Recent content by JK423

But as AlexCaledin pointed out, the particles don't have to be separated to be described by an entangled quantum state.

Indeed, sepatedness is not fundamental to entanglement per se. However we do use it in the argument in order to demonstrate clearly and beyond doubt how "paradoxical" entanglement is. If the systems are not separated, and therefore not independent from each other, it's not clear what's so...

I think a rigorous way to define, and consequently interpret, entanglement is the following: Given two separated and non-interacting quantum systems A and B, they are said to be entangled if and only if we cannot assign a definite quantum state to each system ( ##\sigma^k_A## and ##w^k_B##...

That makes sense! Thanks a lot

As we all know, the LIGO collaboration published a paper recently on the first direct observation of a binary merging black hole system. From the observed signal, they were able to infer the black holes' masses and their distance from Earth. However, the fact that they can estimate masses and...

Maybe you should change your notion of 'classical' computer, and your problem is solved. Classical computers, defined as computers that do not take advantage of genuine quantum effects in the computation, are still constrained by the laws of physics when it comes to how fast a computation can be...

Short answer: nobody knows yet! It's a really interesting question. People are trying to find what the minimal quantum resources are (like; entanglement, contextuality, discord, etc) such that the quantum algorithm will still give advantage over classical computing. The usual algorithms, like...

Not really. I mean, Bell inequalities are being violated routinely these days. (Almost) Nobody believes that if all loopholes are closed the experimental outcome will be different, everybody still expects to see the same Bell violation. If we did close all the loopholes, and we saw to our...

In the quest of searching what are the basic ingredients of quantum theory that provide exponential speed-up to some quantum algorithms, a basic question that is pursued in the literature is when a quantum circuit (or algorithm) can be classically simulated efficiently. One example is this paper...

TrickyDicky and PeterDonis are you still disagreeing on the reality of virtual particles or on the definions of off/on shell?

@Gerinski: Yes, that assertion is wrong. And you will not find it in any 'good' textbook on QFT. The reason why quantum tunneling happens is because the particle that tunnels does not have a well defined energy beforehand, i.e. it is in a superposition of states with different energies...

The question of the reality of virtual particles arise a looot of times in a number of threads, and of course the reason is the usual treatment by textbooks. People mean different things with the word *virtual*. Some mean the artifacts of perturbation theory, others mean the on/off shell...

Let me try to defend the title and the authors a bit. The words "nonlocal wavefunction collapse" describe the words and position of EPR and Schrödinger on the subject. They thought exactly that, Alice can collapse the state of Bob into totally different states depending on her measurement...

Why do you think that they have similar algebraic structure? First of all, the mathematical space that the two theories live in is different, and the 'states' of the particles in the two theories (quantum states for QM and position for Classical M.) are different mathematical objects that...

You cannot even say, strictly speaking, 'when' you measure something. There is a fundamental (quantum) uncertainty, and you cannot predict beforehand 100% when the outcome will appear.