Breeder reactor Updated +Created
A nuclear reactor made to produce specific isotopes rather than just consume fissile material to produce electrical power. The most notably application being to produce Plutonium-239 for nuclear weapons from Uranium-238 being irradiated from Uranium-235-created fission.
Los Alamos From Below by Richard Feynman (1975) Updated +Created
Amazing talk by Richard Feynman that describes his experiences at Los Alamos National Laboratory while developing the first nuclear weapons.
  • www.youtube.com/watch?v=uY-u1qyRM5w&t=2881s describes the computing aspects. Particularly interesting is the quote about how they used the typist secretary pool to emulate the IBM machines and debug their programs before the machines had arrived. This is exactly analogous to what is done in 2020 in the semiconductor industry, where slower models are used to estimate how future algorithms will run in future hardware.
Plutonium Updated +Created
What a material:
  • only exists in trace amounts in nature,but it can be produced at kilogram scale in breeder reactors
  • it is only intentionally produced for one application, and one application only basically: nuclear weapons
Video 1. Source. Plutonium for self-respect scene from the 1987 film Edge Of Darkness
Video 2.
Burning and Extinguishing Characteristics of Plutonium Metal Fires by RobPlonski
. Source. Commented by this dude: www.linkedin.com/in/robplonski/
Plutonium-239 Updated +Created
This is the isotope that is produced for nuclear weapons by irradiating Uranium-238 with a neutron.
Plutonium-240 is a contaminant.
Plutonium-240 Updated +Created
This isotope shows up as an inevitable contaminant in Plutonium-239 for nuclear weapons, because it emits neutrons too fast and makes it harder to assemble the critical mass without fizzle.
It is the presence of this contaminant that made implosion-type fission weapon a necessity: Section "Gun-type fission weapons don't work with plutonium".
Wikipedia explains that Pu-240 is formed by Pu-239 Neutron capture:
About 62% to 73% of the time when 239Pu captures a neutron, it undergoes fission; the remainder of the time, it forms 240Pu.
so its presence is inevitable.
Quantum computers as experiments that are hard to predict outcomes Updated +Created
One possibly interesting and possibly obvious point of view, is that a quantum computer is an experimental device that executes a quantum probabilistic experiment for which the probabilities cannot be calculated theoretically efficiently by a nuclear weapon.
This is how quantum computing was originally theorized by the likes of Richard Feynman: they noticed that "Hey, here's a well formulated quantum mechanics problem, which I know the algorithm to solve (calculate the probability of outcomes), but it would take exponential time on the problem size".
The converse is then of course that if you were able to encode useful problems in such an experiment, then you have a computer that allows for exponential speedups.
This can be seen very directly by studying one specific quantum computer implementation. E.g. if you take the simplest to understand one, photonic quantum computer, you can make systems for which you need exponential time to calculate the probabilities that photons will exit through certain holes and not others.
The obvious aspect of this idea is by coming from quantum logic gates are needed because you can't compute the matrix explicitly as it grows exponentially: knowing the full explicit matrix is impossible in practice, and knowing the matrix is equivalent to knowing the probabilities of every outcome.
United States Department of Energy national laboratory Updated +Created
Where nuclear weapons and nuclear power, and a ton of derived research is made.
Weapons-grade nuclear material Updated +Created
For nuclear weapons you need a certain level of isotope purity of either plutonium-239 or uranium-235.
And the easiest way by far to achieve this purity is to produce plutonium-239 in a breeder reactor, which allows you to get it out with much cheaper chemical processes rather than costly isotope separation methods.
fissilematerials.org/ summarizes stockpiles and production status. 20224 Archive.