Set of all decision problems solvable by a Turing machine, i.e. that decide if a string belongs to a recursive language.

Is a decision problem of determining if something belongs to a non-recursive language.

Or in other words: there is no Turing machine that always halts for every input with the yes/no output.

Every undecidable problem must obviously have an infinite number of "possibilities of stuff you can try": if there is only a finite number, then you can brute-force it.

Some undecidable problems are of recursively enumerable language, e.g. the halting problem.

Lists of undecidable problems.

Coolest ones besides the obvious boring halting problem:

Same as recursive language but in the context of the integers.

Ciro Santilli supports full legalization of all drugs, because he feels that it would be better overall for the world to have cheaper drugs and more drug addicts, but way, way less organized crime.

These should be extremely controlled of course, with extremely high taxes that puts their price just below the current illegal market, and a complete ban on any positive advertising.

Ciro believes that maybe the government could even go as far as giving free drugs to drug addicts so they don't have to rob to get a fix.

This is notably considering that drug-led organized crime completely dominates and corrupts the politics of many production and trafficking zones, which are already generally poor fucked up places to start with:Ciro's experiences in Brazil such as mentioned at São Remo, the favela next to USP, although much less extreme than the above, also come to mind.

Drug traffic corrupts everything. It prevents development of honest people. It is a cancer, which we have failed time and time a gain to cure. The only cure is to accept the other less insidious of addiction.

Bibliography:

As well put by Wikipedia, a radio receiver has to perform three functions on the signal from the antenna:

TODO synonym to analog quantum computer?

It is also possible to carry out quantum computing without qubits using processes with a continuous spectrum of measurement.

As of 2020, these approaches seem less developed/promising, but who knows.

These computers can be seen as analogous to classical non-quantum analog computers.

Similar to quantum supremacy, but add the goal that the computation must be useful, i.e. make money or solve some open mathematical problem, Ciro Santilli's wife was quite excited about the possibility of finding some counter examples in number theory with quantum computers.

One of the four following states:

When unqualified as in "the Bell state", it generally just means $|{\Phi }^{+}⟩$.

The Bell states are entangled and non-separable. Intuitively, we can see that when we measure that state, the values of the first and second bit are strictly correlated. This is the hallmark of quantum computation: making up states where qubits are highly correlated to match a specific algorithmic answer, and opposed to uniformly random noise. For example, the Bell state circuit is a common hello world, e.g. it is used in the official Qiskit hello world.