[HN Gopher] A tutorial quantum interpreter in 150 lines of Lisp
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A tutorial quantum interpreter in 150 lines of Lisp
Author : varjag
Score : 167 points
Date : 2023-07-16 16:41 UTC (6 hours ago)
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| adamnemecek wrote:
| Recently, I have been working on some things that sometimes
| overlap with quantum computation and I have realized that the way
| all the quantum languages approach this wrong. If you are
| programming explicitly with CNOT gates, you are doing it wrong. A
| Python programmer doesn't care about logical gates, and neither
| should a quantum programmer. To that end, I'm convinced that the
| interplay between coinduction and induction, or coalgebra and
| algebra is the way forward.
| archgoon wrote:
| [dead]
| reikonomusha wrote:
| This very well may be true, in the same sense that a Python
| programmer doesn't (usually) care about assembly language. But
| at their lowest levels, quantum computers _are_ executing a
| sequence of gates, and much of the work and sophistication of a
| quantum compiler is to optimize said sequences for rapid and
| accurate execution. So while gate sequences may not be the end-
| game to the programmers of tomorrow, they 're undoubtedly a
| necessary component in any software stack.
| adamnemecek wrote:
| I never said that they weren't. It's just that most
| programming language don't deal with gates as a part of their
| API.
| taeric wrote:
| This is true, but at that point, the goal would be to have
| a higher level language above the quantum gates. And at
| that point, I'd guess the code is less educational?
|
| That is, at the end of the day, something like Shor's
| algorithm can be reduced to some math constructs we roughly
| know. The speedup comes from these only being efficient
| using quantum gates. Implementing the code using abstract
| quantum gates isn't to try and compete, but to try and
| understand the gates and how they work at a logical level.
|
| This is like learning how boolean gates work to understand
| some ideas of how computers work. The only people that
| really think in many of those terms are the CPU designers.
| Teaching the next round of the designers does so by working
| with boolean models to get there.
|
| And you are correct that we may have other quantum
| constructs someday. Just like much of what goes into a CPU
| isn't strictly OR/AND/etc. With the way gates are wired, it
| can be confusing to folks as the input signal can also be
| seen as destroyed in the circuit, but a deterministic
| signal is captured on the other side.
|
| Now, the above is all from my weak intuition here. I would
| not be shocked to find I'm wrong on parts.
| miguelmurca wrote:
| Maybe not your point, but a lot of programmers like to take
| this as "I should invent the Python of quantum computing",
| which is just about as silly as trying to approach anyone in
| 1960 and telling them they shouldn't be thinking about
| electronics at all.
| 082349872349872 wrote:
| > _the interplay between ... coalgebra and algebra_
|
| If you have not already seen it, you may be interested in
| Squiggol (to get an idea of its age, it probably had some
| indirect influence upon Python)
|
| cf Charity:
| https://prism.ucalgary.ca/server/api/core/bitstreams/756b50a...
| robbywashere_ wrote:
| "Thanks for interviewing with us today at xyz... please click on
| that link I just sent you in the chat. Today we will be doing a
| little quantum coding question. Try to speak out loud so I know
| what your thinking and your thought process."
| adamisntdead wrote:
| I wrote something similar a couple of years ago -
| https://github.com/adamisntdead/QuSimPy
|
| Happy to answer any questions people have, including on other
| simulation methods other than state vector!
| reikonomusha wrote:
| One of the aspects emphasized in TFA is being able to simulate
| gates of any dimension/number of qubits (like a 3-qubit Toffoli
| or a 5-qubit Molmer-Sorensen), instead of just 1- and 2-qubit
| gates. Have you thought about extending your simulator to
| support gates of greater than two qubits?
| adamisntdead wrote:
| I guess back when I wrote it I didn't see the need given that
| single qubit gates along with CNOT are universal and they're
| implemented. I think airing on the side of 'as few features
| as is educational' was my mentality on this.
| jramirezpr wrote:
| On the X gate, the more relevant identity regarding X being its
| own inverse is X*X=I, the other one is true for all invertible
| matrices
| frankdejonge wrote:
| You had me until Lisp.
| eggy wrote:
| I'm deciding between Common Lisp and Mojo, so maybe I will try to
| implement this in Mojo and compare. Anybody have any thoughts on
| this, since I am a mediocre Lisper and a beginning Mojo person. I
| am familiar with Numpy and I also program in APL and J.
| mighmi wrote:
| Any recommendations on a textbook to understand this kind of
| math?
| prezjordan wrote:
| Might be of use! https://quantum.country/
| reikonomusha wrote:
| One of the authors, Michael Nielson, also wrote the "bible"
| of quantum computing, as referenced in a sibling comment. The
| remains one of the most popular and cited introductory texts
| to the subject, though today there are many more options on
| the market.
| hackandthink wrote:
| Ronald de Wolf: Quantum Computing: Lecture Notes
|
| Ronald de Wolf:
|
| https://arxiv.org/abs/1907.09415
|
| David Bacon:
|
| https://courses.cs.washington.edu/courses/cse599d/06wi/
|
| Scott Aaronson:
|
| https://en.wikipedia.org/wiki/Quantum_Computing_Since_Democr...
| abdullahkhalids wrote:
| Quantum Computation and Quantum Information by Nielson and
| Chuang is the standard textbook for quantum computing. It has
| excellent background chapters on linear algebra and quantum
| mechanics, that will get you a lot of mileage.
|
| Another book that I would recommend is Introduction to
| Classical and Quantum Computing by Thomas Wong. It's recent and
| has lots of examples, including lots of code, to show how to
| work with the math.
| jksk61 wrote:
| maybe not of your interest, but if one is more from a ML
| background, there's this nice book/overview by Maria Schuld and
| Francesco Petruccione, called Machine Learning with Quantum
| Computers, which is mostly regarding variational algorithm and
| quantum kernel machine. However, the best intro material is the
| one by Nielsen and Chuang.
|
| Moreover, if you feel more comfortable by running examples
| there are qiskit, pennylane and other libraries which shares a
| lot of tutorials and notebook (and some can be run on a true
| quantum computer if you have the money or the time to wait in
| queue!)
| Strilanc wrote:
| The hardest part of implementing a quantum state vector
| simulation is understanding how the tensor product expands an
| n-qubit gate to apply to an m-qubit system. (A third of the
| linked post is dedicated to it; appropriately.)
|
| If you use a language or framework that's based on tensors to
| start with, things can be quite succinct (though you still need
| to understand the concepts). For example, in numpy, if you store
| the state vector in an array of shape (2,) * num_qubits, you can
| apply gates as one-liners using np.einsum:
| import numpy as np # Init 4-qubit system with all
| amplitude in the 0000 state. state = np.zeros(shape=(2,)
| * 4, dtype=np.complex64) state[(0,) * 4] = 1
| # Unitary matrix of Hadamard gate H = np.array([[1, 1],
| [1, -1]], dtype=np.complex64) / 2**0.5 # Apply
| Hadamard gate to third qubit of four qubit system. state
| = np.einsum('XY,abXd->abYd', H, state)
|
| Here's a post explaining what np.einsum does:
| https://obilaniu6266h16.wordpress.com/2016/02/04/einstein-su... .
| In the above einsum string 'XY,abXd->abYd' the 'XY' part is
| naming the input and output axes of the Hadamard matrix, and the
| 'abXd->abYd' part is saying to multiply the matrix into the third
| axis of the state tensor. The notation is pretty general, able to
| permute and repeat axes in order to express things like traces
| and transposes and dot products and etc.
| reikonomusha wrote:
| "einsum" in Lisp [1]. It uses S-expressions instead of strings,
| and compiles to native loops.
|
| [1] https://github.com/quil-lang/magicl/blob/master/src/high-
| lev...
| lionsdan wrote:
| (Link didn't work for me)
|
| https://github.com/quil-lang/magicl/blob/master/src/high-
| lev...
| jxf wrote:
| > The hardest part of implementing a quantum state vector
| simulation is understanding how the tensor product expands an
| n-qubit gate to apply to an m-qubit system. (A third of the
| linked post is dedicated to it; appropriately.)
|
| This feels like it could be the "git gets easier once you
| understand branches are homeomorphic endofunctors mapping
| submanifolds of a Hilbert space" of physics.
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