I'm a software / maths guy who would like to build a physical setup for generating quantum random numbers. I have no physics background, so bear with me.
Background
- The project is for a public exhibit, so it's important to me that the setup should look cool, or at least interesting, and should reveal something about how it works. API calls to a QRNG on the internet wouldn't serve that purpose. It also need to be safe to have around people, albeit perhaps in a glass case or whatever.
- I don't have a big budget or any physics or engineering skills, so I need something that doesn't require much skill or specialist equipment to build. I don't mind learning on the job, though, and I might be able to enlist the help of a physicist further down the line.
- I don't actually need the numbers generated to exhibit "true randomness", and I expect larger-scale effects (temperature, vibration etc) will interfere with the quantum ones; but I do want to be able to honestly say that photon emission times (or whatever) are influencing the results.
My very rough understanding is that this can be done by pointing a laser at a photocell; the resistance of the cell ought to vary slightly as the number of photons arriving varies. So if my software asks the photocell for its current value, and looks at the last few digits of that value, in theory the fluctuations ought to have a quantum origin.
Questions
- Is the setup I've described feasible and likely to work with low-cost components?
- If it's not, can you suggest another approach?
- If it is, how would I find out what strength of laser and sensitivity of photocell I need to get the effect? (That is, how "big" is the fluctuation in power?) What other technical things do I need to consider?
Note
Inevitably this question is a mixture of physics and engineering — I'm primarily looking for (in)validation of the general approach here, and will take specific engineering questions elsewhere if necessary. I'm hoping, perhaps in vain, that with a good definition of the physics, the engineering part can be accomplished by assembling a few stock components.
Best Answer
An alternative way to generate random numbers, that truly is quantum, and also quite easy: put a small radioactive source near a Geiger counter. Radioactive decay is a truly random event in the quantum sense, and is basically not subject to thermal noise at all.
For maximum visual impact, replace the Geiger counter with a cloud chamber. That way you can literally see the consequences of quantumly-random events. You could make random numbers from it using a web cam and some basic image processing.