Mikko wrote:Simulation programs for EPR-type experiments have the problem that the simulated model is not obvious. In particular, it is not obvious whether locality is violated. Also the separation of laws of "nature" (i.e., of model), experimenter's choices and analysis of results. The latter two should be independently modifiable in order to allow comprehensive analysis of the simulation program.
The following recommendations enforce factual definiteness and locality. In addition, they separate laws of "nature" from analysis. In addition, the recommended file formats permit integrity checks.
The simulation model shall consist of two or three distinct programs: one that simulates the source that produces pairs of particles; and one or two that simulate detection of particles - the two detectors shall be simulated separately but the same program may be used.
The emission simulation program shall input the number of particle pairs to be emitted (e.g., from command line) and produce two files, below called particle files.
The mesurement simulation program shall input one of the particle files produced by the emission programs and a settings file, and output a result file.
In addition an analysis program is needed. It is not part of the simulation model and need not be created by the author of the simulation program. Any number of analysis programs may be used. An analysis program shall read two settings files and two result files and output the results of the analysis (to a file or stdout or display or whatever).
All files mentioned above shall be ASCII files that contain header lines, data lines, and a footer line in this order. The header and footer lines begin with the '#' charcter followed by one or more spaces. The data lines begin with one or more spaces followed by the number of particle pair (starting from 1) followed by one or more spaces. The rest of the line depends on the file type. Files may also contain blank lines but they mean nothing and shall be ignored. Any lines after the footer shall also be ignored.
The resul file shall have second, third, and fourth header lines that are exact copies of the second, third, and fourth header lines of the particle file. The fifth header line shall be an exact copy of the second header line of the settings file. Each data line shall end with result of the detection as a '+' or '-' character except if the particle is not detected at all, which shall be encoded with a '?' character.
These recommendations can be followed if the simulation model satisfies locality, factual definiteness and counterfactual definiteness. Other simulations should follow as many of these recommendations as the model allows.
gill1109 wrote:Mathematica is not eligible but probably alternatives can be found in Sage for those who wish to use symbolic computation.
gill1109 wrote: At each time step, two particles are generated at the source and go to the detectors. Two settings are supplied "from outside". Two outcomes are generated at the two detectors.
So each setting and each outcome has an externally determined identifier, which is just the run number: run 1, run 2, run 3, ...
Such experiments have probably never been done though some come close and I think that everyone agrees that this is a kind of ideal model.
In real world experiments with photons everything is happening (more or less) in continuous time. Particles leave the source at random times. They are detected by the detectors, sometimes, at times which cannot be predicted in advance. Settings are being switched rapidly according to some external scheme and each particular setting value is then in force for a whole time interval (till the next switch).
So the experiment generates four streams of random times with labels identifiying the kind of event.
My point here is that one can have different aims with a simulation model; it seems to me that both kinds of experiment are legitiate and interesting. There is not "one size fits all". But there are two main types. For the two different main types one can draw up a separate list requirements.
gill1109 wrote:Further recommendations: programs should be written in programming languages which are widely used and freely available and preferably open source and endorsed by international scientific bodies. They should run on different common computing platforms with only minor modifications. Programs should be written using the principles of "literate programming" and "reproducible research" ... the basic principle being that a human being can read and understand what is supposed to be going on, as well as a computer. Code should be made publicly available.
So: Java, C, C++, Python, R (open source implementation of S), Octave (open source implementation of Matlab) ... are eligible.
Random number generation should be done using reliable, well-documented, pseudo random generators and the implementation should include set / save / restore random seed facilities, so that a program can be run twice with identical inputs and generate identical output (even on different computers, even on different platforms).
Finally some comments on some of the issues Minkwe raised.
Clocked experiments (ie those with a definite "run number" 1, 2, ... identifiying subsequent, linked, particles settings and outcomes, can and do, both in the real world and in simulation models, generate outcomes "no detection" as well as +1, -1. I would suggest simply to code these with a 0. After all, it's up to the analyst how the data is going to be processed. So a "?" and a "0" are just as good as one another.
gill1109 wrote:Fred: any computer language is just a pocket calculator. The point is that everyone should be able to test and run scientific software to its limits. Requiring them to pay so many thousand dollar for commercial software for which the underlying code (even the algorithms) is secret is not scientific.
gill1109 wrote:I still have no idea why Minkwe is not prepared to divulge how Python sets, saves and restores random seeds, when you use its numerical library to simulate random variables.
minkwe wrote:gill1109 wrote:I still have no idea why Minkwe is not prepared to divulge how Python sets, saves and restores random seeds, when you use its numerical library to simulate random variables.
What are you talking about? Python is open-source and the documentation is available. Anyone can find out for themselves how Python saves and restores random seeds, whether or not I "divulge how" or not. The issue which you still fail to understand is that allowing a simulation to reproduce identical results is equivalent to remeasuring already measured particles which is practically impossible in real life. And it is precisely for this reason that Bell's inequalities are violated (the inability to measure counterfactual results) so unless you are trying to rig the game, you will cease insisting on such an irrelevant requirement.
Why don't you explain exactly why you want this requirement, and how it helps answer the question you are trying to answer.
gill1109 wrote:(a) so that software can be rigorously tested.
(b) in order to mathematically prove that a loophole free local realistic simulation programme cannot ever be written.
minkwe wrote:You want to force simulations to measure counterfactual terms by saving and restoring random number seeds so that you can proclaim that the CHSH was not violated.
minkwe wrote:The only important question is whether the QM correlations can be reproduced by a local realistic model, and whether experimental reports which were published in high-impact journals claiming to have proved "non-locality" or "non-reality" were valid, and whether it is possible contrary, to claims by famous physicists to simulate quantum phenomena in a local realistic manner. I'm sure you can find the quotes from Gull, Feynmann, etc, and I'm sure you have made such claims yourself that it is impossible to simulate quantum phenomena in a local-realistic manner.
gill1109 wrote:Are you saying that the EPR paper should never have been published because no-one ever had done, nor ever will do, the EPR experiment, exactly as described there?
Are you saying that the mathematical theorem that S^0, S^1, S^3 and S^7 are the only parallelizable spheres is not true, because 7 dimensional spheres do not exist in the three dimensional space of a physicist's laboratory?
Please try to use your imagination, please try to use your capacity for abstract and analytic thought.
And tell me, what do you think: do you think it's possible to write a local realist computer simulation of a *clocked* experiment with no "non-detections", and which reliably reproduces the singlet correlations? (By reliably, I mean in the situation that the settings are not in your control but are delivered to you from outside; the number of runs is large; and that this computer program does this not just once in a blue moon, by luck, but most times it is run on different people's computers.)
gill1109 wrote:minkwe wrote:You want to force simulations to measure counterfactual terms by saving and restoring random number seeds so that you can proclaim that the CHSH was not violated.
No. You are *completely* missing the point.
gill1109 wrote:Incidentally, that might be true for photons, but it is false for the colourful exploding balls in Christian's proposed experiment. In fact he asks the experimenters to measure the spins of both hemispheres in all directions all at once!
Joy Christian wrote:gill1109 wrote:Incidentally, that might be true for photons, but it is false for the colourful exploding balls in Christian's proposed experiment. In fact he asks the experimenters to measure the spins of both hemispheres in all directions all at once!
Not true! Where did you get such an absurd idea from? Please read my papers carefully: http://libertesphilosophica.info/blog/e ... taphysics/.
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