New Results in Quantum Tunneling vs. The Speed of Light

Paradoxically, the most promising prospects for moving matter around faster than light may be to put a metaphorical brick wall in its way. New efforts in quantum tunneling - both theory and experiment - show that superluminal motion may be possible, while still managing to avoid the paradox of superluminal signaling.Paradoxically, the most promising prospects for moving matter around faster than light may be to put a metaphorical brick wall in its way. New efforts in quantum tunneling - both theory and experiment - show that superluminal motion may be possible, while still managing to avoid the paradox of superluminal signaling.

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Watch our original Quantum Tunneling episode here:

Relativistic Tunneling Paper

Nature Paper

Hosted by Matt O'Dowd
Written by Tom Rivlin & Matt O'Dowd
Post-Production by Leonardo Scholzer, Yago Ballarini, Pedro Osinski, Adriano Leal & Stephanie Faria
GFX Visualizations: Ajay Manuel
Directed by Andrew Kornhaber
Assistant Producer: Setare Gholipour
Executive Producers: Eric Brown & Andrew Kornhaber

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[danieljensen]

That feel when causality is only highly statistically likely.

[FiksIIanzO]

Bug report:
Subatomic particles sometimes phase out of bounds when players aren't looking. Maybe something to do with cheaper collision logic while they're culled?
---
//It's a long standing legacy code issue. Someone thought it was a good idea to dynamically separate particles based on a physics bug instead of a timer so that stars work properly, and now too much of the project is built upon this little bodge. It's a headache, but the project is long in release and we would have to refactor good half of subatomic scripts to fix that, and I know how many issues will come out of that, so let's just pretend it's a feature and be dome with it. Next universe, I'm firing anyone who even suggests subatomic interactions. PS: If you think this is weird, check out black hole code. Not even I understand why they shrink constantly. -G.

[MarkArandjus]

In the true spirit of physics the animator just averaged that car into a sphere :D

[Snwar]

the inverse effect of quantum tunneling is also pretty insane: there is a chance that a particle gets deflected by a potential barrier despite having enough energy to (in the classical case ALWAYS) pass over it

[tbatlas]

The universe saves CPU space by not fully rendering particles that aren't being viewed by the player. This leads to entities sometimes glitching through walls.

[Sponzibobu]

Oh my god, I remember back in college, when I was in a introductory physics class learning about the Heisenberg's Uncertainty Principle, another student asked if FTL teleportation was possible due to the uncertainty of a particle's position. I did not think much about the question at all, but this video makes me wonder if the person who asked that question back then is a true genius! It's amazing how seemingly random curiosities can actually be profound physics mysteries!

[farfa]

Can it be considered a travel at all? My understanding has always been that the particle just chooses to now exist over there; so no distance is ever traveled, faster or slower than light.

[Taqu]

I find this tunneling narrative a bit misleading. We don't talk about localized particles here, a part of the particle's wavefunction was always at the observation point to begin with. It is a matter of statics to be able to spot the particle at a distant location far from where its wavefunction peaks. Therefore "particle's" wavefunction does not necessarily travel in space for tunneling to occur.

[meerjt]

This is one situation where actually looking at and trying to understand the equations is extremely helpful. The moment I understood why the barrier having a higher energy than the particle caused the probability to flip from a sine wave into an exponential decay still my favourite moment in physics study

[bustedrav]

Reminds me of the quote "no matter where you go, there you are" if the wave propogates to the other side of the barrier and the particle ends up there, did the particle really "travel" at all?

[vampyricon]

Late comment but hopefully this is in time: I asked around for other grad students' opinions of the paper, at least the one with the Dirac equation, and they told me that the solution is unphysical precisely because of the acausal propagators. They told me quantum field theory was developed in part because relativistic single-particle quantum mechanics still contains unphysical dynamics such as superluminal tunnelling, and that the results are unlikely to hold up in the full QFT treatment.

I've also seen the experimental paper around the time it was published and (iirc) noticed that they used the Schroedinger equation rather than a relativistic treatment. Extrapolating from that to superluminal tunnelling is like claiming that a constant acceleration can accelerate something to superluminal speeds.

I asked because I thought the argument that this acausality doesn't matter to be extremely flimsy: One only needs to send a number of particles on the order of 1/(tunnelling probability) to send a superluminal signal.

[sebastienpaquin]

This makes me think a weird thought, could a particle still tunnel trough "something", even if "something" isn't actually there? IE, does it really NEED something in the way to tunnel trough? In fact, do particles even "travel" at all, or do their wave function just more or less randomly tunnel about every which way, and their path calculated by the Schrodinger equation just the averaging out of all this "(co)motion"?
In short, if a particle tunnels trough a forest and there was no tree in the way, did it tunnel at all, or just traversed it?

[herbivoretarleck]

Does a black hole event horizon qualify as one of those seemingly impenetrable barriers through which a quantum particle could tunnel?

[evelienheerens]

I'm not sold on the hidden premise that there is a 'tunneling event'. The tunneling seems to not so much take place as an event rather then as an effect. To have it occur as an event, we would have to observe what happens between the moment we launch the particle and the moment the wave function collapses. For that to happen, we would have to observe it while in wave function and since observation collapses the wave function this is impossible. You'd have to observe it before it's observed.

This in turn makes the idea of speed meaningless, all we have is the distance between events, there is no path traversed.

I suspect this will turn out like quantum entanglement, not suitable to send messages.

Have you ever seen a lightning strike filmed with a high speed camera? First the lightning bolt arcs along many increasingly branching paths, until one of those paths touches the ground and the others disappear, leaving only the path that found it's way being followed. That's what I used to imagine quantum tunneling to look like, every path being followed until the correct one is found and the others are abandoned for the correct one. What if that is exactly what happens to a particle only instead of traveling in only 3 dimensions it travels in 3+x dimensions and the barrier doesn't obstruct the path in all of them?

[Bdix]

What's funny is that I'm watching this while procrastinating characterizing wafers that will be used to make tunnel diodes. This video has certainly slowed the tunneling process.

[karlwaugh]

It seems like single "quantum bits" of data could travel FTL, but that there is some statistical aspect of non-FTL and so the law of light speed becomes similar to things like the 2nd law of thermodynamics which is statical in nature. Does this make it stronger? Does it point to a relatively/QM cross over having some form of statistical nature?

[ziguirayou]

So in conclusion, FTL travel should be accomplished by the IID (Infinite Improbability Drive).
Doug Adams was right again. In your face Albert!

[stapuft]

PLEASE, PLEASE, PLEASE, do a video on the "flexibility" of time, for example the "delayed double slit experiment", where the "observer" is so far away from the experiment that by the time they actually observe it, the experiment is long over, YET, the fact that they observed it STILL has an impact on the outcome of the experiment, even though it happens AFTER the results, instead of before/during, like in the normal double slit experiment.

[Gorlokki]

It's 4am, I can't sleep and I'm super pumped watching this :)

[Censorededs]

I think the best joke was "FTL Verified? Not so fast."