7 ms·

Information teleported between two computer chips for the first time

43 points by dsr12 7y ago

api 7y ago
Quantum entanglement can't transfer information because you have no way of knowing whether the other end has "observed" their particle(s) yet. A conventional signal is required to establish this. But... as far as I recall there may be ways to have that conventional signal only carry minimal (e.g. parity) information and thus to achieve not only much higher data rates but physically un-snoopable communication. I wonder if you could pair quantum entanglement with a slow ultra-long-range signal in the low frequency range to achieve high speed perfectly secure long distance links? I assume this sort of thing would be first of interest to military and intelligence users.
- akersten 7y ago
  Regarding the observation problem: Wouldn't you be able to set up a protocol beforehand (e.g. sample the photon at X MHz) and then you know your window for when the other side would have had the chance to observe? Isn't this how a lot of time division multiplexing already works? For me the bigger issue with quantum computing is that I just don't believe it will ever be practical. Feels like we've been seeing this same article for the last 30 years. I'll love to be proven wrong.
- gwbas1c 7y ago
  > Quantum entanglement can't transfer information because you have no way of knowing whether the other end has "observed" their particle(s) yet Maybe I'm misunderstanding this, but this just reminds me of old serial communication without hardware flow control. As long as both sides can send messages to each other, there's special control codes that are included in the stream for flow control.
- knodi 7y ago
  There are many ways to get around this, like side channels.
- deleted 7y ago
  [deleted]
- vitus 7y ago
  You don't need teleportation for secure comms; you just need pairs of entangled qubits (at which point you can just use their measurements as a one-time pad). That said, if you really want to amplify your transmission rate, you'll also need massive ensembles of entangled qubits (i.e. instead of pairs, you'd need N-tuples). Entanglement gets much, much harder to sustain as the ensemble size goes up. Oh, and you'll also want to replenish your entangled ensembles on a regular basis, since they decohere over time, and you can't reuse them across messages (since measurement destroys entanglement)...
riku_iki 7y ago
My bet is it will be first adapted by high-frequency traders.
- kchamplewski 7y ago
  What advantages would it give them though? It's no faster than any existing means of communication since you still need to send classical information along with the quantum, though I guess it's nice that it can be used for almost completely unbreakable encryption. It feels like complete overkill for no practical advantage that I can see.
NSAID 7y ago
>The team managed to send information from one chip to another instantly without them being physically or electronically connected Doesn't current quantum teleportation require optical connectivity because the state transfers along photons? The abstract says >Here, we report the demonstration of chip-to-chip quantum teleportation and genuine multipartite entanglement, the core functionalities in quantum technologies, on silicon-photonic circuitry So while there may not necessarily be a phsyical connection this does require line-of-sight by my read, and "silicon-photonic circuitry" sounds like this is all on one physical board. I guess I don't understand how this is "two different chips" as the article claims. Did they use two photomasks? Baby steps, I suppose.
- krastanov 7y ago
  Any form of quantum "teleportation" requires that the two chips first share a pair of entangles particles. Usually this is done by making the two entangled particles on one of the chips and sending one of the particles to the other chip. Usually the particles are photons for engineering reasons. The quantum teleportation happens after that. Once the particles are entangled, you can destroy yours in a very particular way that forces the other particle to instantaneously become either a copy of the particle you destroyed (i.e. its state is the same) or the opposite of the particle you destroyed (i.e. its state is something like a boolean negation). Only you know which one happened (you learn that when you destroy your particle) and need to send one bit of classical information to the other chip in order for it to know as well. In other words, you can transmit one bit of classical information and sacrifice one entangled pair to "teleport" one qubit of quantum information. It is called teleportation because the quantum information never actually physically moved, rather it instantaneously went to the other chip. To know how to use it, you still need that classical bit to be transmitted in order to know whether the quantum information underwent a boolean negation.
  - umvi 7y ago
    I'm still so confused. I understand what a photon is (ish... I understand it can behave as a particle or wave, but in this case it is a "particle"). How do you "observe" a single photon? How do you "destroy" a single photon "in a particular way"? Heck, how to do keep something moving at the speed of light stuck inside a chip? Create a fiber optic loop somehow? How is the photon introduced into the loop?
umvi 7y ago
I get the feeling this article is extremely inaccurate and that the author doesn't understand quantum mechanics at all. I'm no expert either, but I've heard over and over from experts that FTL information transfer is still impossible even with "teleportation".
- TheFiend7 7y ago
  Agreed, the article is grossly inaccurate and sensationalized.
- notfed 7y ago
  Articles like this come out once per week. And yes, the authors almost always have very little physics experience. (Or are blatantly misleading for the purpose of clickbait.) It's also very tiring that people keep needing to be reminded of the fact that no, faster-than-light communication is still not (and never will be) possible. (Which really does leave us back at this question: if it doesn't get us faster communication, then what advantages do we think quantum teleportation is going to get us?)
  - umvi 7y ago
    > Which really does leave us back at this question: if it doesn't get us faster communication, then what advantages do we think quantum teleportation is going to get us?) I believe currently its most useful property is its ability to detect eavesdropping. With classical information, it is possible to make a copy of information you observe without being detected. With quantum information, the act of observing changes the state, so eavesdropping can be detected somehow[1] > An important and unique property of quantum key distribution is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. This results from a fundamental aspect of quantum mechanics: the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies. By using quantum superpositions or quantum entanglement and transmitting information in quantum states, a communication system can be implemented that detects eavesdropping. If the level of eavesdropping is below a certain threshold, a key can be produced that is guaranteed to be secure (i.e., the eavesdropper has no information about it), otherwise no secure key is possible and communication is aborted. [1] https://en.wikipedia.org/wiki/Quantum_key_distribution https://en.wikipedia.org/wiki/Quantum_key_distribution
carlosdp 7y ago
> Our current understanding of physics says that nothing can travel faster than the speed of light, and yet, with quantum teleportation, information appears to break that speed limit. The word “information” could be interpreted to mean communication faster than the speed of light, which is important to note is not made possible by entanglement. Entanglement can’t be used for faster-than-light communication because although observing the spin of particle A affects the spin observed for particle B, the spin you observe is effectively random, so there’s no way to know that the results match up unless you compare them with another means of communication, one that is at most the speed of light. This article explains it way better: https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-reasons-quantum-entanglement-doesnt-allow-faster-than-light-communication/ https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-r...
- umvi 7y ago
  However, the article claims: > Changing the properties of one particle will cause the other to instantly change too Is this true? Doesn't that mean if we can control the spin of one particle on command, the other will instantly change according to our control? So basically, FTL communication is possible iff controlling the spin of a particle is possible.
  - boublepop 7y ago
    Think of it this way. We have a pair of gloves. By the nature of pairs of gloves one is right and one is left. We mix them randomly and put them both in closed boxes. Then we classically ship one box at below speed of light to Mars. Now someone on mars if they open their box will “instantaneously” know at above speed of light correlation which glove was in our box back on earth. But no information was transmitted through the revealing itself, and in fact you would need a classical below speed of light bit stream to accompany the quantum glove boxes if you want to use it for communication. In reality there’s some extra concepts to the quantum states because they act as though the selection of which glove is in which box doesn’t happen until we force the gloves into a definite state through opening the box. But that doesn’t change the nature of there being no information transfer. You can do the same sort of above speed of light signaling fully classically. If you for instance consider a lighthouse with a single beam switching between two far away points. One location will know instantly the signal the other receives, but since you aren’t controlling the lighthouse moving back and forth you can’t transfer information through the signal.
deleted 7y ago
[deleted]
secondo 7y ago
Whereas we can’t send specific information between two entangled qubits would we not be able to use it synchronize state (read seed) FTL? That state would for instance allow the two systems to instantly be in sync with a newly generated random seed?
ibobev 7y ago
As always with such articles, this is also misleading. They do not explain that according to the "No-communication theorem" [1] it is not possible to use quantum teleportation for faster than light information transfer. This is becoming very common in popular science articles to be represented some misleading propositions by avoiding to report a little, but important part of the whole picture. In this way many people (sometimes including myself) stayed with invalid picture for what is actually achieved or possible to achieve. [1] https://en.wikipedia.org/wiki/No-teleportation_theorem https://en.wikipedia.org/wiki/No-teleportation_theorem
khkjrhwer 7y ago
One interesting theory of why a maximum speed of communication (speed of light) exists is that it allows simulating the universe in a distributed way, since it gives you a maximum effect range (light cone), thus you can shard your simulation (of course, you still need to sync neighbor shards).
- vjktyu 7y ago
  There is a simpler explanation. Assuming our world is discrete, like a mathematical graph, every world state has one or a few next possible states. If we imagine all possible states from past and future linked together by causality links as a huge mathematical graph, any two states have a shortest path between them. The length of this path is what we perceive as time or as the speed of light. Same idea applies to chess: there is large, but finite, number of chess board states and they are linked by moves allowed by the chess rules; the number of moves on the shortest path connecting two positions is what we'd call the speed of light in chess.

43 points by dsr12 7y ago

api 7y ago

Quantum entanglement can't transfer information because you have no way of knowing whether the other end has "observed" their particle(s) yet. A conventional signal is required to establish this. But... as far as I recall there may be ways to have that conventional signal only carry minimal (e.g. parity) information and thus to achieve not only much higher data rates but physically un-snoopable communication. I wonder if you could pair quantum entanglement with a slow ultra-long-range signal in the low frequency range to achieve high speed perfectly secure long distance links? I assume this sort of thing would be first of interest to military and intelligence users.

akersten 7y ago
Regarding the observation problem: Wouldn't you be able to set up a protocol beforehand (e.g. sample the photon at X MHz) and then you know your window for when the other side would have had the chance to observe? Isn't this how a lot of time division multiplexing already works? For me the bigger issue with quantum computing is that I just don't believe it will ever be practical. Feels like we've been seeing this same article for the last 30 years. I'll love to be proven wrong.
gwbas1c 7y ago
> Quantum entanglement can't transfer information because you have no way of knowing whether the other end has "observed" their particle(s) yet Maybe I'm misunderstanding this, but this just reminds me of old serial communication without hardware flow control. As long as both sides can send messages to each other, there's special control codes that are included in the stream for flow control.
knodi 7y ago
There are many ways to get around this, like side channels.
deleted 7y ago
[deleted]
vitus 7y ago
You don't need teleportation for secure comms; you just need pairs of entangled qubits (at which point you can just use their measurements as a one-time pad). That said, if you really want to amplify your transmission rate, you'll also need massive ensembles of entangled qubits (i.e. instead of pairs, you'd need N-tuples). Entanglement gets much, much harder to sustain as the ensemble size goes up. Oh, and you'll also want to replenish your entangled ensembles on a regular basis, since they decohere over time, and you can't reuse them across messages (since measurement destroys entanglement)...

riku_iki 7y ago

My bet is it will be first adapted by high-frequency traders.

kchamplewski 7y ago
What advantages would it give them though? It's no faster than any existing means of communication since you still need to send classical information along with the quantum, though I guess it's nice that it can be used for almost completely unbreakable encryption. It feels like complete overkill for no practical advantage that I can see.

NSAID 7y ago

>The team managed to send information from one chip to another instantly without them being physically or electronically connected Doesn't current quantum teleportation require optical connectivity because the state transfers along photons? The abstract says >Here, we report the demonstration of chip-to-chip quantum teleportation and genuine multipartite entanglement, the core functionalities in quantum technologies, on silicon-photonic circuitry So while there may not necessarily be a phsyical connection this does require line-of-sight by my read, and "silicon-photonic circuitry" sounds like this is all on one physical board. I guess I don't understand how this is "two different chips" as the article claims. Did they use two photomasks? Baby steps, I suppose.

krastanov 7y ago
Any form of quantum "teleportation" requires that the two chips first share a pair of entangles particles. Usually this is done by making the two entangled particles on one of the chips and sending one of the particles to the other chip. Usually the particles are photons for engineering reasons. The quantum teleportation happens after that. Once the particles are entangled, you can destroy yours in a very particular way that forces the other particle to instantaneously become either a copy of the particle you destroyed (i.e. its state is the same) or the opposite of the particle you destroyed (i.e. its state is something like a boolean negation). Only you know which one happened (you learn that when you destroy your particle) and need to send one bit of classical information to the other chip in order for it to know as well. In other words, you can transmit one bit of classical information and sacrifice one entangled pair to "teleport" one qubit of quantum information. It is called teleportation because the quantum information never actually physically moved, rather it instantaneously went to the other chip. To know how to use it, you still need that classical bit to be transmitted in order to know whether the quantum information underwent a boolean negation.
- umvi 7y ago
  I'm still so confused. I understand what a photon is (ish... I understand it can behave as a particle or wave, but in this case it is a "particle"). How do you "observe" a single photon? How do you "destroy" a single photon "in a particular way"? Heck, how to do keep something moving at the speed of light stuck inside a chip? Create a fiber optic loop somehow? How is the photon introduced into the loop?

umvi 7y ago

I get the feeling this article is extremely inaccurate and that the author doesn't understand quantum mechanics at all. I'm no expert either, but I've heard over and over from experts that FTL information transfer is still impossible even with "teleportation".

TheFiend7 7y ago
Agreed, the article is grossly inaccurate and sensationalized.
notfed 7y ago
Articles like this come out once per week. And yes, the authors almost always have very little physics experience. (Or are blatantly misleading for the purpose of clickbait.) It's also very tiring that people keep needing to be reminded of the fact that no, faster-than-light communication is still not (and never will be) possible. (Which really does leave us back at this question: if it doesn't get us faster communication, then what advantages do we think quantum teleportation is going to get us?)
- umvi 7y ago
  > Which really does leave us back at this question: if it doesn't get us faster communication, then what advantages do we think quantum teleportation is going to get us?) I believe currently its most useful property is its ability to detect eavesdropping. With classical information, it is possible to make a copy of information you observe without being detected. With quantum information, the act of observing changes the state, so eavesdropping can be detected somehow[1] > An important and unique property of quantum key distribution is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. This results from a fundamental aspect of quantum mechanics: the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies. By using quantum superpositions or quantum entanglement and transmitting information in quantum states, a communication system can be implemented that detects eavesdropping. If the level of eavesdropping is below a certain threshold, a key can be produced that is guaranteed to be secure (i.e., the eavesdropper has no information about it), otherwise no secure key is possible and communication is aborted. [1] https://en.wikipedia.org/wiki/Quantum_key_distribution https://en.wikipedia.org/wiki/Quantum_key_distribution

carlosdp 7y ago

> Our current understanding of physics says that nothing can travel faster than the speed of light, and yet, with quantum teleportation, information appears to break that speed limit. The word “information” could be interpreted to mean communication faster than the speed of light, which is important to note is not made possible by entanglement. Entanglement can’t be used for faster-than-light communication because although observing the spin of particle A affects the spin observed for particle B, the spin you observe is effectively random, so there’s no way to know that the results match up unless you compare them with another means of communication, one that is at most the speed of light. This article explains it way better: https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-reasons-quantum-entanglement-doesnt-allow-faster-than-light-communication/ https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-r...

umvi 7y ago
However, the article claims: > Changing the properties of one particle will cause the other to instantly change too Is this true? Doesn't that mean if we can control the spin of one particle on command, the other will instantly change according to our control? So basically, FTL communication is possible iff controlling the spin of a particle is possible.
- boublepop 7y ago
  Think of it this way. We have a pair of gloves. By the nature of pairs of gloves one is right and one is left. We mix them randomly and put them both in closed boxes. Then we classically ship one box at below speed of light to Mars. Now someone on mars if they open their box will “instantaneously” know at above speed of light correlation which glove was in our box back on earth. But no information was transmitted through the revealing itself, and in fact you would need a classical below speed of light bit stream to accompany the quantum glove boxes if you want to use it for communication. In reality there’s some extra concepts to the quantum states because they act as though the selection of which glove is in which box doesn’t happen until we force the gloves into a definite state through opening the box. But that doesn’t change the nature of there being no information transfer. You can do the same sort of above speed of light signaling fully classically. If you for instance consider a lighthouse with a single beam switching between two far away points. One location will know instantly the signal the other receives, but since you aren’t controlling the lighthouse moving back and forth you can’t transfer information through the signal.

deleted 7y ago

[deleted]

secondo 7y ago

Whereas we can’t send specific information between two entangled qubits would we not be able to use it synchronize state (read seed) FTL? That state would for instance allow the two systems to instantly be in sync with a newly generated random seed?

ibobev 7y ago

As always with such articles, this is also misleading. They do not explain that according to the "No-communication theorem" [1] it is not possible to use quantum teleportation for faster than light information transfer. This is becoming very common in popular science articles to be represented some misleading propositions by avoiding to report a little, but important part of the whole picture. In this way many people (sometimes including myself) stayed with invalid picture for what is actually achieved or possible to achieve. [1] https://en.wikipedia.org/wiki/No-teleportation_theorem https://en.wikipedia.org/wiki/No-teleportation_theorem

khkjrhwer 7y ago

One interesting theory of why a maximum speed of communication (speed of light) exists is that it allows simulating the universe in a distributed way, since it gives you a maximum effect range (light cone), thus you can shard your simulation (of course, you still need to sync neighbor shards).

vjktyu 7y ago
There is a simpler explanation. Assuming our world is discrete, like a mathematical graph, every world state has one or a few next possible states. If we imagine all possible states from past and future linked together by causality links as a huge mathematical graph, any two states have a shortest path between them. The length of this path is what we perceive as time or as the speed of light. Same idea applies to chess: there is large, but finite, number of chess board states and they are linked by moves allowed by the chess rules; the number of moves on the shortest path connecting two positions is what we'd call the speed of light in chess.