Topics (203k) Articles (205k) Users (298) Discussions (237) Comments (383) Files (715) New article
Controlled quantum gates are gates that have two types of input qubits:These gates can be understood as doing a certain unitary operation only if the control qubits are enabled or disabled.
- control qubits
- operand qubits (terminology made up by Ciro Santilli just now)
Generic controlled quantum gate symbol
. Source. When the operand has a conventional symbol, e.g. the Figure "Quantum NOT gate symbol" for the quantum NOT gate to form the CNOT gate, that symbol is used in the operand instead.
The most common way to construct multi-qubit gates is to use single-qubit gates as part of a controlled quantum gate.
The quantum NOT gate swaps the state of and , i.e. it maps:As a result, this gate also inverts the probability of measuring 0 or 1, e.g.
- if the old probability of 0 was 0, then it becomes 1
- if the old probability of 0 was 0.2, then it becomes 0.8
The Hadamard gate takes or (quantum states with probability 1.0 of measuring either 0 or 1), and produces states that have equal probability of 0 or 1.
The first two that you should study are:
List of handbooks open as of 2022 at: www.maths.ox.ac.uk/members/students/undergraduate-courses/teaching-and-learning/handbooks-synopses Kudos, e.g. unlike the physics course of the University of Oxford which paywalled them. 2022 one: www.maths.ox.ac.uk/system/files/attachments/UG%20Handbook%202022.pdf
The Oxford mathematics Moodle has detailed course listings, and most PDFs are not paywalled.
E.g. the 2024 course:
- Year 1: everything seems mandatory:
- Michaelmas Term
- Introduction to University Mathematics
- Introduction to Complex Numbers
- Linear Algebra I
- Analysis I
- Introductory Calculus
- Probability
- Geometry
- Hilary Term
- Trinity Term
- Groups and Group Actions
- Analysis III
- Statistics and Data Analysis
- Constructive Mathematics
- Michaelmas Term
- Year 2:
- Mandatory big courses:
- long options:
- Rings and Modules
- Integration
- Topology
- Differential Equations 2
- Numerical Analysis
- Probability
- Statistics
- Fluids and Waves
- Quantum Theory
- short options
- Number Theory
- Group Theory
- Projective Geometry
- Integral Transforms
- Calculus of Variations
- Graph Theory
- Mathematical Modelling in Biology
- Year 3: pick any 8 courses. Does not say which courses exist in PDF but we can get them from courses.maths.ox.ac.uk/course/index.php?categoryid=814 of the Oxford mathematics Moodle:
- Michaelmas
- B1.1 Logic (2024-25)
- B2.1 Introduction to Representation Theory (2024-25)
- B3.2 Geometry of Surfaces (2024-25)
- B3.5 Topology and Groups (2024-25)
- B4.1 Functional Analysis I (2024-25)
- B5.2 Applied Partial Differential Equations (2024-25)
- B5.3 Viscous Flow (2024-25)
- B5.5 Further Mathematical Biology (2024-25)
- B6.1 Numerical Solution of Partial Differential Equations (2024-25)
- B6.3 Integer Programming (2024-25)
- B7.1 Classical Mechanics (2024-25)
- B8.1 Probability, Measure and Martingales (2024-25)
- B8.4 Information Theory (2024-25)
- B8.5 Graph Theory (2024-25)
- BO1.1 History of Mathematics (2024-25)
- BOE Other Mathematical Extended Essay (2024-25)
- BSP Structured Projects (2024-25)
- Hilary
- B1.2 Set Theory (2024-25)
- B2.2 Commutative Algebra (2024-25)
- B2.3 Lie Algebras (2024-25)
- B3.1 Galois Theory (2024-25)
- B3.3 Algebraic Curves (2024-25)
- B3.4 Algebraic Number Theory (2024-25)
- B4.3 Distribution Theory (2024-25)
- B4.2 Functional Analysis II (2024-25)
- B5.1 Stochastic Modelling of Biological Processes (2024-25)
- B5.4 Waves and Compressible Flow (2024-25)
- B5.6 Nonlinear Dynamics, Bifurcations and Chaos (2024-25)
- B6.2 Optimisation for Data Science (2024-25)
- B7.2 Electromagnetism (2024-25)
- B7.3 Further Quantum Theory (2024-25)
- B8.2 Continuous Martingales and Stochastic Calculus (2024-25)
- B8.3 Mathematical Models of Financial Derivatives (2024-25)
- B8.6 High Dimensional Probability (2024-25)
- SB3.1 Applied Probability (2024-25)
- BO1.1 History of Mathematics (2024-25)
- BOE Other Mathematical Extended Essay (2024-25)
- BSP Structured Projects (2024-25)
- Michaelmas
- Year 4: pick any 8 courses (up to 10 if you're crazy). Does not say which courses exist in PDF but we can get them from courses.maths.ox.ac.uk/course/index.php?categoryid=814 of the Oxford mathematics Moodle:
- Michaelmas
- C1.1 Model Theory (2024-25)
- C1.4 Axiomatic Set Theory (2024-25)
- C2.2 Homological Algebra (2024-25)
- C2.4 Infinite Groups (2024-25)
- C2.7 Category Theory (2024-25)
- C3.1 Algebraic Topology (2024-25)
- C3.3 Differentiable Manifolds (2024-25)
- C3.4 Algebraic Geometry (2024-25)
- C3.7 Elliptic Curves (2024-25)
- C3.8 Analytic Number Theory (2024-25)
- C4.1 Further Functional Analysis (2024-25)
- C4.3 Functional Analytic Methods for PDEs (2024-25)
- C5.2 Elasticity and Plasticity (2024-25)
- C5.5 Perturbation Methods (2024-25)
- C5.7 Topics in Fluid Mechanics (2024-25)
- C5.11 Mathematical Geoscience (2024-25)
- C5.12 Mathematical Physiology (2024-25)
- C6.1 Numerical Linear Algebra (2024-25)
- C6.5 Theories of Deep Learning (2024-25)
- C7.1 Theoretical Physics (C6) (2024-25)
- C7.5 General Relativity I (2024-25)
- C8.1 Stochastic Differential Equations (2024-25)
- C8.3 Combinatorics (2024-25)
- CCD Dissertations on a Mathematical Topic (2024-25)
- COD Dissertations on the History of Mathematics (2024-25)
- Hilary
- C1.2 Gödel's Incompleteness Theorems (2024-25)
- C1.3 Analytic Topology (2024-25)
- C2.3 Representation Theory of Semisimple Lie Algebras (2024-25)
- C2.5 Non-Commutative Rings (2024-25)
- C2.6 Introduction to Schemes (2024-25)
- C3.2 Geometric Group Theory (2024-25)
- C3.5 Lie Groups (2024-25)
- C3.6 Modular Forms (2024-25)
- C3.9 Computational Algebraic Topology (2024-25)
- C3.10 Additive Combinatorics (2024-25)
- C3.11 Riemannian Geometry (2024-25)
- C3.12 Low-Dimensional Topology and Knot Theory (2024-25)
- C4.6 Fixed Point Methods for Nonlinear PDEs (2024-25)
- C4.9 Optimal Transport & Partial Differential Equations (2024-25)
- C5.1 Solid Mechanics (2024-25)
- C5.4 Networks (2024-25)
- C5.6 Applied Complex Variables (2024-25)
- C6.2 Continuous Optimisation (2024-25)
- C6.4 Finite Element Method for PDEs (2024-25)
- C7.1 Theoretical Physics (C6) (2024-25)
- C7.4 Introduction to Quantum Information (2024-25)
- C7.6 General Relativity II (2024-25)
- C7.7 Random Matrix Theory (2024-25)
- C8.2 Stochastic Analysis and PDEs (2024-25)
- C8.4 Probabilistic Combinatorics (2024-25)
- C8.7 Optimal Control (2024-25)
- CCD Dissertations on a Mathematical Topic (2024-25)
- COD Dissertations on the History of Mathematics (2024-25)
- Michaelmas
Aptitude test scene from the Snowden 2016 film
. Source. FISA Court Order The Guardian discussion scene from the Snowden 2016 film
. Source. How is this Possible? scene from the Snowden 2016 film
. Source. Fresh Brains for You scene from the Snowden 2016 film
. Source. The last value we will likely every know for the busy beaver function! BB(6) is likely completely out of reach forever.
By 2023, it had basically been decided by the The Busy Beaver Challenge as mentioned at: discuss.bbchallenge.org/t/the-30-to-34-ctl-holdouts-from-bb-5/141, pending only further verification. It is going to be one of those highly computational proofs that will be needed to be formally verified for people to finally settle.
As that project beautifully puts it, as of 2023 prior to full resolution, this can be considered the:on the Busy beaver scale.
simplest open problem in mathematics
Quantum Computation and Quantum Information by Nielsen and Chuang by 
Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16Lists of the most promising implementations:
As of 2020, the hottest by far are:
Super quick overview of the main types of quantum computer physical implementations, so doesn't any much to a quick Google.
He says he's going to make a series about it, so then something useful might actually come out. The first one was: Video "How to Turn Superconductors Into A Quantum Computer by Lukas's Lab (2023)", but it is still too basic.
The author's full name is Lukas Baker, www.linkedin.com/in/lukasbaker1331/, found with Google reverse image search, even though the LinkedIn image is very slightly different from the YouTube one.
To get an intuition for it, see the sample computation at: en.wikipedia.org/w/index.php?title=Ackermann_function&oldid=1170238965#TRS,_based_on_2-ary_function where in this context. From this, we immediately get the intuition that these functions are recursive somehow.
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!
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-calculusArticles 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/derivativeVideo 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: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.
- 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
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 5. . 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. 
- Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact