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Ciro Santilli  40 Updated 2025-07-16

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Bibliography:

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Handscroll by

Ciro Santilli  40 Updated 2025-07-16

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Ciro Santilli's favorite. A mixture of painting and book.

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Champaign-Urbana metropolitan area by

Ciro Santilli  40 Updated 2025-07-16

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It is quite comical that two separate towns were founded one next to the other right in the middle of nowhere. And that both have so slightly weird names.

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Bilibili by

Ciro Santilli  40 Updated 2025-07-16

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B4 Oxford physics course by

Ciro Santilli  40 Updated 2025-07-16

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www-pnp.physics.ox.ac.uk/~barra/teaching.shtml As of 2023, contains some good 2015 materials: web.archive.org/web/20220525094139/http://www-pnp.physics.ox.ac.uk/~barra/teaching.shtml It was called "Subatomic physics" back then.

2015 professor: Alan J. Barr.

Possible 2022 professor: Guy Wilkinson (unconfirmed): www.chch.ox.ac.uk/staff/professor-guy-wilkinson

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B2 Oxford physics course by

Ciro Santilli  40 Updated 2025-07-16

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www-thphys.physics.ox.ac.uk/people/AndreiStarinets/sr_mt_2022.html (archive) contains 2022 problem sets and notes, well done Mr Andrei Starinets!

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Quantum Software course of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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2022 page: www.cs.ox.ac.uk/teaching/courses/qsoft/ Half of the problems are Jupyter Notebooks, not bad.

Like Quantum Processes and Computation course of the University of Oxford, also ZX-calculus-heavy.

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Quantum Processes and Computation course of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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2022 page: www.cs.ox.ac.uk/teaching/courses/2022-2023/quantum/ (archive). Assignments are available:

2022 lecturer: Aleks Kissinger

The course would be better named ZX-calculus as it appears to be the only subject covered.

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Tensor product in quantum computing by

Ciro Santilli  40 Updated 2025-07-16

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We don't need to understand a super generalized version of tensor products to know what they mean in basic quantum computing!

Intuitively, taking a tensor product of two qubits simply means putting them together on the same quantum system/computer.

When we write the bra-ket notation:

∣ 00 ⟩

that is the same as

∣ 0 ⟩ \otimes ∣ 0 ⟩

The tensor product is called a "product" because it distributes over addition.

E.g. consider:

(\frac{∣ 0 ⟩ + ∣ 1 ⟩}{2}) \otimes ∣ 0 ⟩ = \frac{∣ 0 ⟩ \otimes ∣ 0 ⟩ + ∣ 1 ⟩ \otimes ∣ 0 ⟩}{2} = \frac{∣ 00 ⟩ + ∣ 10 ⟩}{2}

(1)

Intuitively, in this operation we just put a Hadamard gate qubit together with a second pure

∣ 0 ⟩

qubit.

And the outcome still has the second qubit as always 0, because we haven't made them interact.

The quantum state

\frac{∣ 00 ⟩ + ∣ 10 ⟩}{2}

is called a separable state, because it can be written as a single product of two different qubits. We have simply brought two qubits together, without making them interact.

If we then add a CNOT gate to make a Bell state:

\frac{∣ 00 ⟩ + ∣ 11 ⟩}{2} = \frac{∣ 0 ⟩ \otimes ∣ 0 ⟩ + ∣ 1 ⟩ \otimes ∣ 1 ⟩}{2}

(2)

we can now see that the Bell state is non-separable: we've made the two qubits interact, and there is no way to write this state with a single tensor product. The qubits are fundamentally entangled.

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Quantum state vector by

Ciro Santilli  40 Updated 2025-07-16

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numpy/fft.py by

Ciro Santilli  40 Updated 2026-09-20

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Output:

sin(t)
fft
real 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
imag 0 -10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 10
rfft
real 0 0 0 0 0 0 0 0 0 0 0
imag 0 -10 0 0 0 0 0 0 0 0 0

sin(t) + sin(4t)
fft
real 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
imag 0 -10 0 0 -10 0 0 0 0 0 0 0 0 0 0 0 10 0 0 10
rfft
real 0 0 0 0 0 0 0 0 0 0 0
imag 0 -10 0 0 -10 0 0 0 0 0 0

With our understanding of the discrete Fourier transform we see clearly that:

the signal is being decomposed into sinusoidal components
because we are doing the Discrete Fourier transform of a real signal, for the fft, $X_{k} = \overset{ˉ}{X_{N - k}}$ so there is redundancy in the. We also understand that rfft simply cuts off and only keeps half of the coefficients

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Department of Computer Science of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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www.cs.ox.ac.uk

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Year 4 of the computer science course of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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Quantum Information course of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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www.cs.ox.ac.uk/teaching/courses/qi/

2023: Jonathan Barrett

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Year 2 or 3 course of the computer science course of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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Busy Beaver Challenge by

Ciro Santilli  40 Updated 2025-07-16

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bbchallenge.org/story

Project trying to compute BB(5) once and for all. Notably it has better presentation and organization than any other previous effort, and appears to have grouped everyone who cares about the topic as of the early 2020s.

Very cool initiative!

By 2023, they had basically decided every machine: discuss.bbchallenge.org/t/the-30-to-34-ctl-holdouts-from-bb-5/141

In June 2024 they felt that they had verified the result after a full Coq proof was published:

So now onto BB(6) I guess.

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Computer science course of the University of Oxford by

Ciro Santilli  40 Updated 2025-07-16

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Public landing page: www.ox.ac.uk/admissions/undergraduate/courses/course-listing/computer-science

Course lists: www.cs.ox.ac.uk/teaching/courses/ True to form, courses appear to have identifiers, e.g. qi for the Quantum Information course of the University of Oxford rather than more arbitrary A1/A2/A3, B1/B2/B3, naming convention used by the Mathematics course of the University of Oxford and the Physics course of the University of Oxford, and URLs can either have years or not:

www.cs.ox.ac.uk/teaching/courses/qi/: no year: goes to latest
www.cs.ox.ac.uk/teaching/courses/2023-2024/qi/: has year, fixed year. Disgraceful repetition of redundant 2023-2024, but OK.

The "course materials" section of each course leads to courses.cs.ox.ac.uk/ which is paywalled by IP (accessible via Eduroam): TODO which system does it use? Some courses place their materials directly on "www.cs.ox.ac.uk", and when that is the case they are publicly accessible. So it is very much hit and miss. E.g. www.cs.ox.ac.uk/teaching/courses/2022-2023/quantum/index.html from Quantum Processes and Computation course of the University of Oxford has the assignments such as www.cs.ox.ac.uk/people/aleks.kissinger/courses/qpc2022/assignment1.pdf publicly visible, but e.g. www.cs.ox.ac.uk/teaching/courses/2022-2023/modelsofcomputation/ has nothing.

Handbook:

2022:
- general www.cs.ox.ac.uk/files/13731/CS%20Handbook%20final.pdf
- Year 1 (Prelims): www.cs.ox.ac.uk/files/13794/Handbook%202022%20Part%20C%20-%20V1.3.pdf
- Year 2/3 (Parts A/B): www.cs.ox.ac.uk/files/13793/Handbook%202022%20Parts%20A%20&%20B%20V1.3.pdf There is some mixture on which courses can be taken on year 2 or 3. This also implies that they cannot have the usual A2/B2 naming scheme. They just don't have names instead mostly. It is also the most beautiful illustration of why you shouldn't do Compute Science at university: there's no depth to the subject. You can just take random courses and you learn it all quickly. Section "The only reason for universities to exist should be the laboratories".
  - Year 2 has four mandatory core courses:
    Models of Computation
    Algorithms and Data Structures
    Compilers (mandatory for compsi, but not mathematics and computer science)
    Concurrent programming
    A only:
    Probability
  - Hilary term
    Concurrent Programming (mandatory for compsi, but not mathematics and computer science)
    Quantum information
- Year 4 (Part C): www.cs.ox.ac.uk/files/13794/Handbook%202022%20Part%20C%20-%20V1.3.pdf
  - Michaelmas term
    Bayesian Statistical Probabilistic Programming
    Concurrent Algorithms and Data Structures
    Quantum Processes and Computation
    Computational Learning Theory
    Computational Biology
    Advanced Complexity Theory
    Graph Representation Learning
  - Hilary term
    Advanced Security
    Database Systems Implementation
    Ethical Computing in Practice
    Law and Computer Science
    Quantum Software course of the University of Oxford
    Geometric Deep Learning
    Foundations of Self-Programming Agents
    Deep Learning in Healthcare

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qiskit/hello.py by

Ciro Santilli  40 Updated 2025-07-16

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Our example uses a Bell state circuit to illustrate all the fundamental Qiskit basics.

Sample program output, counts are randomized each time.

First we take the quantum state vector immediately after the

∣ 00 ⟩

input.

input:
state:
Statevector([1.+0.j, 0.+0.j, 0.+0.j, 0.+0.j],
            dims=(2, 2))
probs:
[1. 0. 0. 0.]

We understand that the first element of Statevector is

∣ 00 ⟩

, and has probability of 1.0.

Next we take the state after a Hadamard gate on the first qubit:

h:
state:
Statevector([0.70710678+0.j, 0.70710678+0.j, 0.        +0.j,
             0.        +0.j],
            dims=(2, 2))
probs:
[0.5 0.5 0.  0. ]

We now understand that the second element of the Statevector is

∣ 01 ⟩

, and now we have a 50/50 propabability split for the first bit.

Then we apply the CNOT gate:

cx:
state:
Statevector([0.70710678+0.j, 0.        +0.j, 0.        +0.j,
             0.70710678+0.j],
            dims=(2, 2))
probs:
[0.5 0.  0.  0.5]

which leaves us with the final

\frac{∣ 00 ⟩ + ∣ 11 ⟩}{2}

Then we print the circuit a bit:

qc without measure:
     ┌───┐
q_0: ┤ H ├──■──
     └───┘┌─┴─┐
q_1: ─────┤ X ├
          └───┘
c: 2/══════════

qc with measure:
     ┌───┐     ┌─┐
q_0: ┤ H ├──■──┤M├───
     └───┘┌─┴─┐└╥┘┌─┐
q_1: ─────┤ X ├─╫─┤M├
          └───┘ ║ └╥┘
c: 2/═══════════╩══╩═
                0  1
qasm:
OPENQASM 2.0;
include "qelib1.inc";
qreg q[2];
creg c[2];
h q[0];
cx q[0],q[1];
measure q[0] -> c[0];
measure q[1] -> c[1];

And finally we compile the circuit and do some sample measurements:

qct:
     ┌───┐     ┌─┐
q_0: ┤ H ├──■──┤M├───
     └───┘┌─┴─┐└╥┘┌─┐
q_1: ─────┤ X ├─╫─┤M├
          └───┘ ║ └╥┘
c: 2/═══════════╩══╩═
                0  1
counts={'11': 484, '00': 516}
counts={'11': 493, '00': 507}

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Qiskit Aer by

Ciro Santilli  40 Updated 2025-07-16

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github.com/Qiskit/qiskit-aer

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Qiskit hello world by

Ciro Santilli  40 Updated 2025-07-16

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The official hello world is documented at: qiskit.org/documentation/intro_tutorial1.html and contains a Bell state circuit.

Our version at qiskit/hello.py.

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 Pinned article: Introduction to the OurBigBook Project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.

Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!

Video 1.

Intro to OurBigBook

. Source.

We have two killer features:

topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
Articles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1.
Screenshot of the "Derivative" topic page
. View it live at: ourbigbook.com/go/topic/derivative
Video 2.
OurBigBook Web topics demo
. Source.
local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
Figure 2.
You can publish local OurBigBook lightweight markup files to either OurBigBook.com or as a static website
.
Figure 3.
Visual Studio Code extension installation
.
Figure 4.
Visual Studio Code extension tree navigation
.
Figure 5.
Web editor
. You can also edit articles on the Web editor without installing anything locally.
Video 3.
Edit locally and publish demo
. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
Video 4.
OurBigBook Visual Studio Code extension editing and navigation demo
. Source.
Internal cross file references done right:
Infinitely deep tables of contents:
Figure 6.
Dynamic article tree with infinitely deep table of contents
.
Live URL: ourbigbook.com/cirosantilli/chordate
Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade