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Chinese Researchers Achieve Quantum Entanglement Record

scientificamerican.com

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Re: Chinese Researchers Achieve Quantum Entanglement Record

#81

Post by danbruc »

crumpington wrote: post #75
bazinga56 wrote: post #71

Earlier quoted context omitted.

Im not an expert so from my outside viewpoint I think by taking the guitar far away you are implying possibility of faster than light communication, which is thought to be not possible, so his links address that? Hard for me to understand so I'm just saying my thoughts out loud to get clarified, thanks

The quantum state of interest is induced when plucking the conjoined "guitars". (analog for particles) That state is induced at the moment the guitars share "locality" because entanglement requires locality for initialization of polarization. So then, we say we are as yet unaware of the qualities of the polarization we, ourselves, induced. Very mysterious. So spooky, yes? We do not measure, because we choose not to,…

You are missing the point of Bell test experiments. Such experiments demonstrate that which guitar is the high E one and which is the low E one is not decided when they are still together. It is not that you and everyone else just don't know which way it is until someone listens to one of them, it is actually not yet decided until someone listens to one of them.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#82

Post by [deleted] »

danbruc wrote: post #81
crumpington wrote: post #75

Earlier quoted context omitted.

The quantum state of interest is induced when plucking the conjoined "guitars". (analog for particles) That state is induced at the moment the guitars share "locality" because entanglement requires locality for initialization of polarization. So then, we say we are as yet unaware of the qualities of the polarization we, ourselves, induced. Very mysterious. So spooky, yes? We do not measure, because we choose not to,…

You are missing the point of Bell test experiments. Such experiments demonstrate that which guitar is the high E one and which is the low E one is not decided when they are still together. It is not that you and everyone else just don't know which way it is until someone listens to one of them, it is actually not yet decided until someone listens to one of them.

[deleted]

Re: Chinese Researchers Achieve Quantum Entanglement Record

#83

Post by FartyMcFarter »

jblow wrote: post #15
ssdd wrote: post #6

Earlier quoted context omitted.

That's great. Now next thing that needs to be solved is to make this tech available for general public use just like computers are these days. Problems that are waiting to be solved by it are very large and of huge impact.

We all have these things in our pockets that are massive supercomputers by the standards of my college days. And we all use them just to rant at each other about political things that we in reality are totally misinformed about ... and otherwise just waste our lives. I am not sure why quantum computing is supposed to change this. Even software that is supposed to be useful is so terribly slow. Computers are between 2…

Quantum computers are not faster computers that we can use to write lazier code. If they were you might have a point.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#84

Post by marcosdumay »

aaavl2821 wrote: post #56
dzhiurgis wrote: post #49

Earlier quoted context omitted.

A lot of things regarding chemistry and biology - finding catalysts for nitrate fertiliser production (uses 5% of worlds power), perhaps some catalysts in cement production (my idea), invention of new medicines, either due to better cell simulations or (my idea) faster protein folding.

Is the bottleneck preventing better cell simulations computational or lack of data / insufficient understanding of biology to inform a predictive model?

I wouldn't expect a clear bottleneck, because increased computational capacity leads to increased understanding.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#85

Post by abecedarius »

moosinho wrote: post #70
ahelwer wrote: post #25

Earlier quoted context omitted.

The idea that the qbits choose which value they'll collapse to at time of entanglement is called local hidden variable theory, which John Bell disproved in 1964: https://en.wikipedia.org/wiki/Local_hidden_variable_theory In more practical terms, the theory also falls apart when you start doing more complicated things with entangled qbits than just measuring them, like quantum teleportation or error correction.

Can someone tell me if I understand this correctly. So Bell famously proved that it is not the case that the correlation we see between 2 entangled particles A and B is because of some common cause C. Therefore we concluded that it must be that A => B or B => A and we called it a spooky action at a distance. But aren't we forgetting that there's a one more way to get a correlation between A and B without resorting to…

What you're proposing is essentially what Bell's inequalities contradict. That's why they're surprising.

I think the many-worlds picture is a clearer way to think about this than "spooky action at a distance".

Re: Chinese Researchers Achieve Quantum Entanglement Record

#86

Post by klipt »

BookmarkSaver wrote: post #62
aaavl2821 wrote: post #56

Earlier quoted context omitted.

Is the bottleneck preventing better cell simulations computational or lack of data / insufficient understanding of biology to inform a predictive model?

Not an expert, but my understanding is that while better knowledge/models of the biology might be useful, ultimately it's just a massive computational project to test out and optimize protein folding and such complex chemical behavior. The physics/chemistry and biology are understood well enough, there are just nearly countless paths to explore making it a huge problem.

Nature manages to fold proteins quickly enough. What's nature doing that we can't?

Re: Chinese Researchers Achieve Quantum Entanglement Record

#87

Post by avip »

moosinho wrote: post #70
ahelwer wrote: post #25

Earlier quoted context omitted.

The idea that the qbits choose which value they'll collapse to at time of entanglement is called local hidden variable theory, which John Bell disproved in 1964: https://en.wikipedia.org/wiki/Local_hidden_variable_theory In more practical terms, the theory also falls apart when you start doing more complicated things with entangled qbits than just measuring them, like quantum teleportation or error correction.

Can someone tell me if I understand this correctly. So Bell famously proved that it is not the case that the correlation we see between 2 entangled particles A and B is because of some common cause C. Therefore we concluded that it must be that A => B or B => A and we called it a spooky action at a distance. But aren't we forgetting that there's a one more way to get a correlation between A and B without resorting to…

Bell inequality proves (or is used to show) that the shared/correlated state of "entangled" particles cannot be fixed before the act of measurement. It has nothing to say about "A => B" or the likes. If there exists a third "C" it'll still have to set the state of A and B, at the moment of measurement, regardless of distance.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#88

Post by mundo »

moosinho wrote: post #70
ahelwer wrote: post #25

Earlier quoted context omitted.

The idea that the qbits choose which value they'll collapse to at time of entanglement is called local hidden variable theory, which John Bell disproved in 1964: https://en.wikipedia.org/wiki/Local_hidden_variable_theory In more practical terms, the theory also falls apart when you start doing more complicated things with entangled qbits than just measuring them, like quantum teleportation or error correction.

Can someone tell me if I understand this correctly. So Bell famously proved that it is not the case that the correlation we see between 2 entangled particles A and B is because of some common cause C. Therefore we concluded that it must be that A => B or B => A and we called it a spooky action at a distance. But aren't we forgetting that there's a one more way to get a correlation between A and B without resorting to…

Yes, this is more or less what Bell's theorem disproves, although it's kind of a poor metaphor, because entanglement deals with indeterminate states, not just unknown ones.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#89

Post by moefh »

foxes wrote: post #18
reaperducer wrote: post #8

Earlier quoted context omitted.

Problems that are waiting to be solved by it are very large and of huge impact I know virtually nothing about quantum computing, so can you give some examples? Whenever I've asked anyone who seemed to know anything about the field, all they can come up with is weather forecasting and simulating nuclear explosions. Not exactly "general use," as you put it. In the back of my mind, I know that quantum computing is a big…

There are already lots of 'practical' applications in the literature. A famous one is Shor's factorisation algorithm. But there are others - everything from doing pagerank to simulating other quantum systems. Many classical algorithms, which run in ~O(poly(n)) can have an 'equivalent' quantum algorithm in ~O(log(n)) - an exponential speedup. There is still debate as to how the complexity class of problems which are e…

> Its suspected P lies entirely within BQP.

It's actually known that BQP contains P[1]. It also contains BPP. What's not known is the relationship between BQP and NP (most experts suspect there's no containment in either direction).

[1] See this for an easy proof: https://people.eecs.berkeley.edu/~vazirani/f04quantum/notes/...

Re: Chinese Researchers Achieve Quantum Entanglement Record

#90

Post by mundo »

crumpington wrote: post #52
ahelwer wrote: post #25

Earlier quoted context omitted.

The idea that the qbits choose which value they'll collapse to at time of entanglement is called local hidden variable theory, which John Bell disproved in 1964: https://en.wikipedia.org/wiki/Local_hidden_variable_theory In more practical terms, the theory also falls apart when you start doing more complicated things with entangled qbits than just measuring them, like quantum teleportation or error correction.

Big deal. There's nothing shocking or spooky about two billiard balls being made to spin in arbitrarily opposing directions, selecting only one ( omg! without discovering which way it spins, you guys ), then separating them, and then noticing the spin of one, in order to reliably grasp that the other is the reversal. I have two guitars. I place the guitars facing one another, such that plucking the HIGH E string on o…

> There's nothing shocking or spooky about two billiard balls being made to spin in arbitrarily opposing directions, selecting only one, then separating them, and then noticing the spin of one, in order to reliably grasp that the other is the reversal.

Okay. So now, make two billiard balls so that they're spinning opposite directions, and separate them to opposite sides of the table. Then, go to ball A and do something to it that reverses its spin. Then observe the spins of the two balls. Are they the same?

For billiard balls, yes. If ball A is spinning clockwise and ball B is spinning counter-clockwise, and you reverse the spin of ball A, then you will observe both balls to be spinning counter-clockwise.

For quantum particles, no. If we manufacture two entangled electrons such that observing them will reveal them to have opposite spin, you can reverse the spin of one of them, and then observe them, and they will both still have opposite spin.

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