8 ms·

A free introduction to quantum computing and quantum mechanics

257 points by lisnake 6y ago

sfg 6y ago
"Quantum Country is a new kind of book. Its interface integrates powerful ideas from cognitive science to make memory a choice." What were the powerful ideas?
- sgdpk 6y ago
  Spaced repetition [1], they send you questions over increasing time periods to consolidate what you learned in the long term. [1] https://en.wikipedia.org/wiki/Spaced_repetition https://en.wikipedia.org/wiki/Spaced_repetition
  - sfg 6y ago
    Thank you.
  - da39a3ee 6y ago
    Unfortunately the questions are utterly superficial and laughably different from the sort of thinking you need to do to understand how a 2-dimensional complex vector space is involved in quantum physics and quantum computing. I say that not as a physicist/mathematician looking down at the oiks trying to underastand this stuff, but as one of the oiks.
    - currymj 6y ago
      i tend to trust Nielsen on this one, who literally wrote the book on quantum computing and has spent years teaching it to people. his philosophy is that the biggest obstacle to understanding is memorization of basic concepts and notation.
    - acs5 6y ago
      You're right that the spaced repetition questions are different from the really interesting questions, but that's the point. They're supposed to be aids in internalising the "lower-level"/"boring" terms, definitions, properties, etc., which is necessary to be able to follow along.
    - kirrent 6y ago
      Of course they are. By design the flash cards are small atomic pieces of knowledge that can be answered simply. If the grand overarching concept is a web of interconnecting ideas, then the flashcards are supposed to help you maintain that by making sure you don't forget the small ideas the structure is made of. It's also by design that some of the questions are, as you say, laughably simple. It's to catch people who aren't properly engaging with the text as early as possible. Nielsen and Matuschak are sensible to these sorts of critiques. Quantum country is part experiment after all and they've been learning, adjusting, and experimenting with what works best. If you want a bit of context of where they've come from and where they want to go, I recommend this: https://numinous.productions/ttft/ https://numinous.productions/ttft/
Mvandenbergh 6y ago
To me (but then I already know a lot about both of these topics) the format is actually much more interesting. Although it looks like the material is well presented. It does make sense that if we're going to have learning interfaces they have spaced repetition built in rather than requiring users to do that themselves. Looking forward to reading through.
SiebenHeaven 6y ago
Beware, there is a sign-in wall on this "free" introduction that comes up after a couple of topics. Edit: this seems to be the case only on the mobile version
- Koshkin 6y ago
  I would like to coin the term "A free (as in cheese)..."
  - keanebean86 6y ago
    Instead of an open door policy it's a closed but unlocked door policy.
- montyevans 6y ago
  The intent behind the sign-in seems to be to allow you to participate in the built-in SRS system for learning the material. Obviously there's no guarantee that behind the scenes your email is not being sold off to NefariousMarketers Inc., but given the past projects and work of both authors, that seems perhaps unlikely.
eightysixfour 6y ago
One of the creators of this, Andy Matuschak, is the only person I support on Patreon. I really believe that we are just now starting to scratch the surface of the learning opportunities that computers present to us and Quantum Country was an interesting step forward in that direction. It is worth looking at some of his previous work with Khan Academy as well, cool stuff.
deleted 6y ago
[deleted]
342637 6y ago
This is a great study resource. A downside is there are no solutions to check your work, or look up if you get stuck. I’d imagine a lot of people reading this wouldn’t necessarily be university students with a professor to ask questions to, so such a resource would be useful.
da39a3ee 6y ago
This is a really great resource that introduces some fairly sophisticated ideas. I'm about to be negative but I genuinely mean that; I'm planning to go back to it. I was finding it took time to take in the ideas about C^2. However > Presented in a new mnemonic medium which makes it almost effortless to remember what you read This is just nonsense and quite distracting, even irritating. Quantum computing and quantum mechanics is hard and involves sophisticated concepts. The spaced repetition questions are utterly superficial and represent unhelpful dumbing down. Apologies for the rant and slightly silly comparison between quantum physics and a programming language but the same goes for the Rust book. Rust is a hard language with sophisticated ideas. Despite the best intentions of the nice people at Mozilla, no amount of dumbing down changes that. And patronizing readers does not make the resource more approachable to women and under-represented minorities, unless you believe that those groups need to be patronized. > The set of curly brackets, {}, is a placeholder: think of {} as little crab pincers that hold a value in place.
- newswasboring 6y ago
  > And patronizing readers does not make the resource more approachable to women and under-represented minorities, unless you believe that those groups need to be patronized. That came out of the blue. Am I missing something? Did mozilla make such an attempt to patronize minorities?
  - steveklabnik 6y ago
    I think your parent is suggesting that this whimsical example is patronizing. Some fun history here: Ruby uses #{} for string interpolation. I used to teach Ruby to folks as a job, and I believe that my boss, Jeff Casimir, said that they looked like lobster pincers in one of our classes. (If Jeff reads this and that's incorrect, my apologies!) Years later, when I was writing this part of the book, I remembered this analogy, and we had the whole crab thing going on with Rust, and I thought it was a fun thing. So I put it in the book. Some people find whimsy inherently patronizing or something. I dunno. It's an offhanded fun comment, not some sort of desire to "dumb things down" for anyone. We don't write anything with the intention of dumbing things down.
boromi 6y ago
Anyone else find the navigation tricky? I wanted to flip through the book to find out the breadth of topics.
swebs 6y ago
>At least in popular media accounts, a very common description is that a state like 0.6∣0⟩ + 0.8∣1⟩ is “simultaneously” in the ∣0⟩ state and the ∣1⟩ state. >I must confess, I don’t understand what people mean by this. I think they're just trying to tie it to Schrödinger's cat somehow since that's the only other topic that seems to be covered in pop science.
Q_is_4_Quantum 6y ago
Note its not strictly-speaking necessary to learn any linear algebra to "understand" quantum computing, there is a very simple but universal set of string-rewriting rules. I realise for this audience most people wouldn't get much from it, but I find these rules useful for explaining quantum theory without annoying and fluffy analogies to high school students. You can find the rules in my book _Q is for Quantum_ - Part I which covers quantum computing is a free download on the book website (and the rest will be if I ever get around to producing a corrected pdf, bleh, but if you read part I and don't want to pay for the rest let me know and I'll get it to you...)
- gus_massa 6y ago
  Are you sure the easy rewriting rules are not just 2x2 matrix multiplication?
  - abdullahkhalids 6y ago
    I looked at the book and it is. His way is perhaps useful for not scaring off amateurs from learning quantum theories, but ultimately he is tricking them into learning a part of linear algebra without a foundation upon which more complex concepts can be built.
    - magsnus 6y ago
      I hate people that trick others in to learning stuff. :) This book really looks nice and short to me and I really wish the other parts comes online to.
    - Q_is_4_Quantum 6y ago
      Actually its not quite that simple. The approaches are "equivalent" (in terms of operational/statistical predictions) but not "isomorphic" (even if we restrict the regular linear algebra approach to the same gates as I use in the book). Basically (because of not implementing normalization/unitarity) in certain situations the "mist" retains a count of the number of "Feynman paths" that led to the output state. For example, concatenate two PETE boxes (hadamard gates) and the output is [W,W], concatenate four and its [W,W,W,W]. Operationally identical (you only observe the ball to be certainly white!) and applying a suitable simplification rule you "drop the extras" of course. But if someone (unlike me!) wants to think of these states as having ontological status maybe they would think the distinction is relevant. A much more interesting example of something similar happens in the Deutch-Hayden version of Heisenberg picture style quantum theory. There from looking at the "state of the world" you can determine which total unitary evolution occurred to get you there. In the Schroedinger picture, if I give you the inital and final states there are many possible unitaries that get you between them. Its possible to go further and come up with versions where not only the total unitary connecting initial and final state is discernable, but also the sequence of Hamiltonian's that implemented it are too. These things are mainly of interest to people in foundations of course (since they like to play the game of blurring the line between our math and what is "really out there"). I tried to be very careful in the book to maintain the distinction.
kensavage 6y ago
I thought quantum computing was something of science fiction? I still can’t wrap my head around it so as far as I’m concerned it’s hullabaloo.
zeepzeep 6y ago
Are other intros not free?!

257 points by lisnake 6y ago

sfg 6y ago

"Quantum Country is a new kind of book. Its interface integrates powerful ideas from cognitive science to make memory a choice." What were the powerful ideas?

sgdpk 6y ago
Spaced repetition [1], they send you questions over increasing time periods to consolidate what you learned in the long term. [1] https://en.wikipedia.org/wiki/Spaced_repetition https://en.wikipedia.org/wiki/Spaced_repetition
- sfg 6y ago
  Thank you.
- da39a3ee 6y ago
  Unfortunately the questions are utterly superficial and laughably different from the sort of thinking you need to do to understand how a 2-dimensional complex vector space is involved in quantum physics and quantum computing. I say that not as a physicist/mathematician looking down at the oiks trying to underastand this stuff, but as one of the oiks.
  - currymj 6y ago
    i tend to trust Nielsen on this one, who literally wrote the book on quantum computing and has spent years teaching it to people. his philosophy is that the biggest obstacle to understanding is memorization of basic concepts and notation.
  - acs5 6y ago
    You're right that the spaced repetition questions are different from the really interesting questions, but that's the point. They're supposed to be aids in internalising the "lower-level"/"boring" terms, definitions, properties, etc., which is necessary to be able to follow along.
  - kirrent 6y ago
    Of course they are. By design the flash cards are small atomic pieces of knowledge that can be answered simply. If the grand overarching concept is a web of interconnecting ideas, then the flashcards are supposed to help you maintain that by making sure you don't forget the small ideas the structure is made of. It's also by design that some of the questions are, as you say, laughably simple. It's to catch people who aren't properly engaging with the text as early as possible. Nielsen and Matuschak are sensible to these sorts of critiques. Quantum country is part experiment after all and they've been learning, adjusting, and experimenting with what works best. If you want a bit of context of where they've come from and where they want to go, I recommend this: https://numinous.productions/ttft/ https://numinous.productions/ttft/

Mvandenbergh 6y ago

To me (but then I already know a lot about both of these topics) the format is actually much more interesting. Although it looks like the material is well presented. It does make sense that if we're going to have learning interfaces they have spaced repetition built in rather than requiring users to do that themselves. Looking forward to reading through.

SiebenHeaven 6y ago

Beware, there is a sign-in wall on this "free" introduction that comes up after a couple of topics. Edit: this seems to be the case only on the mobile version

Koshkin 6y ago
I would like to coin the term "A free (as in cheese)..."
- keanebean86 6y ago
  Instead of an open door policy it's a closed but unlocked door policy.
montyevans 6y ago
The intent behind the sign-in seems to be to allow you to participate in the built-in SRS system for learning the material. Obviously there's no guarantee that behind the scenes your email is not being sold off to NefariousMarketers Inc., but given the past projects and work of both authors, that seems perhaps unlikely.

eightysixfour 6y ago

One of the creators of this, Andy Matuschak, is the only person I support on Patreon. I really believe that we are just now starting to scratch the surface of the learning opportunities that computers present to us and Quantum Country was an interesting step forward in that direction. It is worth looking at some of his previous work with Khan Academy as well, cool stuff.

deleted 6y ago

[deleted]

342637 6y ago

This is a great study resource. A downside is there are no solutions to check your work, or look up if you get stuck. I’d imagine a lot of people reading this wouldn’t necessarily be university students with a professor to ask questions to, so such a resource would be useful.

da39a3ee 6y ago

This is a really great resource that introduces some fairly sophisticated ideas. I'm about to be negative but I genuinely mean that; I'm planning to go back to it. I was finding it took time to take in the ideas about C^2. However > Presented in a new mnemonic medium which makes it almost effortless to remember what you read This is just nonsense and quite distracting, even irritating. Quantum computing and quantum mechanics is hard and involves sophisticated concepts. The spaced repetition questions are utterly superficial and represent unhelpful dumbing down. Apologies for the rant and slightly silly comparison between quantum physics and a programming language but the same goes for the Rust book. Rust is a hard language with sophisticated ideas. Despite the best intentions of the nice people at Mozilla, no amount of dumbing down changes that. And patronizing readers does not make the resource more approachable to women and under-represented minorities, unless you believe that those groups need to be patronized. > The set of curly brackets, {}, is a placeholder: think of {} as little crab pincers that hold a value in place.

newswasboring 6y ago
> And patronizing readers does not make the resource more approachable to women and under-represented minorities, unless you believe that those groups need to be patronized. That came out of the blue. Am I missing something? Did mozilla make such an attempt to patronize minorities?
- steveklabnik 6y ago
  I think your parent is suggesting that this whimsical example is patronizing. Some fun history here: Ruby uses #{} for string interpolation. I used to teach Ruby to folks as a job, and I believe that my boss, Jeff Casimir, said that they looked like lobster pincers in one of our classes. (If Jeff reads this and that's incorrect, my apologies!) Years later, when I was writing this part of the book, I remembered this analogy, and we had the whole crab thing going on with Rust, and I thought it was a fun thing. So I put it in the book. Some people find whimsy inherently patronizing or something. I dunno. It's an offhanded fun comment, not some sort of desire to "dumb things down" for anyone. We don't write anything with the intention of dumbing things down.

boromi 6y ago

Anyone else find the navigation tricky? I wanted to flip through the book to find out the breadth of topics.

swebs 6y ago

>At least in popular media accounts, a very common description is that a state like 0.6∣0⟩ + 0.8∣1⟩ is “simultaneously” in the ∣0⟩ state and the ∣1⟩ state. >I must confess, I don’t understand what people mean by this. I think they're just trying to tie it to Schrödinger's cat somehow since that's the only other topic that seems to be covered in pop science.

Q_is_4_Quantum 6y ago

Note its not strictly-speaking necessary to learn any linear algebra to "understand" quantum computing, there is a very simple but universal set of string-rewriting rules. I realise for this audience most people wouldn't get much from it, but I find these rules useful for explaining quantum theory without annoying and fluffy analogies to high school students. You can find the rules in my book _Q is for Quantum_ - Part I which covers quantum computing is a free download on the book website (and the rest will be if I ever get around to producing a corrected pdf, bleh, but if you read part I and don't want to pay for the rest let me know and I'll get it to you...)

gus_massa 6y ago
Are you sure the easy rewriting rules are not just 2x2 matrix multiplication?
- abdullahkhalids 6y ago
  I looked at the book and it is. His way is perhaps useful for not scaring off amateurs from learning quantum theories, but ultimately he is tricking them into learning a part of linear algebra without a foundation upon which more complex concepts can be built.
  - magsnus 6y ago
    I hate people that trick others in to learning stuff. :) This book really looks nice and short to me and I really wish the other parts comes online to.
  - Q_is_4_Quantum 6y ago
    Actually its not quite that simple. The approaches are "equivalent" (in terms of operational/statistical predictions) but not "isomorphic" (even if we restrict the regular linear algebra approach to the same gates as I use in the book). Basically (because of not implementing normalization/unitarity) in certain situations the "mist" retains a count of the number of "Feynman paths" that led to the output state. For example, concatenate two PETE boxes (hadamard gates) and the output is [W,W], concatenate four and its [W,W,W,W]. Operationally identical (you only observe the ball to be certainly white!) and applying a suitable simplification rule you "drop the extras" of course. But if someone (unlike me!) wants to think of these states as having ontological status maybe they would think the distinction is relevant. A much more interesting example of something similar happens in the Deutch-Hayden version of Heisenberg picture style quantum theory. There from looking at the "state of the world" you can determine which total unitary evolution occurred to get you there. In the Schroedinger picture, if I give you the inital and final states there are many possible unitaries that get you between them. Its possible to go further and come up with versions where not only the total unitary connecting initial and final state is discernable, but also the sequence of Hamiltonian's that implemented it are too. These things are mainly of interest to people in foundations of course (since they like to play the game of blurring the line between our math and what is "really out there"). I tried to be very careful in the book to maintain the distinction.

kensavage 6y ago

I thought quantum computing was something of science fiction? I still can’t wrap my head around it so as far as I’m concerned it’s hullabaloo.

zeepzeep 6y ago

Are other intros not free?!