Ciro Santilli @cirosantilli  40

The first quantum mechanics theories developed.

Their most popular formulation has been the Schrödinger equation.

Photon energy is proportional to its frequency:or with common weird variables:

This only makes sense if the photon exists, there is no classical analogue, because the energy of classical waves depends only on their amplitude, not frequency.

Experiments that suggest this:

The first really good quantum mechanics theory made compatible with special relativity was the Dirac equation.

And then came quantum electrodynamics to improve it: Dirac equation vs quantum electrodynamics.

TODO: does it use full blown QED, or just something intermediate?

www.youtube.com/watch?v=NtnsHtYYKf0 "Mercury and Relativity - Periodic Table of Videos" by Periodic Videos (2013). Doesn't give the key juicy details/intuition. Also mentioned on Wikipedia: en.wikipedia.org/wiki/Relativistic_quantum_chemistry#Mercury

Quantum field theory lecture by Tobias Osborne (2017) mentions that quantization is a guess.

Quantum superposition is really weird because it is fundamentally different than "either definite state but I don't know which", because the superposition state leads to different measurements than the non-superposition state.

Examples:

Quantum entanglement is often called spooky/surprising/unintuitive, but they key question is to understand why.

To understand that, you have to understand why it is fundamentally impossible for the entangled particle pair be in a predefined state according to experiments done e.g. where one is deterministically yes and the other deterministically down.

In other words, why local hidden-variable theory is not valid.

How to generate entangled particles:

Quantum is getting hot in 2019, and even Ciro Santilli got a bit excited: quantum computing could be the next big thing.

No useful algorithm has been economically accelerated by quantum yet as of 2019, only useless ones, but the bets are on, big time.

To get a feeling of this, just have a look at the insane number of startups that are already developing quantum algorithms for hardware that doesn't/barely exists! quantumcomputingreport.com/players/privatestartup (archive). Some feared we might be in a bubble: Are we in a quantum computing bubble?

To get a basic idea of what programming a quantum computer looks like start by reading: Section "Quantum computing is just matrix multiplication".

Some people have their doubts, and that is not unreasonable, it might truly not work out. We could be on the verge of an AI winter of quantum computing. But Ciro Santilli feels that it is genuinely impossible to tell as of 2020 if something will work out or not. We really just have to try it out and see. There must have been skeptics before every single next big thing.

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.

BB84 is a good first algorithm to look into.

Long story short:

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.

Best ones:

In Ciro Santilli's view, the following three artists form a Holy Trinity of popular Brazilian music:

Elis Regina is not far though.

Ciro remembers quite clearly when he was riding the car with his parents when he pre teen, and he could not understand why they seemed so obsessed with The Trinity et al. Ciro in particular remembers listening to Video "Refazenda by Gilberto Gil (1975)". They had picked it up of course from the 70's and 80's when they were younger.

Young Ciro would also always confuse who was whom from the three of them.

Then Ciro got older, and he understood, they are mind blowing. You do have to look back in time a bit though, lots of lukewarm stuff on later periods. The military dictatorship in Brazil was good for music.

Mostly interpreter of songs written by others. But she's just too amazing, many of her interpretations are better than the original.

God, even Ciro Santilli is slightly shocked by her death, which happened before he was born, can you imagine it at the time? She was MPB's golden girl...

There are no stable isotopes.

Once upon a time in the 2010's, Ciro Santilli went to an artsy theatre venue in the suburbia of Paris, dragged by his wife then girlfriend of course.

In the venue, there was a politician, who was doing his best to show how much they supported the arts, and there were of course the artists, involved in the play.

The politician would see a political power score on top of every person's head, and would spend an amount of time talking to each person exactly proportional to that score. This meant basically one sentence to us. The words themselves didn't really matter of course, only the time spent, they just have to produce nice sounds.

One of the artists however, and he seemed quite important in the production, for some reason spent a huge amount of time speaking to us. The score the artist saw on our heads was of love, or how interested we were in the art.