How can I understand quantum physics? All explanations I’ve seen are either:
those that dumb things down too much, and deliver almost no knowledge; or
those that assume too much familiarity with this kind of mathematics that nobody outside physics uses, and are therefore too frustrating.
I don’t think the subject is inherently difficult. For example quantum computing and quantum cryptography can be explained to anyone with basic clue and basic math skills. (example)
On the other hand I haven’t seen any quantum physics explanation that did even as little as reasonably explaining why hbar/2 is the correct limit of uncertainty (as opposed to some other constant), and why it even has the units it has (that is why it applies to these pairs of measurements, but not to some other pairs); or what are quark colors (are they discrete; arbitrary 3 orthogonal vectors on unit sphere; or what? can you compare them between quarks in different protons?); spins (it’s obviously not about actual spinning, so how does it really work? especially with movement being relative); how electro-weak unification works (these explanations are all handwaved) etc.
I don’t think the subject is inherently difficult. For example quantum computing and quantum cryptography can be explained to anyone with basic clue and basic math skills.
That’s because quantum computing and quantum cryptography only use a subset of quantum theory. Your link says, for example, that the basics of quantum computing only require knowing how to handle ‘discrete (2-state) systems and discrete (unitary) transformations,’ but a full treatment of QT has to handle ‘continuously infinite systems (position eigenstates) and continuous families of transformations (time development) that act on them.’ The full QT that can deal with these systems uses a lot more math.
I wonder if there’s a general trend for people who are interested in quantum computing and not all of QT to play down the prerequisites you need to learn QT. Your post reminded me of a Scott Aaronson lecture, where he says
The second way to teach quantum mechanics leaves a blow-by-blow account of its discovery to the historians, and instead starts directly from the conceptual core—namely, a certain generalization of probability theory to allow minus signs. Once you know what the theory is actually about, you can then sprinkle in physics to taste, and calculate the spectrum of whatever atom you want.
Which is technically true, but if you want to know about quark colors or spin or exactly how uncertainty works, pushing around |1>s and |2>s and talking about complexity classes is not going to tell you what you want to know.
To answer your question more directly, I think the best way to understand quantum physics is to get an undergrad degree in physics from a good university, and work as hard as you can while you’re getting it. Getting a degree means you have the physics-leaning math background needed to understand explanations of QT that don’t dumb it down.
I might be overestimating the amount of math that’s necessary—I’m basing this on sitting in on undergrad QT lectures—but I’ve yet to find a comprehensive QT text that doesn’t use calculus, complex numbers, and linear algebra.
Try Jonathan Allday’s book “Quantum Reality: Theory and Philosophy.” It is technical enough that you get a quantitative understanding out of it, but nothing like a full-blown textbook.
How can I understand quantum physics? All explanations I’ve seen are either:
those that dumb things down too much, and deliver almost no knowledge; or
those that assume too much familiarity with this kind of mathematics that nobody outside physics uses, and are therefore too frustrating.
I don’t think the subject is inherently difficult. For example quantum computing and quantum cryptography can be explained to anyone with basic clue and basic math skills. (example)
On the other hand I haven’t seen any quantum physics explanation that did even as little as reasonably explaining why hbar/2 is the correct limit of uncertainty (as opposed to some other constant), and why it even has the units it has (that is why it applies to these pairs of measurements, but not to some other pairs); or what are quark colors (are they discrete; arbitrary 3 orthogonal vectors on unit sphere; or what? can you compare them between quarks in different protons?); spins (it’s obviously not about actual spinning, so how does it really work? especially with movement being relative); how electro-weak unification works (these explanations are all handwaved) etc.
That’s because quantum computing and quantum cryptography only use a subset of quantum theory. Your link says, for example, that the basics of quantum computing only require knowing how to handle ‘discrete (2-state) systems and discrete (unitary) transformations,’ but a full treatment of QT has to handle ‘continuously infinite systems (position eigenstates) and continuous families of transformations (time development) that act on them.’ The full QT that can deal with these systems uses a lot more math.
I wonder if there’s a general trend for people who are interested in quantum computing and not all of QT to play down the prerequisites you need to learn QT. Your post reminded me of a Scott Aaronson lecture, where he says
Which is technically true, but if you want to know about quark colors or spin or exactly how uncertainty works, pushing around |1>s and |2>s and talking about complexity classes is not going to tell you what you want to know.
To answer your question more directly, I think the best way to understand quantum physics is to get an undergrad degree in physics from a good university, and work as hard as you can while you’re getting it. Getting a degree means you have the physics-leaning math background needed to understand explanations of QT that don’t dumb it down.
I might be overestimating the amount of math that’s necessary—I’m basing this on sitting in on undergrad QT lectures—but I’ve yet to find a comprehensive QT text that doesn’t use calculus, complex numbers, and linear algebra.
Try Jonathan Allday’s book “Quantum Reality: Theory and Philosophy.” It is technical enough that you get a quantitative understanding out of it, but nothing like a full-blown textbook.