3 ms·

> I don't even want to being to think about how or why amplitudes can be complex, and what you would possibly do with a complex probability I don't pretend to

> I don't even want to being to think about how or why amplitudes can be complex, and what you would possibly do with a complex probability I don't pretend to completely understand it either, but one crucial point here is that these complex amplitudes and their interactions are the "real" reality - they are "more real" than the normal probabilities we are used to, in that they are the things that actually exist in the universe and give rise to the 'normal' probabilities that we see. A lot of mental resistance to quantum mechanical ideas comes from thinking quantum mechanics is weird, instead of thinking quantum mechanics as normal and us being weird[1], because of the scale we live in and normally observe things in. [1] paraphrased from Eliezer Yudkowsky, Harry Potter and the Methods of Rationality, Ch 36

DuskStar 9y ago
Wow, I don't think I've ever seen someone cite fanfiction on HN before! But considering HPMOR introduced me to Worm [0] and Unsong [1], I really can't argue with doing so. Also a relatively good way to introduce college friends to rationalism, if for some reason recommending fanfiction to friends is easier than recommending lesswrong. [0] https://parahumans.wordpress.com/ https://parahumans.wordpress.com/ [1] http://unsongbook.com/ http://unsongbook.com/
- TeMPOraL 9y ago
  Well, if you want a non-fanfiction citation, there's this from Eliezer's regular non-fiction blogging: Reality has been around since long before you showed up. Don't go calling it nasty names like "bizarre" or "incredible". The universe was propagating complex amplitudes through configuration space for ten billion years before life ever emerged on Earth. Quantum physics is not "weird". You are weird. You have the absolutely bizarre idea that reality ought to consist of little billiard balls bopping around, when in fact reality is a perfectly normal cloud of complex amplitude in configuration space. This is your problem, not reality's, and you are the one who needs to change. http://lesswrong.com/lw/hs/think_like_reality/ http://lesswrong.com/lw/hs/think_like_reality/ (Really, a lot of insights in HPMOR are just reiterations of points Eliezer made in his Sequences.)
millstone 9y ago
Let's just say it's important to distinguish between what Yudkowsky considers to be quantum mechanical ideas, and what the equations and experiments actually say.
randomsearch 9y ago
To chime in on the probabilities issue: they aren’t really probabilities. Probability amplitudes are something we don’t really understand, but it is true that once we have set a basis for measurement, we can treat the amplitudes with respect to that basis as probabilities (written in complex form). However, this should not be interpreted as “quantum states are probabilistic mixtures of base states” - changing the measurement basis screws up that intuition. For example, if our new basis has one base vector that is equal to the quantum state we are measuring, suddenly our outcome is certain. Oh I wish I could explain this better.
- sundarurfriend 9y ago
  I feel like that explanation almost gets me there, but understanding it is just out of reach. Out of my many questions (for which I should probably seek books and videos), I'll ask this one: > changing the measurement basis screws up that intuition. For example, if our new basis has one base vector that is equal to the quantum state we are measuring, suddenly our outcome is certain. How does one change the measurement basis - is it a mathematical exercise done on paper, or is it an actual physical act? Is this what is meant by collapse of a wave function? Is this what we are doing when we 'measure' Schrodinger's cat at the end of the experiment and suddenly have a certain outcome?
  - randomsearch 9y ago
    Different measurement instruments have different bases. But we can also model our quantum system and imagine what would happen if we created a new instrument with any basis we choose. Measurement is indeed wave function collapse - when a quantum state in a superposition (with regards to our measurement basis) is measured and produces a definite answer.

DuskStar 9y ago

Wow, I don't think I've ever seen someone cite fanfiction on HN before! But considering HPMOR introduced me to Worm [0] and Unsong [1], I really can't argue with doing so. Also a relatively good way to introduce college friends to rationalism, if for some reason recommending fanfiction to friends is easier than recommending lesswrong. [0] https://parahumans.wordpress.com/ https://parahumans.wordpress.com/ [1] http://unsongbook.com/ http://unsongbook.com/

TeMPOraL 9y ago
Well, if you want a non-fanfiction citation, there's this from Eliezer's regular non-fiction blogging: Reality has been around since long before you showed up. Don't go calling it nasty names like "bizarre" or "incredible". The universe was propagating complex amplitudes through configuration space for ten billion years before life ever emerged on Earth. Quantum physics is not "weird". You are weird. You have the absolutely bizarre idea that reality ought to consist of little billiard balls bopping around, when in fact reality is a perfectly normal cloud of complex amplitude in configuration space. This is your problem, not reality's, and you are the one who needs to change. http://lesswrong.com/lw/hs/think_like_reality/ http://lesswrong.com/lw/hs/think_like_reality/ (Really, a lot of insights in HPMOR are just reiterations of points Eliezer made in his Sequences.)

millstone 9y ago

Let's just say it's important to distinguish between what Yudkowsky considers to be quantum mechanical ideas, and what the equations and experiments actually say.

randomsearch 9y ago

To chime in on the probabilities issue: they aren’t really probabilities. Probability amplitudes are something we don’t really understand, but it is true that once we have set a basis for measurement, we can treat the amplitudes with respect to that basis as probabilities (written in complex form). However, this should not be interpreted as “quantum states are probabilistic mixtures of base states” - changing the measurement basis screws up that intuition. For example, if our new basis has one base vector that is equal to the quantum state we are measuring, suddenly our outcome is certain. Oh I wish I could explain this better.

sundarurfriend 9y ago
I feel like that explanation almost gets me there, but understanding it is just out of reach. Out of my many questions (for which I should probably seek books and videos), I'll ask this one: > changing the measurement basis screws up that intuition. For example, if our new basis has one base vector that is equal to the quantum state we are measuring, suddenly our outcome is certain. How does one change the measurement basis - is it a mathematical exercise done on paper, or is it an actual physical act? Is this what is meant by collapse of a wave function? Is this what we are doing when we 'measure' Schrodinger's cat at the end of the experiment and suddenly have a certain outcome?
- randomsearch 9y ago
  Different measurement instruments have different bases. But we can also model our quantum system and imagine what would happen if we created a new instrument with any basis we choose. Measurement is indeed wave function collapse - when a quantum state in a superposition (with regards to our measurement basis) is measured and produces a definite answer.