4 ms·

Quantum researchers cause controlled 'wobble' in the nucleus of a single atom

72 points by gmays 2y ago

notum 2y ago
CTRL+F "entanglement". Disappointed. No interstellar comms for us.
- roywiggins 2y ago
  Entanglement isn't particularly useful for communication, you can't send bits without sending photons (or similar) physically. Quantum mechanics doesn't permit ansibles as far as anyone knows.
  - josefritzishere 2y ago
    I had to google ansible. https://en.wikipedia.org/wiki/Ansible https://en.wikipedia.org/wiki/Ansible
  - aatd86 2y ago
    Is it the issue or is it rather than any measurement of entangled quantum state change is modifying the measurement to the extent that there is a chicken and egg problem? Basically reading quantum data is also a write operation?
    - eigenket 2y ago
      The issue the person above is alluding to is known as the no communication theorem. It has a wiki page https://en.m.wikipedia.org/wiki/No-communication_theorem https://en.m.wikipedia.org/wiki/No-communication_theorem But the upshot is basically that entanglement doesn't let you do anything unless you send some classical data as well.
      - aatd86 2y ago
        Thanks. The reason still seem to be related to the uncertainty principle although I am not sure. The same way they explain no-cloning but it seems to be analogous to identity within a system with interaction from neighboring data. Ultimately there is no pure independent state. Data always exists within context. Hence causality and spatial preservation (no instant physical teleportation as far as is currently understood). (in very layman's terms)
  - eigenket 2y ago
    While the second and third parts if your comment are complete true, the first part > Entanglement isn't particularly useful for communication I would say is false. Entanglement lets you do some fun and theoretically useful stuff for communication tasks. At the most basic level sharing entanglement lets you upgrade a classical communication channels you have into a quantum one (sending 2 bits and burning an entangled pair lets you send a qubit). You can do increasing fancy stuff if you so wish, if you are sufficiently paranoid you might be interested in device independent cryptography, which is only possible because of entanglement.
    - roywiggins 2y ago
      Yes, they are fun, but not notably useful, at least not yet. And only useful for pretty specialized tasks like key exchange.
      - quantadev 2y ago
        Isn't it true that in key exchange entanglement isn't used in any way shape or form for sending data, but only in making a determination that there was no eavesdropping on the transmission, because any eavesdropper would collapse the wave function. So like you said, entanglement can't be used to send information, but it can be used to detect if the transmission was secure (I think)
        eigenket 2y ago
        There are many protocols for quantum key distribution/exchange so it's hard to answer fully without knowing which one you're talking about. That said their are protocols, like the one invented by Artur Ekert in 1991, which use entanglement in an essential way to transmit the key. Even in the absence of an evesdropper the protocol will not work without entanglement. It escapes the no-communication theorem by also requiring some classical communication.
        quantadev 2y ago
        Right, if you expand the scope of the discussion to other areas other than sending bits, there are various ways entanglement is used in various protocols. But none of them utilize entanglement to be able to get a bit from Alice to Bob faster than light can go.
  - bloopernova 2y ago
    I am unable to grasp why FTL communication would break causality, it's like my brain just refuses to accept it. Seriously, I've had it explained several times over the years.
    - shepardrtc 2y ago
      When you communicate, you're sending energy - whether it's sound waves or radio waves or whatever. Energy can't travel faster than c through spacetime. Now if you manipulate spacetime, such as a wormhole or whatever, then the end result can effectively appear as if it's FTL but its still going at c, its just traveling through less/compressed space.
    - eigenket 2y ago
      Its probably mostly because you have an intuitive idea that there is some concept of "now" which is independent of the observer. In special relativity this global "now" isn't a thing. It doesn't exist. There is no global now. Different observers who are in different places and/or moving at different speeds will describe different events as simultaneous. In particular say we have an observer who sees an event A happening at time 0, and a second event (call it B) at time t and the distance between them is greater than c t. Then you can find observers who see A happening first, B happening first or the two happening at the same time. However all observers will agree that the distance between the events was greater than c times the time between them. This seems like it would cause problems with causality, but it doesn't because we need the distance to be greater than c times the time, which means no lightspeed signal could get from A to B. If you allow ftl communication then this "escape" doesn't work anymore, and causality can be explicitly broken.
    - rogerclark 2y ago
      You can't grasp this because there is no FTL communication. Quantum entanglement does not enable FTL communication, and wormholes etc. are entirely theoretical.
      - roywiggins 2y ago
        It doesn't even enable STL communication, other than eg superdense coding and similar. But that's not what people mean when they think entanglement can be used for communication.
unsupp0rted 2y ago
For MRI / medical imaging, if nuclear wobbling can enhance signal strength, it might be possible to achieve high-quality images using lower-strength magnetic fields, and much faster. Maybe even ones that fit in a backpack and unfold.
- pbhjpbhj 2y ago
  For comparison, it seems the smallest portable MRI presently are ~600kg, like the Hyperfine Swoop https://hyperfine.io/swoop/overview https://hyperfine.io/swoop/overview (not affiliated).
gaze 2y ago
I’m not totally sure what makes this result so novel but also that’s probably due to my ignorance. Hyperfine qubits are pretty common using neutral atoms, and you can do imaging on the hyperfine states. Is the novelty here that the electron spin is on resonance with the nuclear spin and that it’s done with STM? I guess I don’t see how pump-probe is so much more direct than using an imaging transition.
- quantadev 2y ago
  I think the key thing they were pointing out was the ability to store information inside a nucleus that can be read back (reminds me of how core memory worked on the old Apollo 11 Era computers) which could be a very reliable and dense memory. It's reliable because the electron shell is sort of protecting the information stored inside the nucleus. I wonder if they'll have the same issue that core memory also had which is that by reading the magnetic state you also destroy that state, and so every bit 'read' operation has to be followed with a 'now write the bit back again' step.
acidburnNSA 2y ago
Big dream of mine would be to align nuclei of nuclear fuel atoms just so and then induce fission in such a way as to get one delayed neutron precursor and one other quick-to-stability fission product. This would allow fission power without any long-lived waste products or afterglow heat cooling challenges that dominate accident risk. Physicist friends have told me it's impossible. I've only accepted impractical for now.
- AtlasBarfed 2y ago
  You want an msr/LFTR and breed away the bad waste.
- colechristensen 2y ago
  You're thinking about the atom very classically, At the scale of the nucleus things just don't "exist" in "places". Processes are truly random and things literally don't have position/momentum/rotation/alignment until you do the thing that requires them to decide where they were and what they were doing at the time. Simpler than nuclear physics is just the electron. There is no meaningful answer to where it is around an atom at any particular time. You can either get a location or a momentum or half the information about each if you poke it, but that's just its response to being poked, it wasn't "actually" there until you poked it.
  - im3w1l 2y ago
    From what I recall, quantum things have well defined states, even if those states may not correspond to position / momentum / rotation / alignment. By correctly molding the energy landscape it may be possible to set the states and state transitions up in a beneficial way for what he proposed.
    - colechristensen 2y ago
      Eh, not really. You can futz with the probability distribution, like a fast neutron will cause a different distribution of fission products than a slow one... but it is still a very random process. You can't control it like an expert at a billiards table. Especially the strong force mediated interactions between particles in the nucleus. Some people just won't believe you though.
kamalamomala 2y ago
[flagged]

72 points by gmays 2y ago

notum 2y ago

CTRL+F "entanglement". Disappointed. No interstellar comms for us.

roywiggins 2y ago
Entanglement isn't particularly useful for communication, you can't send bits without sending photons (or similar) physically. Quantum mechanics doesn't permit ansibles as far as anyone knows.
- josefritzishere 2y ago
  I had to google ansible. https://en.wikipedia.org/wiki/Ansible https://en.wikipedia.org/wiki/Ansible
- aatd86 2y ago
  Is it the issue or is it rather than any measurement of entangled quantum state change is modifying the measurement to the extent that there is a chicken and egg problem? Basically reading quantum data is also a write operation?
  - eigenket 2y ago
    The issue the person above is alluding to is known as the no communication theorem. It has a wiki page https://en.m.wikipedia.org/wiki/No-communication_theorem https://en.m.wikipedia.org/wiki/No-communication_theorem But the upshot is basically that entanglement doesn't let you do anything unless you send some classical data as well.
    - aatd86 2y ago
      Thanks. The reason still seem to be related to the uncertainty principle although I am not sure. The same way they explain no-cloning but it seems to be analogous to identity within a system with interaction from neighboring data. Ultimately there is no pure independent state. Data always exists within context. Hence causality and spatial preservation (no instant physical teleportation as far as is currently understood). (in very layman's terms)
- eigenket 2y ago
  While the second and third parts if your comment are complete true, the first part > Entanglement isn't particularly useful for communication I would say is false. Entanglement lets you do some fun and theoretically useful stuff for communication tasks. At the most basic level sharing entanglement lets you upgrade a classical communication channels you have into a quantum one (sending 2 bits and burning an entangled pair lets you send a qubit). You can do increasing fancy stuff if you so wish, if you are sufficiently paranoid you might be interested in device independent cryptography, which is only possible because of entanglement.
  - roywiggins 2y ago
    Yes, they are fun, but not notably useful, at least not yet. And only useful for pretty specialized tasks like key exchange.
    - quantadev 2y ago
      Isn't it true that in key exchange entanglement isn't used in any way shape or form for sending data, but only in making a determination that there was no eavesdropping on the transmission, because any eavesdropper would collapse the wave function. So like you said, entanglement can't be used to send information, but it can be used to detect if the transmission was secure (I think)
      - eigenket 2y ago
        There are many protocols for quantum key distribution/exchange so it's hard to answer fully without knowing which one you're talking about. That said their are protocols, like the one invented by Artur Ekert in 1991, which use entanglement in an essential way to transmit the key. Even in the absence of an evesdropper the protocol will not work without entanglement. It escapes the no-communication theorem by also requiring some classical communication.
        quantadev 2y ago
        Right, if you expand the scope of the discussion to other areas other than sending bits, there are various ways entanglement is used in various protocols. But none of them utilize entanglement to be able to get a bit from Alice to Bob faster than light can go.
- bloopernova 2y ago
  I am unable to grasp why FTL communication would break causality, it's like my brain just refuses to accept it. Seriously, I've had it explained several times over the years.
  - shepardrtc 2y ago
    When you communicate, you're sending energy - whether it's sound waves or radio waves or whatever. Energy can't travel faster than c through spacetime. Now if you manipulate spacetime, such as a wormhole or whatever, then the end result can effectively appear as if it's FTL but its still going at c, its just traveling through less/compressed space.
  - eigenket 2y ago
    Its probably mostly because you have an intuitive idea that there is some concept of "now" which is independent of the observer. In special relativity this global "now" isn't a thing. It doesn't exist. There is no global now. Different observers who are in different places and/or moving at different speeds will describe different events as simultaneous. In particular say we have an observer who sees an event A happening at time 0, and a second event (call it B) at time t and the distance between them is greater than c t. Then you can find observers who see A happening first, B happening first or the two happening at the same time. However all observers will agree that the distance between the events was greater than c times the time between them. This seems like it would cause problems with causality, but it doesn't because we need the distance to be greater than c times the time, which means no lightspeed signal could get from A to B. If you allow ftl communication then this "escape" doesn't work anymore, and causality can be explicitly broken.
  - rogerclark 2y ago
    You can't grasp this because there is no FTL communication. Quantum entanglement does not enable FTL communication, and wormholes etc. are entirely theoretical.
    - roywiggins 2y ago
      It doesn't even enable STL communication, other than eg superdense coding and similar. But that's not what people mean when they think entanglement can be used for communication.

unsupp0rted 2y ago

For MRI / medical imaging, if nuclear wobbling can enhance signal strength, it might be possible to achieve high-quality images using lower-strength magnetic fields, and much faster. Maybe even ones that fit in a backpack and unfold.

pbhjpbhj 2y ago
For comparison, it seems the smallest portable MRI presently are ~600kg, like the Hyperfine Swoop https://hyperfine.io/swoop/overview https://hyperfine.io/swoop/overview (not affiliated).

gaze 2y ago

I’m not totally sure what makes this result so novel but also that’s probably due to my ignorance. Hyperfine qubits are pretty common using neutral atoms, and you can do imaging on the hyperfine states. Is the novelty here that the electron spin is on resonance with the nuclear spin and that it’s done with STM? I guess I don’t see how pump-probe is so much more direct than using an imaging transition.

quantadev 2y ago
I think the key thing they were pointing out was the ability to store information inside a nucleus that can be read back (reminds me of how core memory worked on the old Apollo 11 Era computers) which could be a very reliable and dense memory. It's reliable because the electron shell is sort of protecting the information stored inside the nucleus. I wonder if they'll have the same issue that core memory also had which is that by reading the magnetic state you also destroy that state, and so every bit 'read' operation has to be followed with a 'now write the bit back again' step.

acidburnNSA 2y ago

Big dream of mine would be to align nuclei of nuclear fuel atoms just so and then induce fission in such a way as to get one delayed neutron precursor and one other quick-to-stability fission product. This would allow fission power without any long-lived waste products or afterglow heat cooling challenges that dominate accident risk. Physicist friends have told me it's impossible. I've only accepted impractical for now.

AtlasBarfed 2y ago
You want an msr/LFTR and breed away the bad waste.
colechristensen 2y ago
You're thinking about the atom very classically, At the scale of the nucleus things just don't "exist" in "places". Processes are truly random and things literally don't have position/momentum/rotation/alignment until you do the thing that requires them to decide where they were and what they were doing at the time. Simpler than nuclear physics is just the electron. There is no meaningful answer to where it is around an atom at any particular time. You can either get a location or a momentum or half the information about each if you poke it, but that's just its response to being poked, it wasn't "actually" there until you poked it.
- im3w1l 2y ago
  From what I recall, quantum things have well defined states, even if those states may not correspond to position / momentum / rotation / alignment. By correctly molding the energy landscape it may be possible to set the states and state transitions up in a beneficial way for what he proposed.
  - colechristensen 2y ago
    Eh, not really. You can futz with the probability distribution, like a fast neutron will cause a different distribution of fission products than a slow one... but it is still a very random process. You can't control it like an expert at a billiards table. Especially the strong force mediated interactions between particles in the nucleus. Some people just won't believe you though.

kamalamomala 2y ago

[flagged]