[3/4] > You could also massively simplify particle interactions to make some reasonable gameplay; perhaps even simulate a quantum computer. Do get in touch wit

[3/4] > You could also massively simplify particle interactions to make some reasonable gameplay; perhaps even simulate a quantum computer. Do get in touch with me if you want to do this; I’d be keen to help. If you can find a way to simulate an arbitrarily-sized quantum computer with a reasonable amount of computing, you will get famous. A few particles should be possible but it won't scale well. You're right to worry about how to draw it. You might consider (fixed-in-space) spin systems instead, where you can draw the density matrix with (relative) simplicity. But then you lose the moving-around-in-space intuition. > Feynman dedicates a lot of his book to two state systems, because these are ultimately responsible for the strong and weak nuclear forces. > Nuclear forces arise when you vary the size of the system, and the two possible stationary states display slightly different energy characteristics. This means the system has a lower energy at a certain size. Oy. This is wrong. Two state systems are interesting in-and-of-themselves because you can exactly solve them, they have many actual instatiations in nature (in fact, anything you might consider making a qubit out of!), and they provide toy models for many kinds of other physical systems. Nuclear forces do not arise from two state systems. There is a pecularity in nuclear physics---the proton and the neutron look (almost) exactly the same. OK, they have different electric charge, but nuclear force doesn't care about electromagnetism. What's interesting is that they have almost exactly the same mass: m_Neutron = 939 MeV, m_Proton = 938 MeV. Well, that's quite surprising! Why should that be? Most particles we know have dramatically differing masses (eg. m_electron = 0.511 MeV, etc). So, what's making these masses come out the same? Moreover, people noticed empirically that the interaction between protons and neutrons seemed to look roughly the same (once you account for electromagnetism). This led people to hypothesize a symmetry called isospin symmetry---the symmetry between protons and neutrons [isospin]. You can make a lot of progress by assuming that protons and neutrons form two-state system and that the nuclear force doesn't care which state you're in. Then, you can incorporate the slight differences on top. In fact, you can get a lot farther once you have this idea in hand. You realize that the pions form an iso-triplet, the delta baryons form an iso-fourplet, etc [fourplet]. Then you find particles with strangeness, and you really get going. You wind up recognizing deeper underlying patterns that reveal beautiful symmetry. Isospin symmetry is not a true symmetry of nature, but it's a very good approximation, and it's related in some ways to weak isospin [weak].