5 ms·

Please provide a brief one, or a few links! I'd love to know.

by dash2 8y ago

marcosdumay 8y ago
You can't choose what is the value you read from an entangled particle, thus you can't choose what value your peer reads either. Your peer will read the inverse value that you read, but that alone does not make any information go through the channel.
- tgb 8y ago
  Oh it's better than that! The term "quantum teleportation" is horribly misleading but that would be a major application of this. What "quantum teleportation" should maybe be thought of is allowing you transmit a quantum bit to someone else by instead (A) sharing an entangled particle pair ahead of time and (B) transmitting two (non-quantum) bits to them over, say, ethernet. If you prepare your half of the entagled particle pair properly and send them the right two (classical) bits, then they will be able to reconstruct your original quantum bit out of their entangled particle. So it's a way of getting my quantum bit to your quantum computer without having to pick it up and move it over there. It doesn't happen faster than the speed of light since it still involves transferring 2 regular bits. And it's not really teleportation, unless I "teleport" an image to you by sending emailing it to you. The main difference with sending regular bits is that you inherently destroy your original quantum bit before you "teleport" it, which is presumably where the name comes from. Since copying quantum bits is impossible (the "no-clone theorem"), you can't work around that destruction either.
  - jfoutz 8y ago
    I know, like, nothing about this. But my wiki reading makes me think this is essentially a one time pad. you share the entangled bits, you send a message, the message tells you what to do if your entangled bit is one, or zero. nobody can mess with the entangled bits, or they lose entanglement, and the message becomes random. i dunno, it seems like if you had a bunch of them you could make a secure channel.
    - marcosdumay 8y ago
      > i dunno, it seems like if you had a bunch of them you could make a secure channel. I don't think anybody solved man in the middle attacks against it yet. If the attacker takes hold of both the entangled channel and the classical channel, he can impersonate both parties and keep the conversation going. And you can't store those pairs. All those articles are about people that made them survive long enough for transmission. So you can't distribute them in person.
      - AlexCoventry 8y ago
        That MITM attack is considerably more fragile than just reading a one-time pad during transit, though.
        marcosdumay 8y ago
        Asymmetric encryption is cheaper, survives storage, requires only the transmission of public data, and is not fundamentally flawed like that. It is also more versatile.
        akvadrako 8y ago
        But non-quantum encryption hasn't been mathematically proven to be secure. In the real world, you'll probably always use both and only if large quantum computers become available.
        marcosdumay 8y ago
        Quantum computers are not needed for quantum encryption, and quantum computers do not break classical encryption in general, just the most used algorithms. They simply don't change the overall picture on this. Yes, non-quantum encryption has not been proven secure. That beats a known insecure systems at any time. You are also underestimating the cost of quantum crypto - it will only work on direct fiber, it can never be routed.
- cube2222 8y ago
  Could you please elaborate? If I understand correctly what is written here, observingicle causes it to increase its, and its peers, state. Wouldn't this let you to decide afterwards if you wanted to again observe it and invert the state if you wanted? Or does observing break entanglement / an inverted particle doesn't get inverted back after another observation?
  - ianai 8y ago
    Entanglement is broken on observation. “Mike and Ike” suggest we may have a “department of entanglement“ someday like we have a DOE. It’s a scarce resource. About the best application I’ve read so far is using entanglement as a signal amplifier (my over simplification).
- flatline 8y ago
  But if you have n entanglements you can get n bits of information from the channel by timing the disentanglements at agreed-upon intervals, no? Like, Morse code...
  - marcosdumay 8y ago
    You can't observe the entanglement breaking. You can only observe the particle's state.

Please provide a brief one, or a few links! I'd love to know.

by dash2 8y ago

Please provide a brief one, or a few links! I'd love to know.

You can't choose what is the value you read from an entangled particle, thus you can't choose what value your peer reads either. Your peer will read the inverse value that you read, but that alone does not make any information go through the channel.

tgb 8y ago
Oh it's better than that! The term "quantum teleportation" is horribly misleading but that would be a major application of this. What "quantum teleportation" should maybe be thought of is allowing you transmit a quantum bit to someone else by instead (A) sharing an entangled particle pair ahead of time and (B) transmitting two (non-quantum) bits to them over, say, ethernet. If you prepare your half of the entagled particle pair properly and send them the right two (classical) bits, then they will be able to reconstruct your original quantum bit out of their entangled particle. So it's a way of getting my quantum bit to your quantum computer without having to pick it up and move it over there. It doesn't happen faster than the speed of light since it still involves transferring 2 regular bits. And it's not really teleportation, unless I "teleport" an image to you by sending emailing it to you. The main difference with sending regular bits is that you inherently destroy your original quantum bit before you "teleport" it, which is presumably where the name comes from. Since copying quantum bits is impossible (the "no-clone theorem"), you can't work around that destruction either.
- jfoutz 8y ago
  I know, like, nothing about this. But my wiki reading makes me think this is essentially a one time pad. you share the entangled bits, you send a message, the message tells you what to do if your entangled bit is one, or zero. nobody can mess with the entangled bits, or they lose entanglement, and the message becomes random. i dunno, it seems like if you had a bunch of them you could make a secure channel.
  - marcosdumay 8y ago
    > i dunno, it seems like if you had a bunch of them you could make a secure channel. I don't think anybody solved man in the middle attacks against it yet. If the attacker takes hold of both the entangled channel and the classical channel, he can impersonate both parties and keep the conversation going. And you can't store those pairs. All those articles are about people that made them survive long enough for transmission. So you can't distribute them in person.
    - AlexCoventry 8y ago
      That MITM attack is considerably more fragile than just reading a one-time pad during transit, though.
      - marcosdumay 8y ago
        Asymmetric encryption is cheaper, survives storage, requires only the transmission of public data, and is not fundamentally flawed like that. It is also more versatile.
        akvadrako 8y ago
        But non-quantum encryption hasn't been mathematically proven to be secure. In the real world, you'll probably always use both and only if large quantum computers become available.
        marcosdumay 8y ago
        Quantum computers are not needed for quantum encryption, and quantum computers do not break classical encryption in general, just the most used algorithms. They simply don't change the overall picture on this. Yes, non-quantum encryption has not been proven secure. That beats a known insecure systems at any time. You are also underestimating the cost of quantum crypto - it will only work on direct fiber, it can never be routed.
cube2222 8y ago
Could you please elaborate? If I understand correctly what is written here, observingicle causes it to increase its, and its peers, state. Wouldn't this let you to decide afterwards if you wanted to again observe it and invert the state if you wanted? Or does observing break entanglement / an inverted particle doesn't get inverted back after another observation?
- ianai 8y ago
  Entanglement is broken on observation. “Mike and Ike” suggest we may have a “department of entanglement“ someday like we have a DOE. It’s a scarce resource. About the best application I’ve read so far is using entanglement as a signal amplifier (my over simplification).
flatline 8y ago
But if you have n entanglements you can get n bits of information from the channel by timing the disentanglements at agreed-upon intervals, no? Like, Morse code...
- marcosdumay 8y ago
  You can't observe the entanglement breaking. You can only observe the particle's state.