Quantum Intermediate Representation Updated 2025-07-16
Presumably the point of it is to allow simulation in classical computers?
Cavendish Laboratory Updated 2025-07-16
Cayley-Dickson construction Updated 2025-07-16
Constructs the quaternions from complex numbers, octonions from quaternions, and keeps doubling like this indefinitely.
Cheap robot Updated 2025-07-16
Quantum key distribution Updated 2025-07-16
Man-in-the-middle attack
quantumcomputing.stackexchange.com/questions/142/advantage-of-quantum-key-distribution-over-post-quantum-cryptography/25727#25727 Advantage of quantum key distribution over post-quantum cryptography has Ciro Santilli's comparison to classical encryption.
Long story short:
- QKD allows you to generate shared keys without public-key cryptography. You can then use thses shared keys
- QKD requires authentication on a classical channel, exactly like a classical public-key cryptography forward secrecy would. The simplest way to do this is a with a pre-shared key, just like in classical public key cryptography. If that key is compromised at any point, your future messages can get man-in-the-middle'd, exactly like in classical cryptography.
QKD uses quantum mechanics stuff to allow sharing unsnoopable keys: you can detect any snooping and abort communication. Unsnoopability is guaranteed by the known laws of physics, up only to engineering imperfections.
Furthermore, it allows this key distribution without having to physically take a box by car somewhere: once the channel is established, e.g. optical fiber, you can just keep generating perfect keys from it. Otherwise it would be pointless, as you could just drive your one-time pad key every time.
However, the keys likely have a limited rate of generation, so you can't just one-time pad the entire message, except for small text messages. What you would then do is to use the shared key with symmetric encryption.
Therefore, this setup usually ultimately relies on the idea that we believe that symmetric encryption is safer than , even though there aren't mathematical safety proofs of either as of 2020.
Quantum mechanics Updated 2025-07-16
Quantum mechanics is quite a broad term. Perhaps it is best to start approaching it from the division into:
- non-relativistic quantum mechanics: obviously the simpler one, and where you should start
- relativistic quantum mechanics: more advanced, and arguably "less useful"
Key experiments that could not work without quantum mechanics: Section "Quantum mechanics experiment".
Mathematics: there are a few models of increasing precision which could all be called "quantum mechanics":
Ciro Santilli feels that the largest technological revolutions since the 1950's have been quantum related, and will continue to be for a while, from deeper understanding of chemistry and materials to quantum computing, understanding and controlling quantum systems is where the most interesting frontier of technology lies.
Chicago Updated 2025-07-16
Chorus effect Updated 2025-07-16
Atomic and laser Physics subdepartment of the University of Oxford Updated 2025-07-16
Knol Updated 2025-07-16
Very similar to OurBigBook.com!
People who worked on it:
- Udi Manber: project lead
- www.wired.com/2008/07/google-knol/ mentions various engineers. The original page had photos, including the full team photo, but these died, but are visible on the archive: web.archive.org/web/20151220002650/http://www.wired.com/2008/07/google-knol/.
- Ben McMahan: "Developed, launched, and maintained Knol", mentioned at:
- x.com/benjmcmahan
- www.benjaminmcmahan.com/ has email
ben.j.mcmahan@gmail.com
- Michael McNally (2007-2009), "project's technical lead": mentioned at: www.wired.com/2008/07/google-knol/,
- github.com/xiangtiandai Xiangtian Dai
xiangtian.dai@google.com - Mohsin Ahmed: can't find any online profiles
Replying to a listener phone-in question WNYC radio, mediated by Brian Lehrer.
It was about to launch it seems, and it was not clear at the time that anyone could write content, as opposed to only selected people.
It was about to launch it seems, and it was not clear at the time that anyone could write content, as opposed to only selected people.
Jimmy then corrects that misinformation. He then clearly states that since there can be multiple versions of each article, including opinion pieces, like OurBigBook.com, Knol would be very different to Wikipedia, more like blogging than encyclopedia.
Google Knol: the future of academic journals? by Doug Belshaw (2010)
Source. Bibliography:
- Wikipedia & Knol: Why Knol Already Failed by gwern.net (2009). So there was some kind of monetary payment on the site. Interesting and sad.
Lab vs cyclotron X-ray crystallography Updated 2025-07-16
cyclotrons produce the better images, but they are expensive/you have to move to them and order a timeslot.
Lab-based just use some X-ray source from the lab, so it is much move convenient e.g. for a pharmaceutical company doing a bunch of images. The Wikipedia image shows such a self-contained lab system: en.wikipedia.org/wiki/File:Freezed_XRD.jpg
Atomic clock Updated 2025-07-16
How an atomic clock works, and its use in the global positioning system (GPS) by EngineerGuy (2012)
Source. Shows how conceptually an atomic clock is based on a feedback loop of two hyperfine structure states of caesium atoms (non-radioactive caesium-133 as clarified by the Wikipedia page). Like a quartz clock, it also relies on the piezoelectricity of quartz, but unlike the quartz clock, the quartz is not shaped like a tuning fork, and has a much larger resonating frequency of about 7 MHz. The feedback is completed by producing photons that resonate at the right frequency to excite the caesium.Inside the HP 5061A Cesium Clock by CuriousMarc (2020)
Source. A similar model was used in the Hafele-Keating experiment to test special relativity on two planes flying in opposite directions. Miniaturization was key.
Contains a disposable tube with 6g of Caesium. You boil it, so when it runs out, you change the tube, 40k USD. Their tube is made by Agilent Technologies, so a replacement since that opened in 1999, and the original machine is from the 60s.
Detection is done with an electron multiplier.
youtu.be/eOti3kKWX-c?t=1166 They compare it with their 100 dollar GPS disciplined oscillator, since GPS satellites have atomic clocks in them.
Quick presentation of the atomic clock at the National Physical Laboratory (2010)
Source. Their super accurate setup first does laser cooling on the caesium atoms. Atomic orbital Updated 2025-07-16
In the case of the Schrödinger equation solution for the hydrogen atom, each orbital is one eigenvector of the solution.
Remember from time-independent Schrödinger equation that the final solution is just the weighted sum of the eigenvector decomposition of the initial state, analogously to solving partial differential equations with the Fourier series.
This is the table that you should have in mind to visualize them: en.wikipedia.org/w/index.php?title=Atomic_orbital&oldid=1022865014#Orbitals_table
Audio editor Updated 2025-07-16
Aum Shinrikyo Updated 2025-07-16
Australia Updated 2025-07-16
Authentic learning Updated 2025-07-16
Author Updated 2025-07-16
Autothrophs and heterothrophs Updated 2025-07-16
Average length of a Snakes and Ladders game Updated 2025-07-16
Since Snakes and Ladders is nothing but a Absorbing Markov chain, the results are exactly the same as for that general problem.
www.jstor.org/stable/3619261: How Long Is a Game of Snakes and Ladders? by Althoen, King and Schilling (1993), paywalled.
There are unlisted articles, also show them or only show them.