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Chinese Researchers Achieve Quantum Entanglement Record

scientificamerican.com

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Re: Chinese Researchers Achieve Quantum Entanglement Record

#61

Post by thatcherc »

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?

My understanding as a physics undergrad is that we can write down the 'equations of motion' of molecular systems with Hamiltonians describing the energies and correlations of the electrons in a system, but they very quickly become intractably difficult to solve. You're trying to solve a very, very big eigenvalue problem.

However, with the right kind of quantum computer or quantum simulator, you could construct a system of qubits that is described by the exact same Hamiltonian. That way, the quantum state of your qubits and your original system would behave in exactly the same way. Then, you just let the qubits evolve in time and read out the system's state at the end. Do that a bunch of times and you'll see an average picture of what the original system you're modelling (protein or something) would do.

So to recap - we can get around the difficult compute bottleneck caused by the desire to perform high-fidelity physics simulations by creating a system that follows the same rules and which we can probe much more easily.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#62

Post by BookmarkSaver »

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?

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.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#63

Post by tzahola »

Erlich_Bachman wrote: post #27
jblow wrote: post #15

Earlier quoted context omitted.

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…

> 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. So if I decide to use the device that I have bought and invested in, to "rant" about something (to connect to other people through it, essentially), or even just connect to my loved ones sending "meaningless" information (as many I'm sure would call it), or i…

What a long-winded way to say: "That's just your opinion"

Re: Chinese Researchers Achieve Quantum Entanglement Record

#64

Post by Filligree »

madeuptempacct wrote: post #47
nabla9 wrote: post #42

Earlier quoted context omitted.

It works like normal radar, except that they send one entangled photon towards the plane and keep the other. When the reflection returns, they can use the entanglement to sort out signal from noise much better and radar is safe from jamming and spoofing.

Thanks, this helps a lot, but just to clarify: Originally "We 'shine' a bunch of photons at an object, and see if they come back. Except there could be dragged decoy spamming photons back at us, and we don't know if there is. Or it could be sending out so much light, our photons coming back are lost in the mix." With quantum: "We can verify that any photons that get reflected are the ones that we sent out and check o…

Right. Oversimplifying a lot, it's putting a name tag on the photons. Then you can sort out the tagged ones from all the others, drastically reducing the practical noise floor.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#65

Post by tzahola »

_match wrote: post #55
jblow wrote: post #15

Earlier quoted context omitted.

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…

Honestly, I'd love to see examples of rotted code that could be made exponentially faster. I'm likely guilty of this. And I agree that it's disheartening to watch how horribly we use these incredible tools. But thankfully as programmers we're in a position to design these tools to offset the worst parts of humanity. And one field in which more powerful computers will be needed soon is deep learning. It appears that p…

>And one field in which more powerful computers will be needed soon is deep learning. It appears that progress is beginning to stall, as larger networks are necessary. Better tools for distributed computing will make up the difference in the short term, but the current infrastructure appears to be insufficient for general intelligence.

"In 50 years, every street in London will be buried under nine feet of manure."

Re: Chinese Researchers Achieve Quantum Entanglement Record

#66

Post by crumpington »

ChrisClark wrote: post #58
crumpington wrote: post #52

Earlier quoted context omitted.

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…

https://en.wikipedia.org/wiki/Local_hidden_variable_theory https://en.wikipedia.org/wiki/Bell_test_experiments#Hensen_e...

These links are intended to suggest something contrary to what I've said, but they do not suggest any contradiction.

Re: Chinese Researchers Achieve Quantum Entanglement Record

#67

Post by 21 »

barbegal wrote: post #45
tzakrajs wrote: post #38

> “It’s as though you took six bits in your computer, but each bit tripled in how much information it could hold,” Schreppler said "Each bit is tripled in how much information it could hold"? Normally bits have two states, but Shreppler is claiming these qubits can have six states? What am I missing?

It's a confusing quote. They have achieved 18 qubits from 6 photons. But 18 qubits can store more information than 18 regular bits however when the 6 photon system is measured the quantum state collapses to 18 bits of data. How do you get 18 qubits from 6 photons? You use multiple degrees of freedom. Whereas a bit in traditional memory has a single degree of freedom (electric charge), photons have many degrees of fre…

Even in traditional memory, you can use a single degree of freedom to store multiple bits, by quantizing the charge. Like in TLC flash memory, where you can store 3 bit per cell.

This is because in traditional memory, a single "cell" stores many elementary charges (electrons).

Re: Chinese Researchers Achieve Quantum Entanglement Record

#70

Post by moosinho »

ahelwer wrote: post #25
bdamm wrote: post #24

Earlier quoted context omitted.

The part I don't understand is the "spooky action at a distance." Isn't this just the same as if the qbits were already in whatever their final state was as soon as they were entangled? Or in other words, is there any experimental basis for determining that the "cat" stayed alive at all? It seems a lot less magical when we just determine that in fact the value is the same no matter when or where you measure it, altho…

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 spooky action at a distance - conditioning on a common effect, aka collider: http://www.the100.ci/2017/03/14/that-one-weird-third-variabl... Has anyone proven that this is not the case?
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