Quantum Information course of the University of Oxford Updated 2025-07-16
2023: Jonathan Barrett
Stack Overflow link-only answer policy Updated 2025-07-16
The link will break, and the answer will lose. Or the person who summarizes inline will get more upvotes because people are lazy to click the link. Also, web archiving exists.
This is especially idiotic when it is a link to another post in Stack Overflow itself.
Classification of simple Lie groups Updated 2025-07-16
A bit like the classification of simple finite groups, they also have a few sporadic groups! Not as spectacular since as usual continuous problems are simpler than discrete ones, but still, not bad.
ORF1ab Updated 2025-07-16
Pangaea Updated 2025-07-16
Peripheral Updated 2025-07-16
Polarization of light Updated 2025-07-16
This section discusses the pre-photon understanding of the polarization of light. For the photon one see: photon polarization.
People were a bit confused when experiments started to show that light might be polarized. How could a wave that propages through a 3D homgenous material like luminiferous aether have polarization?? Light would presumably be understood to be analogous to a sound wave in 3D medium, which cannot have polarization. This was before Maxwell's equations, in the early 19th century, so there was no way to know.
Province of China Updated 2025-07-16
Udacity Updated 2025-07-16
It is a shame that they refocused to more applied courses. This also highlights their highly "managed" approach to content creation. Their 2022 pitch on front page says it all:they are focused on the highly paid character of many software engineering jobs.
for as few as 10 hours a week, you can get the in-demand skills you need to help land a high-paying tech job
But one cool point of this website is how they hire tutors to help on the courses. This is a very good thing. It is a fair way of monetizing: e-learning websites must keep content free, only charge for certification.
x86 Paging Tutorial TLB replacement policy Updated 2025-07-16
When TLB is filled up, older addresses are overwritten. Just like CPU cache, the replacement policy is a potentially complex operation, but a simple and reasonable heuristic is to remove the least recently used entry (LRU).
With LRU, starting from state:adding
valid linear physical
----- ------ --------
> 1 00003 00005
1 00007 00009
1 00009 00001
1 0000B 000030000D -> 0000A would give: valid linear physical
----- ------ --------
1 0000D 0000A
> 1 00007 00009
1 00009 00001
1 0000B 00003 Allegory Updated 2025-07-16
Internet privacy organizations Updated 2025-07-16
Open instant messaging protocols Updated 2025-07-16
Robert Noyce Updated 2025-07-16
Superconducting magnet Updated 2025-07-16
Applications: produce high magnetic fields forAs of the early 2020s, superconducting magnets predominantly use low temperature superconductors Nb-Ti and Nb-Sn, see also most important superconductor materials, but there were efforts underway to create practical high-temperature superconductor-based magnets as well: Section "High temperature superconductor superconducting magnet".
- magnetic resonance imaging, the most important commercial application as of the early 2020s
- more researchy applications as of the early 2020s:
Wikipedia has done well for once:
The current to the coil windings is provided by a high current, very low voltage DC power supply, since in steady state the only voltage across the magnet is due to the resistance of the feeder wires. Any change to the current through the magnet must be done very slowly, first because electrically the magnet is a large inductor and an abrupt current change will result in a large voltage spike across the windings, and more importantly because fast changes in current can cause eddy currents and mechanical stresses in the windings that can precipitate a quench (see below). So the power supply is usually microprocessor-controlled, programmed to accomplish current changes gradually, in gentle ramps. It usually takes several minutes to energize or de-energize a laboratory-sized magnet.
Superconductivity: magnetic separation by University of Cambridge
. Source. Superconducting quantum computer need non-linear components Updated 2025-07-16
Non-linearity is needed otherwise the input energy would just make the state go to higher and higher energy levels, e.g. from 1 to 2. But we only want to use levels 0 and 1.
The way this is modelled in by starting from a pure LC circuit, which is an harmonic oscillator, see also quantum LC circuit, and then replacing the linear inductor with a SQUID device, e.g. mentioned at: youtu.be/eZJjQGu85Ps?t=1655 Video "Superconducting Qubits I Part 1 by Zlatko Minev (2020)".
Superconducting temperature of aluminum Updated 2025-07-16
Superconductivity is a a form of superfluidity Updated 2025-07-16
We know that superfluidity happens more easily in bosons, and so electrons joins in Cooper pairs to form bosons, making a superfluid of Cooper pairs!
Isn't that awesome!
List of instant messaging software Updated 2025-07-16
Physics World Updated 2025-07-16
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