5 ms·

I think your intuition is correct and that Steinberg is agreeing with you here. Steinberg is just saying that a single particle alone cannot generate a causalit

by lacker 6y ago

I think your intuition is correct and that Steinberg is agreeing with you here. Steinberg is just saying that a single particle alone cannot generate a causality paradox. But it still isn't obvious why you couldn't use this effect with multiple bits and some error correct to send signals faster than light. Looking at the paper being discussed here - https://iopscience.iop.org/article/10.1088/1367-2630/abb515/meta https://iopscience.iop.org/article/10.1088/1367-2630/abb515/... - the authors also don't seem to have an explanation. One final caveat worth noting is that our results do not definitively prove that an ensemble of free particles will always be a preferable method of transmitting a signal to an ensemble of tunneled particles. It is our intention to include a discussion of this in a follow-up paper. This is basically the scenario you're talking about, forming several bits out of different particles and using them in conjunction to send information faster than light. The researchers aren't sure why this wouldn't happen in their model.

h0l0cube 6y ago
Given the probabilistic nature of quantum effects I doubt there's a reliable way to tunnel particles. If a tunnelling event happens with low frequency, the receiver would need a side-channel or some redundancy to be sure it had received a signal. But it will be interesting to see what comes up in their follow-up paper.
- enkid 6y ago
  That's why you use multiple. It doesn't matter how unreliable, if it only works on in a million times, you send two million. Still the same concept.
  - h0l0cube 6y ago
    Of course, but in using multiple I wager we would end up with a transmission rate the same or worse than without tunnelling. Might be wrong, but I'll defer to the actual experts on this one.
  - andrewljohnson 6y ago
    Is there an upper bound on how noisy the signal can be and still work?
- dogma1138 6y ago
  We exploit quantum tunneling in many applications, you are posting from a device that wouldn’t work if there was no reliable way to exploit quantum tunneling.
  - h0l0cube 6y ago
    I'd like to know more about that. I know transistor design requires mitigating quantum tunnelling as it unpredictably alters the flow of elections. I doubt there's a way to make tunnelling sufficiently reliable enough to permit a higher transfer rate, but willing to stand corrected.
    - dogma1138 6y ago
      Floating gates use Quantum Tunneling, these are the building blocks of flash memory. https://en.m.wikipedia.org/wiki/Floating-gate_MOSFET https://en.m.wikipedia.org/wiki/Floating-gate_MOSFET Tunnel junctions are used in applications such as photovoltaics as well as high frequency circuits e.g. tunneling diodes. https://en.m.wikipedia.org/wiki/Tunnel_junction https://en.m.wikipedia.org/wiki/Tunnel_junction https://en.m.wikipedia.org/wiki/Tunnel_diode https://en.m.wikipedia.org/wiki/Tunnel_diode
      - h0l0cube 6y ago
        TIL. Awesome. I still remain an arm-chair skeptic, but it's my guess is the reasons it's practical for storage (i.e. you need greater charge to make the tunnel, but the charge is durably stored because it can't tunnel out) don't make it practical for increasing transmission rate vs a direct connection. Edit: Just to fix a confusion, by 'reliable' I meant, one electron sent, one received. I know one 'bit' isn't typically sent as one electron, but being reductive for comparison's sake. Obviously with enough current you can make the tunnel happen, but you'd need far more electrons and 'time' to do so.
        dogma1138 6y ago
        Tunneling diodes are extremely reliable for signaling, which is why they've been used in early high frequency applications such as UHF TV and satellite communications they exhibit "FTL" tunneling just like any other case of electron tunneling. The reason we don't often use tunneling diodes today in most devices is that they are expensive to make compared to many other modern diodes, they are still used in more unique applications including very sensitive scientific equipment and space applications. In general there many types of semiconductors that employ a Quantum Well https://en.wikipedia.org/wiki/Quantum_well https://en.wikipedia.org/wiki/Quantum_well this means that these SCs do RELIABLY utilize quantum tunneling by either inducing it under very specific conditions, or averting it. I'm really not sure what you are skeptical about, without use being able to utilize QT reliably we wouldn't be able to make modern semi-conductors they would either not work because we can't make tunneling happen when we need it too, or won't work because we randomly induce it to happen. It doesn't mean we fully "understand" Quantum Tunneling as in understand exactly why it happens, but we know enough to predict and control it, Quantum Tunneling is to the SC industry what fire was to humanity in general for milenia. We still probably can only roughly model the physics of fire, especially since at the end it's governed by QM effects, but we don't need that in fact we don't even need to understand combustion that well to utilize it. But if you want single electron tunneling then yes it's possible there have been papers about it for a few decades with the latest ones also including some experimental work https://arxiv.org/ftp/arxiv/papers/1204/1204.5539.pdf https://arxiv.org/ftp/arxiv/papers/1204/1204.5539.pdf Single electron transistors are also being actively worked on https://en.wikipedia.org/wiki/Single-electron_transistor https://en.wikipedia.org/wiki/Single-electron_transistor
occamrazor 6y ago
Since tunneling is not reliable, you have to use an error correcting code, which means that you have to send more particles, which takes more time. The two effects balance and you can’t send reliable information faster than c.
- 317070 6y ago
  You could send those particles in parallel though (i.e. make your channel wider in information theory). More particles should not take more time, just more space, which is fine. I was also puzzled by this sentence in the article.
  - TheOtherHobbes 6y ago
    It's not puzzling. It's a statement of faith, not something that has a solid theoretical basis. Any form of FTL causes problems with causality - or at least with current assumptions about causality. So physicists tend to work back from that to "Therefore this is impossible." But those assumptions may turn out to be wrong and relativity may be violated in specific quantum contexts. And then all kinds of interesting things happen. Incidentally, this is an example of the kind of thing Hossenfelder was talking about. You could spend $20bn on a new collider, or you can spend a couple of million - at the absolute most - to check there's nothing unexpected happening here. It's a wild bet, but given the up side it's hard to characterise it as poor value. At worst you'll get some insight into the interface between QM and relativity, with another situation where Relativity Wins Again - but you understand why, in detail. At best you'll get something more challenging and interesting.

by lacker 6y ago

h0l0cube 6y ago

Given the probabilistic nature of quantum effects I doubt there's a reliable way to tunnel particles. If a tunnelling event happens with low frequency, the receiver would need a side-channel or some redundancy to be sure it had received a signal. But it will be interesting to see what comes up in their follow-up paper.

enkid 6y ago
That's why you use multiple. It doesn't matter how unreliable, if it only works on in a million times, you send two million. Still the same concept.
- h0l0cube 6y ago
  Of course, but in using multiple I wager we would end up with a transmission rate the same or worse than without tunnelling. Might be wrong, but I'll defer to the actual experts on this one.
- andrewljohnson 6y ago
  Is there an upper bound on how noisy the signal can be and still work?
dogma1138 6y ago
We exploit quantum tunneling in many applications, you are posting from a device that wouldn’t work if there was no reliable way to exploit quantum tunneling.
- h0l0cube 6y ago
  I'd like to know more about that. I know transistor design requires mitigating quantum tunnelling as it unpredictably alters the flow of elections. I doubt there's a way to make tunnelling sufficiently reliable enough to permit a higher transfer rate, but willing to stand corrected.
  - dogma1138 6y ago
    Floating gates use Quantum Tunneling, these are the building blocks of flash memory. https://en.m.wikipedia.org/wiki/Floating-gate_MOSFET https://en.m.wikipedia.org/wiki/Floating-gate_MOSFET Tunnel junctions are used in applications such as photovoltaics as well as high frequency circuits e.g. tunneling diodes. https://en.m.wikipedia.org/wiki/Tunnel_junction https://en.m.wikipedia.org/wiki/Tunnel_junction https://en.m.wikipedia.org/wiki/Tunnel_diode https://en.m.wikipedia.org/wiki/Tunnel_diode
    - h0l0cube 6y ago
      TIL. Awesome. I still remain an arm-chair skeptic, but it's my guess is the reasons it's practical for storage (i.e. you need greater charge to make the tunnel, but the charge is durably stored because it can't tunnel out) don't make it practical for increasing transmission rate vs a direct connection. Edit: Just to fix a confusion, by 'reliable' I meant, one electron sent, one received. I know one 'bit' isn't typically sent as one electron, but being reductive for comparison's sake. Obviously with enough current you can make the tunnel happen, but you'd need far more electrons and 'time' to do so.
      - dogma1138 6y ago
        Tunneling diodes are extremely reliable for signaling, which is why they've been used in early high frequency applications such as UHF TV and satellite communications they exhibit "FTL" tunneling just like any other case of electron tunneling. The reason we don't often use tunneling diodes today in most devices is that they are expensive to make compared to many other modern diodes, they are still used in more unique applications including very sensitive scientific equipment and space applications. In general there many types of semiconductors that employ a Quantum Well https://en.wikipedia.org/wiki/Quantum_well https://en.wikipedia.org/wiki/Quantum_well this means that these SCs do RELIABLY utilize quantum tunneling by either inducing it under very specific conditions, or averting it. I'm really not sure what you are skeptical about, without use being able to utilize QT reliably we wouldn't be able to make modern semi-conductors they would either not work because we can't make tunneling happen when we need it too, or won't work because we randomly induce it to happen. It doesn't mean we fully "understand" Quantum Tunneling as in understand exactly why it happens, but we know enough to predict and control it, Quantum Tunneling is to the SC industry what fire was to humanity in general for milenia. We still probably can only roughly model the physics of fire, especially since at the end it's governed by QM effects, but we don't need that in fact we don't even need to understand combustion that well to utilize it. But if you want single electron tunneling then yes it's possible there have been papers about it for a few decades with the latest ones also including some experimental work https://arxiv.org/ftp/arxiv/papers/1204/1204.5539.pdf https://arxiv.org/ftp/arxiv/papers/1204/1204.5539.pdf Single electron transistors are also being actively worked on https://en.wikipedia.org/wiki/Single-electron_transistor https://en.wikipedia.org/wiki/Single-electron_transistor

occamrazor 6y ago

Since tunneling is not reliable, you have to use an error correcting code, which means that you have to send more particles, which takes more time. The two effects balance and you can’t send reliable information faster than c.

317070 6y ago
You could send those particles in parallel though (i.e. make your channel wider in information theory). More particles should not take more time, just more space, which is fine. I was also puzzled by this sentence in the article.
- TheOtherHobbes 6y ago
  It's not puzzling. It's a statement of faith, not something that has a solid theoretical basis. Any form of FTL causes problems with causality - or at least with current assumptions about causality. So physicists tend to work back from that to "Therefore this is impossible." But those assumptions may turn out to be wrong and relativity may be violated in specific quantum contexts. And then all kinds of interesting things happen. Incidentally, this is an example of the kind of thing Hossenfelder was talking about. You could spend $20bn on a new collider, or you can spend a couple of million - at the absolute most - to check there's nothing unexpected happening here. It's a wild bet, but given the up side it's hard to characterise it as poor value. At worst you'll get some insight into the interface between QM and relativity, with another situation where Relativity Wins Again - but you understand why, in detail. At best you'll get something more challenging and interesting.