-end to my simulator just because I think it is neat.

I own a quantum random number generator on a PCie card that uses optical effects for random number generation. It cost me over $2000. I use it for quantum computer simulations.