Oxford researchers pull off quantum first with distributed gate teleportation Oxford University researchers have taken a significant step toward large-scale distributed quantum computing by demonstrating the first successful quantum teleportation of a controlled quantum gate between two modules. Published in Nature, the study doesn't claim to be the first to achieve quantum teleportation - after all, …
With articles like this, my A grade at Physics A Level is woefully inadequate. It was nearly 40 years ago. We didn't even get to Einstein's work. All Newton et al.
Forty+ years ago quantum entanglement was still considered tainted with heresy even after 10 years after J S Bell's 1964 paper and the then recent (1972) early confirmatory experiments.
Physicists are as daft as the rest of the population - I had to really scratch my head when one presumably more daft stated authoritatively that Bells Inequality was incompatible with the Bohmian interpretation of quantum mechanics (it's not). Bell himself is on record as stating the inherent non-local nature of David Bohm's theory was a significant source of inspiration. See Goldstein's Bell Paper.
Undergraduate Quantum Mechanics was largely 'don't ask questions - "shut up and calculate.†"' Possibly still is.
† Apparently from a criticism in What's Wrong with this Pillow?, N. David Mermin Physics Today 42 (4), 9–11<(1989) (pg 1, para 4 (col 2))
I got a B at A level Physics some 35 years ago, but the closest I come to doing anything relevant now is watching Brian Cox on the TV. I don't really remember any of it!
All this quantum stuff is so ridiculously beyond me I can't even see it with a telescope. Interesting though!
watching Brian Cox on the TV
well, he was excellent in 'Succession'.
(Sorry, sorry, I know you meant Professor Brian Cox, the one with the hair and previously keyboard player with D:Ream, but I just could not resist. It is a cold wet day in February here in Reading UK, and I needed a little something to cheer me up. Have an upvote by way of apology for my silliness.)
Well, if my A in A Level Physics taught me one thing it was that there was an awful lot more that I didn't know about a lot of things. It got even worse with my degree. And that was over 40 years ago and they have invented even more physics since then. But I still enjoy hearing about Quantum and Relativistic Physics subjects - typically Don Lincoln on the FermiLab channel or Matt O'Dowd on PBS Space Time. The universe is a weird place (even outside of social media).
"We deterministically teleport a controlled-Z (CZ) gate between two circuit qubits in separate modules, achieving 86% fidelity,"
They managed to transmit a particular logic gate implemented using qubits between here and somewhere else, with an 86% chance that it would be there at the end.
It means they are able to join this bit of a quantum computer with a bit of another quantum computer together. A bit like a distributed server/computation problem - you can make two computers work on the same thing even though they're far apart. However, quantum physics says it doesn't matter how far apart they are anyway. You could literally have computers at opposite ends of the universe and link them like this. That's the old "spooky action at a distance".
They say themselves that until that "chance" is 99.9% it's probably not practically useful (despite the earlier talk about determinism).
Basically, they can wire two quantum computers together at an arbitrary distance with a 14% "signal loss" between them.
(This has been your ELI5 explanation, please don't ask me to make it 100% correct because I can't).
“deterministically teleported a fundamental two-qubit quantum gate across two meters of optical fiber, linking two separate quantum modules.”
I don’t pretend to understand from the article what went on in the experiment but the optical fibre might be a limiting factor on interplanetary use.
I may be wrong as my knowledge of quantum physics is limited, but I suspect that the speed of light isn't the limiting factor with quantum entangled states. It is a hugely complex and counter intuitive area. I think that the "quantum state information" is transmitted instantaneously between quantum entangled particles, but if you try to use that for sending faster than speed of light communications it wouldn't work as you would effectively get random noise out at the other end.
I'll just add that you are partly correct. The speed of light would be a limiting factor in setting up the initial quantum states and the physical separation of the entangled particles. This is the equivalent of loading a calculation into RAM ready to be processed. But the actual execution of the calculation by the quantum computer would be done instantaneously.
I haven't looked at the paper, but the defining thing about entanglement is it's "faster than light" (non local). However additional information is needed to unscramble it, so useful information can't travel FTL. Which is an elaborate way of agreeing it will be light-limited.
Explaining the FTL bit is where your chosen interpretation of Quantum Mechanics comes in: what are you willing to sacrifice?
Is the end point of this research, two quantum computers, physically separated, but running in-step?
Useful if one computer is on Earth and the other on the Mars.
Even with entangled systems you still cannot transmit information faster than light so in future we will still have to wait 4 to 24 minutes to receive the edicts of the sometime Karen of Space and future autocrat of Mars.
I think there's also a paradox in there about how you'd prove it…
I think that, one day, we might find effects that look like FTL communication might be possible but it'll turn out to be a "dimensional issue" or never applicable so getting the results of the 3:30 at Chepchester before the start of the race is still a no-goer.
I refer you to The Meaning of Liff:*
"Peakirk n. One who regularly points out that there are no lavatories on the USS Enterprise."
*(Actually, having checked, I find it's in Afterliff.)
According to some "plans" I've seen over the years, the original series Enterprise Bridge had a service channel duct as a buffer between the rear of the bridge consoles & inner\outer hull skins.
The bridge lavatories apparently are discreetly placed to the right hand (& left?) side of the main view screen extending into that service access tunnel..
I don't know about you, but when I go to download my personal log, when I'm done I wouldn't want to come out to at least 3 pairs of command crew eyes on me as I evacuate the facility, especially if there are Klingons on the main screen at the time.
They don't need to go to the toilet in Star Trek because they can transport whatever is in their bladder straight out into space. Although hopefully they'd work out how to avoid beaming out your bladder at the same time (or other parts of your guts!). They should also be able to make light bulbs containing a perfect vacuum by beaming out all of the air from them.
Think of the fibre link as background, but necessary infrastructure. While entangled particles need to separate via the fibre link, they are not what is being "teleported". What does get subsequently teleported is the quantum entanglement state of one of the particles to the other particle, and this happens instantaneously and doesn't use the fibre link.
"for large computations, the probability of successfully completing a computation without any failures becomes exponentially small."
In theory, the infinite improbability drive would make it infinitely improbable that anything would go wrong. It was not successful, however, ending in a "Spontaneous Massive Existence Failure." This was because, in these earlier times when the nature of improbability was less well understood, it was not appreciated that any event that is infinitely improbable will, by definition, occur almost immediately.
So whilst it's possible to generate a small but finite amount of quantum entanglement, the probability of generating the infinite amount of entanglement they'd need for a usable and error free quantum computer of the kind that is capable of working out the sorts of universal problems that they wanted to use it for would, in fact, be exponentially small. So all you'd have to do is work out exactly how many qubits you'd need, feed that number into the trapped-ion quantum computer, give it a fresh cup of really cold liquid nitrogen, and turn it on.
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