Quanta has an article out today about the wormhole publicity stunt, which sticks to the story that by doing a simple SYK model calculation on a quantum computer instead of a classical computer, one is doing quantum gravity in the lab, producing a traversable wormhole and sending information through it. From what I’ve heard, the consensus among theorists is that the earlier Quanta article and video were nonsense, outrageously overhyping a simulation and then bizarrely identifying a simulation with reality if it’s done on a quantum computer.
The new article is just about as hype-laden, starting off with:
A holographic wormhole would scramble information in one place and reassemble it in another. The process is not unlike watching a butterfly being torn apart by a hurricane in Houston, only to see an identical butterfly pop out of a typhoon in Tokyo.
In January 2022, a small team of physicists watched breathlessly as data streamed out of Google’s quantum computer, Sycamore. A sharp peak indicated that their experiment had succeeded. They had mixed one unit of quantum information into what amounted to a wispy cloud of particles and watched it emerge from a linked cloud. It was like seeing an egg scramble itself in one bowl and unscramble itself in another.
In several key ways, the event closely resembled a familiar movie scenario: a spacecraft enters one black hole — apparently going to its doom — only to pop out of another black hole somewhere else entirely. Wormholes, as these theoretical pathways are called, are a quintessentially gravitational phenomenon. There were theoretical reasons to believe that the qubit had traveled through a quantum system behaving exactly like a wormhole — a so-called holographic wormhole — and that’s what the researchers concluded.
An embarrassing development provides the ostensible reason for the new article, the news that “another group suggests that’s not quite what happened”. This refers to this preprint, which argues that the way the Jafferis-Lykken-Spiropulu group dramatically simplified the calculation to make it doable on a quantum computer threw out the baby with the bathwater, so was not meaningful. The new Quanta piece has no quotes from experts about the details of what’s at issue. All one finds is the news that the preprint has been submitted to Nature and that
the Jafferis, Lykken and Spiropulu group will likely have a chance to respond.
There’s also an odd piece of identity-free and detail-free reporting that
five independent experts familiar with holography consulted for this article agreed that the new analysis seriously challenges the experiment’s gravitational interpretation.
I take all this to mean that the author couldn’t find anyone willing to say anything in defense of the Nature article. An interesting question this raises is that if all experts agree the Nature article was wrong, will it be retracted? Will the retraction also be a cover story?
The update of the original story is framed by enthusiastic and detailed coverage of the work of Hrant Gharibyan on similar wormhole calculations. The theme is that while Jafferis-Lykken-Spiropulu may have hit a bump in the road, claiming to be doing “quantum gravity in the lab” by SYK model calculations on quantum computers is the way forward for fundamental theoretical physics:
The holographic future may not be here yet. But physicists in the field still believe it’s coming, and they say that they’re learning important lessons from the Sycamore experiment and the ensuing discussion.
First, they expect that showing successful gravitational teleportation won’t be as cut and dry as checking the box of perfect size winding. At the very least, future experiments will also need to prove that their models preserve the chaotic scrambling of gravity and pass other tests, as physicists will want to make sure they’re working with a real Category 5 qubit hurricane and not just a leaf blower. And getting closer to the ideal benchmark of triple-digit numbers of particles on each side will make a more convincing case that the experiment is working with billowing clouds and not questionably thin vapors.
No one expects today’s rudimentary quantum computers to be up to the challenge of the punishingly long Hamiltonians required to simulate the real deal. But now is the time to start chiseling away at them bit by bit, Gharibyan believes, in preparation for the arrival of more capable machines. He expects that some might try machine learning again, this time perhaps rewarding the algorithm when it returns chaotically scrambling, non-commuting Hamiltonians and penalizing it when it doesn’t. Of the resulting models, any that still have perfect size winding and pass other checks will become the benchmark models to drive the development of new quantum hardware.
If quantum computers grow while holographic Hamiltonians shrink, perhaps they will someday meet in the middle. Then physicists will be able to run experiments in the lab that reveal the incalculable behavior of their favorite models of quantum gravity.
“I’m optimistic about where this is going,” Gharibyan said.
I had thought that perhaps this fiasco would cause the Quanta editors to think twice, talk to skeptical experts, and re-report the original credulous story/video. Instead, it looks like their plan is to double down on the “quantum gravity in the lab” hype.
Update: Two more related pieces of wormhole news.
- On Friday Harvard will be hosting a talk on the non-wormhole.
- In this preprint Maldacena argues for another example of how to do quantum gravity in the lab, by doing a QM calculation on a quantum computer that will “have created something that behaves as a black hole in the laboratory” (no wormholes, just black holes). The calculation he suggests involves not the newer SYK model, but the ancient BFSS matrix model from 27 years ago, which at the time got a lot of attention as a possible definition of M-theory.
Update: The Harvard CMSA talk about the wormholes is available here. I didn’t see anything in the slides about the Yao et al. criticism of this work. In the last minute of the video there was a question about this, and some reference to the criticism having been addressed during the talk. Supposedly there was some quick verbal summary of this response to the criticism in this last minute, but the sound was so garbled I couldn’t understand it. Here’s the automatically generated transcript:
so I guess I guess um we’re talking about like at the time of interpretation you do see this
operating ghost in kind of declare the two-point function if you’re looking for at later times you can ask about
different kind of scenarios one is accepting the single-sided systems what it’s doing it’s like internal reversible
verbal hamiltonian and you see thermalizing Dynamics in the library
um perhaps also the size winding uh although it’s not necessarily required
for all of your fermions to show size winding because you have done gravitational attractions in your model we do see impact that all the pronouns
have quite good size winding they’re good enough to allow them to teleport to size binding but the time and size
binding is clearly related to like the the rate of Decay the two-point function and so it seems to actually lend itself
to an even tighter kind of interpretation where would you associate different masses through different
permeons and this is quite consistent that is
Someone with more patience and interest in this perhaps can carefully follow the talk and report what the response to the Yao et al. criticism actually was.
Update: A response by the original authors to Yao et al. has been posted as “Comment on “Comment on “Traversable wormhole dynamics on a quantum processor” ” “. From the abstract, the claim seems to be that the results of the toy model calculation are “consistent with a gravitational interpretation of the teleportation dynamics, as opposed to the late-time dynamics”, and that this is not in conflict with the objections by Yao et al. These objections are described as “counterfactual scenarios outside of the experimentally implemented protocol.” The odd thing here is the description of the quantum computer calculation as a “factual” experimental result, part of an “experimentally implemented protocol”. The quantum computer calculation was not an experiment but a calculation, with a known-in-advance result (the calculation done previously on a classical computer). The criticisms of Yao et al. aren’t “counterfactual” to an experimental protocol, but challenging the interpretation of a calculation. As far as I can tell, this whole discussion is about how to interpret simple calculations you can do on any conventional computer, nothing to do with an “experiment”.