What is the AdS/CFT Conjecture?

In recent years I’ve found there’s no point to trying to have an intelligible argument about “string theory”, simply because the term no longer has any well-defined meaning. At the KITP next spring, there will be a program devoted to What is String Theory?, with a website that tells us that “the precise nature of its organizational principle remains obscure.” As far as I can tell though, the problem is not one of insufficient precision, but not knowing even the general nature of such an organizational principle.

What one hears when one asks about this these days is that the field has moved on to focusing on the one part of this that is understood: the “AdS/CFT conjecture.” I’ve gotten the same answer when asking about the meaning of the “ER=EPR conjecture”, and recently the claim seems to be that the black hole information paradox is resolved, again, somehow using the “AdS/CFT conjecture.” Today I noticed this twitter thread from Jonathan Oppenheim raising questions about the “AdS/CFT conjecture” and the discussion there reminded me that I don’t understand what the people involved mean by those words. What exactly (physicist meaning of “exactly”, not mathematician meaning) is the “AdS/CFT conjecture”?

To be clear, I have tried to follow this subject since its beginnings, and at one point was pretty well aware of the exact known statements relating type IIB superstring theory on five-dim AdS space times a five-sphere with M units of flux to N=4 U(M) SYM. While this provided an impressive realization of the old dream of relating a large M QFT to a weakly coupled string theory, it bothered me that there was no meaning to the duality in the sense that no one knew how to define the strongly coupled string theory. This problem seemed to get dealt with by turning the conjecture into a definition of string theory in this background, but it was always unclear how that was supposed to work.

So, my question isn’t about that, but about the much more general use of the term to refer to all sorts of gravity/CFT relationships in various dimensions. There are hundreds if not thousands of theorists actively working on this these days, and my question is aimed at them: what exactly do you mean when you say “the AdS/CFT conjecture”?

Update: The ongoing discussion between Jonathan Oppenheim, Geoff Pennington and Andreas Karch about this on Twitter is very interesting, indicates that it isn’t so clear exactly what “the AdS/CFT conjecture” is. For me and presumably many others, would be great to have a source for an authoritative discussion of what is known about this topic. The Twitter format is very much not optimal for discussions like this.

Posted in Uncategorized | 31 Comments

Spring Course

This semester I’m teaching the second half of our graduate course on Lie groups and representations, and have started making plans for the course, which will begin next week. There’s a web-page here which I’ll be adding to as time goes on. The plan is to try and write up lecture notes for most of the course, some of which may be rewrites of older notes written when I taught earlier versions of this course. I’ll post these typically after the corresponding lectures. Any corrections or comments will be welcome.

This year I’m hoping to integrate ideas about “quantization” into the course more than in the past, starting off with the mathematics behind what physicists often call “canonical quantization”. This topic is worked out very explicitly and in great detail in this book, but in this course I’ll be giving a more stream-lined presentation from a more advanced point of view. This subject has a somewhat different flavor than usual for math graduate courses, in that instead of proving things about classes of representations, it’s one very specific representation that is the topic.

This topic is also the simplest example of the general philosophy of trying to understand Lie group representations in terms of the geometry of a “co-adjoint orbit”, and I’ll try and say a bit about this “orbit philosophy” and “geometric quantization”.

The next topic of the course will likely be more standard: the classification of finite dimensional representations of semi-simple complex Lie algebras (or, equivalently, compact Lie groups), and their construction using Verma modules. For this topic it’s hard to justify spending a lot of time writing notes, since there already are several places this has been done very well (e.g Kirillov’s book). After doing this algebraically, I’ll go back to the geometric and orbit point of view and explain the Borel-Weil-Bott theorem giving a geometric construction of these representations.

For the last part of the course, I hope to discuss the representations of SL(2,R) and the general classification of real semi-simple Lie algebras and groups. If I ever manage to understand what’s going on with the real Weil group and the Langlands classification of representations of real Lie groups, maybe I’ll say something about that, but that is probably too much to hope for.

Throughout the course, as well as the relation to quantization, I also hope to explain some things about relations to number theory. These would include the theory of theta functions early on, modular forms at the end.

Posted in Uncategorized | 5 Comments

Pierre Schapira on Récoltes et Semailles

Earlier this year I bought a copy of the recently published version of Grothendieck’s Récoltes et Semailles, and spent quite a lot of time reading it. I wrote a bit about it here, intended to write something much longer when I finished reading, but I’ve given up on that idea. At some point this past fall I stopped reading, having made it through all but 100 pages or so of the roughly 1900 total. I planned to pick it up again and finish, but haven’t managed to bring myself to do that, largely because getting to the end would mean I should write something, and the task of doing justice to this text looks far too difficult.

Récoltes et Semailles is a unique and amazing document, some of the things in it are fantastic and wonderful. Quoting myself from earlier this year

there are many beautifully written sections, capturing Grothendieck’s feeling for the beauty of the deepest ideas in mathematics. One gets to see what it looked like from the inside to a genius as he worked, often together with others, on a project that revolutionized how we think about mathematics.

A huge problem with the book is the way it was written, providing a convincing advertisement for word processors. Grothendieck seems to have not significantly edited the manuscript. When he thought of something relevant to what he had written previously, instead of editing that, he would just type away and add more material. Unclear how this could ever happen, but it would be a great service to humanity to have a competent editor put to work doing a huge rewrite of the text.

The other problem though is even more serious. The text provides deep personal insight into Grothendieck’s thinking, which is simultaneously fascinating and discouraging. His isolation and decision to concentrate on “meditation” about himself left him semi-paranoid and without anyone to engage with and help channel his remarkable intellect. It’s frustrating to read hundreds of pages about motives which consist of some tantalizing explanations of these deep mathematical ideas, embedded in endless complaints that Deligne and others didn’t properly understand and develop these ideas (or properly credit him). One keeps thinking: instead of going on like this, why didn’t he just do what he said he had planned earlier, write out an explanation of these ideas?

As an excuse for giving up on writing more myself about this, I can instead recommend Pierre Schapira’s new article at Inference, entitled A Truncated Manuscript. Schapira provides an excellent review of the book, and also explains a major problem with it. Grothendieck devotes endless pages to complaints that Zoghman Mebkhout did not get sufficient recognition for his work on the so-called Riemann-Hilbert correspondence for perverse sheaves. Mebkhout was Schapira’s student, and he explains that a correct version of the story has the ideas involved originating with Kashiwara, who was the one who should have gotten more recognition, not Mebhkout. According to Schapira, he explained what had really happened to Grothendieck, who wrote an extra twenty pages or so correcting mistaken claims in Récoltes et Semailles, but these didn’t make it into the recently published version. If someone ever gets to the project of editing Récoltes et Semailles, a good starting point would be to simply delete all of the material that Grothendieck included on this topic.

The extra pages described are available now here, as part of an extensive website called the Grothendieck Circle, now being updated by Leila Schneps. For a wealth of material concerning Grothendieck’s writings, see this site run by Mateo Carmona. It includes a transcription of Récoltes et Semailles that provides an alternative to the recently published version.

The Schapira article is a good example of some of the excellent pieces that the people at Inference have published since they started nearly ten years ago (another example relevant to Grothendieck would be Pierre Cartier’s A Country Known Only by Name from their first issue). I’ve heard news that they have lost a major part of their funding, which was reportedly from Peter Thiel and was one source of controversy about the magazine. I wrote about this here in early 2019 (also note discussion in the comments). My position then and now is that the concerns people had about the editors and funding of Inference needed to be evaluated in the context of the result, which was an unusual publication putting out some high quality articles about math and physics that would likely not have otherwise gotten written and published. I hope they manage to find alternate sources of funding that allow them to keep putting out the publication.

Posted in Uncategorized | 8 Comments

The New Yorker and the Publicity Stunt

The wormhole publicity stunt story just keeps going. Today an article about the Google Santa Barbara lab and quantum computer used in the publicity stunt appeared in the New Yorker. One of the main people profiled is Hartmut Neven, the lab founder and a publicity stunt co-author. He is described as follows:

Neven, originally from Germany, is a bald fifty-seven-year-old who belongs to the modern cast of hybridized executive-mystics. He talked of our quantum future with a blend of scientific precision and psychedelic glee. He wore a leather jacket, a loose-fitting linen shirt festooned with buttons, a pair of jeans with zippered pockets on the legs, and Velcro sneakers that looked like moon boots. “As my team knows, I never miss a single Burning Man,” he told me.

The article explains what has been going on at the Google lab under Neven’s direction:

in the past few years, in research papers published in the world’s leading scientific journals, he and his team have also unveiled a series of small, peculiar wonders: photons that bunch together in clumps; identical particles whose properties change depending on the order in which they are arranged; an exotic state of perpetually mutating matter known as a “time crystal.” “There’s literally a list of a dozen things like this, and each one is about as science fictiony as the next,” Neven said. He told me that a team led by the physicist Maria Spiropulu had used Google’s quantum computer to simulate a “holographic wormhole,” a conceptual shortcut through space-time—an achievement that recently made the cover of Nature.

There are some indications given that the wormholes aren’t everything you’d like a wormhole to be:

Google’s published scientific results in quantum computing have at times drawn scrutiny from other researchers. (One of the Nature paper’s authors called their wormhole the “smallest, crummiest wormhole you can imagine.” Spiropulu, who owns a dog named Qubit, concurred. “It’s really very crummy, for real,” she told me.) “With all these experiments, there’s still a huge debate as to what extent are we actually doing what we claim,” Scott Aaronson, a professor at the University of Texas at Austin who specializes in quantum computing, said. “You kind of have to squint.”

I took another look at the Nature article and realized that at the end it has a section explaining the contributions of each author (I’ll reproduce the whole thing as an appendix here). For Neven it has

Google’s VP Engineering, Quantum AI, H.N. coordinated project resources on behalf of the Google Quantum AI team.

Two physicists profiled are John Preskill and Alexei Kitaev. Academia in this field is seeing a big impact of quantum computing jobs and funding. According to the article:

Preskill and Kitaev teach Caltech’s introductory quantum-computing course together, and their classroom is overflowing with students. But, in 2021, Amazon announced that it was opening a large quantum-computing laboratory on Caltech’s campus. Preskill is now an Amazon Scholar; Kitaev remained with Google. The two physicists, who used to have adjacent offices, today work in separate buildings. They remain collegial, but I sensed that there were certain research topics on which they could no longer confer.

Someone told me that the Amazon lab where Preskill works has postdoc-type positions for theoretical physicists, salary about 250K.

Theoretical physics hype and quantum computing hype come together prominently in the article. Besides Shor’s algorithm and its implications for cryptography, here’s the rest of what quantum computers promise:

A quantum computer could open new frontiers in mathematics, revolutionizing our idea of what it means to “compute.” Its processing power could spur the development of new industrial chemicals, addressing the problems of climate change and food scarcity. And it could reconcile the elegant theories of Albert Einstein with the unruly microverse of particle physics, enabling discoveries about space and time.

How long until quantum computers unify GR and the Standard Model? We just need better, fault-tolerant, qubits, and then:

A thousand fault-tolerant qubits should be enough to run accurate simulations of molecular chemistry. Ten thousand fault-tolerant qubits could begin to unlock new findings in particle physics.

The hype here is far hypier than any of the string theory hype I’ve been covering over the years, and it looks like it’s got a lot more money and influence behind it, so will be a major force driving the field in coming years and decades.


The Nature contributions section is:

J.D.L. and D.J. are senior co-principal investigators of the QCCFP Consortium. J.D.L. worked on the conception of the research program, theoretical calculations, computation aspects, simulations and validations. D.J. is one of the inventors of the SYK traversable wormhole protocol. He worked on all theoretical aspects of the research and the validation of the wormhole dynamics. Graduate student D.K.K.47 worked on theoretical aspects and calculations of the chord diagrams. Graduate student S.I.D. worked on computation and simulation aspects. Graduate student A.Z.48 worked on all theory and computation aspects, the learning methods that solved the sparsification challenge, the coding of the protocol on the Sycamore and the coordination with the Google Quantum AI team. Postdoctoral scholar N.L. worked on the working group coordination aspects, meetings and workshops, and follow-up on all outstanding challenges. Google’s VP Engineering, Quantum AI, H.N. coordinated project resources on behalf of the Google Quantum AI team. M.S. is the lead principal investigator of the QCCFP Consortium Project. She conceived and proposed the on-chip traversable wormhole research program in 2018, assembled the group with the appropriate areas of expertise and worked on all aspects of the research and the manuscript together with all authors.

Update: John Horgan’s take on the stunt is Physicists Teleport Bullshit Through a Wormhole.

Update: Quanta is still actively promoting their story that

Physicists have purportedly created the first-ever wormhole, a kind of tunnel theorized in 1935 by Albert Einstein and Nathan Rosen that leads from one place to another by passing into an extra dimension of space.

with nothing on their site that indicates that this story has gotten an almost universally negative reaction from knowledgeable scientists. The one exception I’ve seen is Lubos Motl, who comments on the Quanta story. Lubos also engaged in a long exchange here with Matt Strassler. I had been worried about how Lubos was doing, it’s reassuring to see that he’s still out there, still himself, and still reliably defending the most indefensible products of string theory hype in his characteristic style.

Update: A surprising number of theorists seem willing to help hype the publicity stunt. See for instance this from Penn. It seems to me full of misinformation, for instance

Heckman: In fact, the entire experiment could have been done on a classical machine; it just would have taken a lot more time.

In fact, the “experiment” was actually done on a classical computer, in a very short amount of time. For studying this kind of model, classical computers are hugely faster and more capable than any current quantum computer. Here they were used to search for a simplified version of the real problem that was easy enough that it could be done by the quantum computer.

Update: Dan Garisto on his blog has an article about the wormhole fiasco, originally intended for publication in SciAm. Garisto explains that SciAm was originally not taken in by the publicity stunt:

I should tell you, when my editor at Scientific American sent me the embargoed press release on Thanksgiving with the subject line “Hmmm,” I responded dubiously. “They used 9 qubits! What the hell could that possibly tell you?” We chose not to cover it—initially.

He also gives a correct description of what this really was:

…the supposed bombshell dropped by the Nature paper is a calculation of an approximation of a model conjectured to be equivalent to a lower-dimensional gravity for a universe that isn’t ours. 

and challenges the misleading messaging from the scientists and from Quanta:

Quantum message discipline is sorely needed. Clarifying their headline change, Quanta noted that “The researchers behind the new work — some of the best-respected physicists in the world — frequently and consistently described their work to us as ‘creating a wormhole.’” 

When reached for comment, the study’s co-leader Maria Spiropulu pointed to a Caltech FAQ in her team’s defense. “Did we claim to have produced or observed a wormhole deformation of 3+1-dimensional spacetime?” the FAQ asks. The answer it then offers is a firm “No.” The FAQ further elaborates that what the researchers saw was only “consistent with the dynamics of a traversable wormhole.” The Nature paper is less absolute. There, Spiropulu and her co-authors describe their research as “the experimental realization of traversable wormhole dynamics on nine qubits” and discuss how they used a quantum teleportation protocol to “insert another qubit across the wormhole from right to left.” 

And in a video produced ahead of publication by Quanta, several researchers spoke gushingly, saying, “This is a wormhole” and “I think we have a wormhole, guys.” This is at best, deeply misleading.

He also has a quote from Natalie Wolchover which tries to explain the point of view which she (and others like Susskind) take that a quantum computer calculation of a toy mathematical model of a physical system is somehow really creating and doing a laboratory experiment on the physical system being modeled:

Natalie Wolchover, a Pulitzer Prize-winning science writer at Quanta, argues that when a quantum computer simulates a toy model of quantum matter, such as the SYK model, it is really “creating” the quantum system it asks about. “It’s profound but somehow I can’t put my finger on what it means about the difference between ‘real’ and ‘simulated,’” she wrote in an email.

This is complete nonsense, as Scott Aaronson tried to explain in the quote he gave for the NYT article about this:

If this experiment has brought a wormhole into actual physical existence, then a strong case could be made that you, too, bring a wormhole into actual physical existence every time you sketch one with pen and paper.

Posted in Wormhole Publicity Stunts | 29 Comments

Wormhole Publicity Stunts: Past, Present and Future

Most of the news I’m hearing today about the current wormhole publicity stunt is that physicists who could do something about it are instead blaming any problem on journalists and defending the stunt as some sort of progress forward.

I’ve been wondering what the future for this kind of thing looks like, got a partial answer by looking at this presentation today by the director of Fermilab. On page 67 she explains

Future experiments with better QC and with QCs connected through quantum networks, such as those under development at Fermilab, could provide better insight through better resolution and adding non-trivial spatial separation of the two systems.

So, next generation wormhole publicity stunts will involve, beyond going from 9 qubits to more, putting two quantum computers in two places and connecting them by a quantum network. The press reports will explain that physicists not only created a wormhole on a chip, but created a wormhole connecting two different labs.

I started looking for more information about these next-generation wormhole publicity stunts, and found instead something I hadn’t been aware of, an older such stunt, described in Towards Quantum Gravity in the Lab on Quantum Processors, which got attention last spring not at Quanta, but in the much lower profile Discover Magazine, where one reads:

The team developed quantum software that could reproduce wormhole inspired teleportation on both quantum computers and then characterized the results. “We have designed and carried out “wormhole-inspired” many-body teleportation experiments on IBM and Quantinuum quantum processors and we observe a signal consistent with the predictions,” say Shapoval and co.

One reason for the lack of significant attention to this publicity stunt as opposed to the current one surely is the decision of the authors to claim not “wormhole teleportation” but “wormhole-inspired teleportation”.

The past is the past, but it looks like the field of quantum gravity research is from now on going to be dominated by these wormhole publicity stunts, using more qubits and more quantum computers. This kind of research project is nearly ideal: you can get lots of funding from conventional sources like DOE, or even better, funding from and access to equipment at large tech companies like Google and IBM. You can convince the director of your lab or institute that you’re doing research of significance comparable to the discovery and testing of general relativity 100 years ago and your work will be vindicated by cover stories in Nature and all over the rest of the media.

Back in 1996, in The End of Science, John Horgan worried that this kind of science would end up in a “speculative post-empirical mode”, and quantum gravity theorists have for years now worried about accusations of not being connected to experiment. The solution to this problem is now clear: no one will take your wormholes seriously if they’re just on paper, so the thing to do is to get them realized in an algorithm that you run on the most twenty-first century experimental hardware available, a quantum computer in a tech company lab.

Update: There was a hoax comment posted here last night, supposedly from Natalie Wolchover, which had me fooled for a while. Whoever was doing this seems to have been making excellent use of ChatGPT, together with manipulating other aspects of how the comment was posted that helped fool me.

Posted in Wormhole Publicity Stunts | 13 Comments

Various and Sundry

If you’re sick of hearing about bogus wormholes, here are some other random topics:

  • There’s a SCOAP3 for books initiative, lots of textbooks in the field of particle physics now made open access and available here.
  • It’s completely mysterious to me why this is so, but Mochizuki’s failed proof of abc is now getting promoted at various places outside Kyoto, including Stony Brook, France (note what comes first in the suggested survey articles) and maybe even Oberwolfach.
  • One thing I’ve never understood about the dark matter story is whether just having right-handed neutrino fields (which fit very well into the pattern of fields of the Standard Model) is enough to get fundamental physics to be consistent with astrophysical observations usually interpreted as evidence of dark matter. Stacy McGaugh despises this kind of idea, where you predict particles with only gravitational interactions, making fun of it here as The Angel Particle. He has a specific agenda (modified gravity), which I think explains the vehemence.

    Ethan Siegel has an extensive discussion of gravity-only dark matter models, under the title Is dark matter’s “nightmare scenario” true?

    John Baez has a blog post on Neutrino Dark Matter, based on talking to Neil Turok about this recent paper by Boyle, Finn and Turok.

  • The National Academy has appointed an EPP-2024 committee, which has been holding various meetings. Taking a look at some of the videos, I was struck by what Lisa Randall (about 34:00-38:00 and 46:00-48:00) and Nima Arkani-Hamed (about 48:00-53:00) had to say in this one. They both emphasized the problem that it is hard for young theorists to make a career for themselves by trying to come up with a new idea, as opposed to a series of small improvements on ideas currently being pursued by many other people (often things that have been around for a long time). This I think has been a huge problem in the field for a very long time, possibly has gotten worse for some reason in recent years, and is part of the explanation for the moribund state of the subject. While they eloquently state the problem, unfortunately I don’t see much from them or anyone else about how to do something concrete to address it.
Posted in Uncategorized | 19 Comments

Publicity Stunt Fallout

Latest news this evening from Scott Aaronson at the IAS in Princeton:

Tonight, David Nirenberg, Director of the IAS and a medieval historian, gave an after-dinner speech to our workshop, centered around how auspicious it was that the workshop was being held a mere week after the momentous announcement that a wormhole had been created on a microchip (!!)—in a feat that experts were calling the first-ever laboratory investigation of quantum gravity, and a new frontier for experimental physics itself. Nirenberg speculated that, a century from today, people might look back on the wormhole achievement as today we look back on Eddington’s 1919 eclipse observations providing the evidence for general relativity.

I confess: this was the first time I felt visceral anger, rather than mere bemusement, over this wormhole affair. Before, I had implicitly assumed: no one was actually hoodwinked by this. No one really, literally believed that this little 9-qubit simulation opened up a wormhole, or helped prove the holographic nature of the real universe, or anything like that. I was wrong.

Scott has been the one person in this field I’m aware of who has tried to do something about the out-of-control hype problem that has been going from bad to worse. I do disagree with him about one thing. He goes on to write:

I don’t blame the It from Qubit community—most of which, I can report, was grinding its teeth and turning red in the face right alongside me. I don’t even blame most of the authors of the wormhole paper, such as Daniel Jafferis, who gave a perfectly sober, reasonable, technical talk at the workshop…

I do blame all those people. Unlike Scott, they’ve been either participating in hype for years, or staying quiet and enjoying the benefits of it. Grinding their teeth and turning red in the face is not enough. They need to finally say something and take action.

Update: Still unclear to me what the ultimate fallout of the publicity stunt will be. One thing that is becoming clear is that the publicity stunt is part of a vigorous and very effective campaign to mislead funding agencies and those making funding decisions. The goal is to convince them that “quantum gravity in a lab” is a real thing and the way forward for fundamental theoretical physics. The bogus Quanta story, video, headlines are not a bug, but a feature. Among the funding agencies, DOE is on board, their grant funding the publicity stunt, and they are advertising it prominently in their presentation to HEPAP today (see page 7 here). At the IAS, it seems director Nirenberg’s claims that the “first quantum gravity experiment on a chip” was possibly the biggest breakthrough in a century were not off-the-cuff comments based on what he had read in the paper or at Quanta, but prepared remarks based on conversations with IAS senior faculty. I gather that what he has been hearing from at least some of them is that the wormhole “experiment” vindicates their past research and justifies supporting them in the direction they are choosing for the future. He has though now been hearing other viewpoints.

If researchers in this field want to know what they can do about the problem, contacting places like Quanta to get them to fix their coverage is one thing, another is contacting people with funding responsibilities (ie. program officers at funding agencies, directors of institutes) who seem to have been misled by the hype campaign.

Update: Quanta hasn’t done anything more to fix the wormhole article, but they have now updated their original “Physicists have built a wormhole and successfully sent information from one end to the other.” tweet. New one reads “Experimental physicists built the mathematical analog of a wormhole inside a quantum computer by simulating a system of entangled particles.”

Update: Today at HEPAP the Fermilab director was prominently advertising the wormhole publicity stunt as a Fermilab initiative (see slide 67 here). She describes future plans for more of the same, with these calculations being performed not on one quantum computer, but on two spatially separated quantum computers connected by a quantum network. This would somehow allow for a big increase in the “quantum gravity in the lab” hype with a new Nature cover story: “FNAL scientists connect two quantum computers by a wormhole between two labs”. A question for those in the “It from Qubit” field. Are you willing to contact those responsible for funding this, who are now prominently advertising this work as a major success and new direction of research they intend to fund (e.g. Glen Crawford at DOE, and Lia Merminga at FNAL)?

Update: 4gravitons has a blogpost about the Quanta article, concentrating on the issue of “tone” of the coverage. That’s relevant for the usual problematic sort of physics coverage, but in this case something much more unusual is going on. This was a well-organized publicity stunt designed to justify funding “quantum gravity in a lab” research. Quanta was taken in more so than many other journalism venues. But the really disturbing part of this story is who else was taken in: the IAS director, the Fermilab director, the DOE division director and others, who are sophisticated consumers of science journalism, and independently getting their information from senior scientists in the field.

Posted in This Week's Hype, Wormhole Publicity Stunts | 29 Comments

The Wormhole Publicity Stunt

The best way to understand the “physicists create wormholes in the lab” nonsense of the past few days is as a publicity stunt (I should credit Andreas Karch for the idea to describe things this way), one that went too far. If the organizers of the stunt had stuck to “physicists study quantum gravity in the lab” they likely would have gotten away with it, i.e. not gotten any significant pushback.

There have already been a lot of claims about “quantum gravity in the lab” made in recent years, and surely many more will be made in the future. It’s important to understand that these all have been and always will be nothing but publicity stunts. In all cases, what is happening in these labs is some manipulation and observation of electron and electromagnetic fields at low energies. None of this has anything to do with gravitational degrees of freedom. One cannot possibly learn anything about the gravitational field or quantum gravity this way. If there is a dual theoretical description of QED in terms of a “gravitational” theory, this dual description is about other variables that have nothing to do with space-time and gravity in this world.

I’m hoping that journalists and scientists will learn something from this fiasco and not get taken in again anytime soon. It would be very helpful if both Nature and Quanta did an internal investigation of how this happened and reported the results to the public. Who were the organizers of the stunt and how did they pull it off? Already we’re hearing from Quanta that the problem was that they trusted “leading quantum gravity researchers”, and presumably Nature would make the same argument. Who were these “leading quantum gravity researchers”? Why weren’t any of the many other physicists who could have told them this was a stunt consulted?

It’s pretty clear that one of the organizers was Joe Lykken. After I wrote about his talk at CERN a month ago, someone told me that Dennis Overbye at the NYT was looking into writing about Lykken’s claims. I found it odd that the NYT would be interested in this, now it’s clear that the behind-the-scenes publicity campaign was starting already a month ago. If you look at Lykken’s slides, there’s no mention at all of the work he had done and knew was about to appear in Nature, but the whole talk is structured around arguing that such a quantum computer calculation would be a huge achievement. I still don’t know what to make of his claims in the Quanta video that the result of the Google quantum computer calculation was on a par with the Higgs discovery. Does he really believe this (he’s completely delusional) or not (he’s intentionally dishonest)?

It’s extremely unusual to not distribute a result like this on the arXiv before publication, to instead keep it confidential and go to the press with embargoed information. By doing this though you control the first wave of publicity, since you pick the press people you deal with and the terms of the embargo. One thing that first mystified me about this story is why Natalie Wolchover at Quanta was quoting comments from me on a different issue in her story, but hadn’t asked me about the article and its “physicists create wormholes in a lab” claims. One possible explanation for this is that the terms of the embargo meant she could not discuss the Nature article with me. I have to admit that if I had heard from her or any other journalist that a group was about to hold a press conference and announce publication in a major journal of claims about quantum gravity in a lab, and would I respect embargo terms so they could share info with me and get a quote, I would have said no. Likely I (and others in a similar situation) would immediately have gone and written a blog entry about how a publicity stunt was about to happen.

Update: I just noticed that the “It from Qubit” community will be gathering Monday thru Wednesday in Princeton and Thursday thru Friday in New York. One of the Princeton talks will be from one of the Nature authors (Jafferis), talking about “Emergent Gravitational Dynamics in Quantum Experiments” (no abstract, may or may not be explaining how he created the wormholes). This would be an excellent occasion I think for this community to discuss what can be done to stop publicity stunts like this one from discrediting their subject. The New York component will be invitation only, at the Simons Foundation. Presumably the Quanta people will be there to discuss with them the huge damage to their reputation they just suffered because of the publicity stunt. I’d be curious to hear how this goes from anyone participating.

Update: Something I should have linked to before is Scott Aaronson’s blog posting about this, and the comments there. One that I think is of interest explains that SYK at large N is not precisely dual to a 2d gravity theory as one often sees claimed, and has other useful explanations of issues with duality claims.

Update: According to Spiropulu on Twitter, at 2:15 Eastern Time today you can watch Jafferis talk about this stuff to a workshop at Princeton here.

Update: Just watched the livestream of the Jafferis talk. He went over in detail the paper. At the end, a few technical questions. At this point I’m seeing no evidence that anyone (other than Scott Aaronson) in this community has any problem with the outrageous hype and publicity stunts like this one being used to promote their field to the public and attract more funding.

Update: Something from Ethan Siegel, who as usual, gets it right:

There are no lessons to be learned about quantum gravity here. There are no lessons to be learned about traversable wormholes or whether they exist within our Universe. There are not even any lessons to be learned about the uniqueness or capabilities of quantum computers, as everything that was done on the quantum computer can be done and had previously (without errors!) been done on a classical computer. The best that one can take away is that the researchers, after performing elaborate calculations of the Sachdev-Ye-Kitaev model through classical means, were able to perform an analogous calculation on a quantum computer that actually returned signal, not simply quantum noise…

Wormholes and quantum computers will likely both remain topics that are incredibly interesting to physicists, and further research into the Sachdev-Ye-Kitaev model will likely continue. But the connection between wormholes and quantum computers is virtually non-existent, and this research — despite the hype — changes absolutely nothing about that fact.

To get a taste of the utter nonsense people are now getting as “News” because of this publicity stunt, try watching this ABC News segment.

Posted in This Week's Hype, Wormhole Publicity Stunts | 59 Comments

Igor Krichever 1950-2022

I just heard the sad news that Igor Krichever passed away this morning at the age of 72. Igor was a great scholar, a wise man, and a wonderful human being. He will be sorely missed by his colleagues at Columbia and elsewhere. My condolences to his family, which includes another first-rate mathematician, his son-in-law Sasha Braverman. During the past year Igor had been suffering from a progressive neuro-degenerative disease. Fortunately he was still in good enough health to fully participate in and enjoy his 70th birthday conference, which took place at Columbia in early October.

In recent years Igor had been spending only one semester each year at Columbia, much of the rest of the time was in Moscow, where he was director of Skoltech’s Center for Advanced Studies. He came to Columbia in the mid-90s, with his hiring the beginning of a period of successful expansion and improvement in the math department. He was a gentle and friendly person, and it was always a pleasure to have a chance to talk to him about one topic or another. When he became chair of the department I remember thinking that it seemed unlikely that someone as scholarly and laid-back as him, with a somewhat typical Russian mathematician’s other-worldliness, could deal well with the challenges of the university bureaucracy. I was very, very wrong, as it became clear that he was extremely wise in the ways of the world and a great department chair. I guess that after growing up with Soviet bureaucracy, dealing with the Columbia version was child’s play.

Igor was a very distinguished mathematician, one of the leading figures working at the intersection of integrable systems and algebraic geometry. For more about his scientific work, there’s a biographical notice written by some of his colleagues at the time of his 60th birthday (which was also celebrated at Columbia with a conference, see here).

Posted in Obituaries | 2 Comments

This Week’s Hype

This morning Quanta Magazine informs us that Physicists Create a Wormhole Using a Quantum Computer, promoting the article on Twitter with BREAKING: Physicists have built a wormhole and successfully sent information from one end to the other and Physicists have used Google’s quantum computer to send a signal through a wormhole, a shortcut in space-time first theorized by Einstein and Rosen in 1935.

This work is getting the full-press promotional package: no preprint on the arXiv (unless I’m missing something?), embargoed info to journalists, with reveal at a press conference, a cover story in Nature, accompanied by a barrage of press releases (see here, here, here, with Harvard, MIT and Google to come). This is the kind of PR effort for a physics result I’ve only seen before for things like the Higgs and LIGO gravitational wave discoveries (OK, and the primordial gravitational wave non-discovery). It would be appropriate I suppose if someone actually had built a wormhole in a lab and teleported information through it, as advertised.

An additional part of the package is the Quanta coverage, with a very long article by Natalie Wolchover and an over-the-top seventeen minute film How Physicists Created a Wormhole in a Quantum Computer, with abstract

Almost a century ago, Albert Einstein realized that the equations of general relativity could produce wormholes. But it would take a number of theoretical leaps and a “crazy” team of experimentalists to build one on Google’s quantum computer.

The two senior physicists behind this, Joe Lykken and Maria Spiropulu, have histories that go way back of successfully promoting to the press nonsense about exotic space-time structures appearing in experiments that have nothing to do with them. Back in 1999, the New York Times published Physicists Finally Find a Way to Test Superstring theory, which featured Joe Lykken. In 2003, they featured Maria Spiropulu explaining how she was going to find extra dimensions (or “something just as ‘crazy””) at the Tevatron, or failing that, the LHC.

I just saw that the New York Times also has a big story about this: Physicists Create ‘the Smallest, Crummiest Wormhole You Can Imagine’. At least this article has some sensible skeptical quotes, including:

“The most important thing I’d want New York Times readers to understand is this,” Scott Aaronson, a quantum computing expert at the University of Texas in Austin, wrote in an email. “If this experiment has brought a wormhole into actual physical existence, then a strong case could be made that you, too, bring a wormhole into actual physical existence every time you sketch one with pen and paper.”

An odd thing about the Quanta article is that it contains a couple quotes from me, that aren’t at all about the wormhole business. They’re about the attempt to use AdS/CFT to either solve QCD or get a viable theory of quantum gravity. Back in June Wolchover contacted me with some questions about AdS/CFT. It seems that she was planning a long piece on AdS/CFT, one which somehow many months later got amalgamated with the wormhole nonsense. I had forgotten that I was thinking of turning what I sent her back then into a blog posting but never got around to it, so just earlier today posted it here.

On the substance of what is really going on here, it’s exactly the same as what was discussed extensively a month ago in this posting and in its comment section. The claim that “Physicists Create a Wormhole” is just complete bullshit, with the huge campaign to mislead the public about this a disgrace, highly unhelpful for the credibility of physics research in particular and science in general.

Update: Here’s the promotional piece from Google, and Will Kinney’s reaction.

Update: Physics World has Quantum teleportation opens a ‘wormhole in spacetime’ with a quote from Witten saying positive things about this experiment (“a ‘milestone’ in developing control over microscopic quantum systems”), nothing about the wormholes.

Update: I tried reading the paper in some more detail. Almost all the calculations in the paper were done on paper or on a classical computer. As far as I can tell, all they did was perform elaborate SYK calculations on a classical computer, together with simulations of noise on the Google quantum computer, trying to find a possible calculation on the quantum computer that would have signal, not just noise. Once such an N=7 SYK calculation was identified, they used a 9 qubit quantum computer and the noisy result matched the simulation result from the classical computer, exactly as expected. Seeing the completely expected match between results from a 9 bit noisy quantum computer and the results of the simulation of this on a classical computer caused Maria Spiropulu to say that “I was shaken” and “It was nuts. It was nuts”, while Joe Lykken felt that the moment was on a par with discovery of the Higgs particle.

I hadn’t noticed that the Nature issue comes with an article by Brown and Susskind, A holographic wormhole traversed in a quantum computer. Amidst the hype, they do at least point out:

because nine qubits can be easily simulated on a classical computer, the results of this experiment cannot teach us anything that could not be learnt from a classical computation, and will not teach us anything new about quantum gravity.

New Scientist is the sober one here, with their headline the relatively reasonable A quantum computer has simulated a wormhole for the first time

Update: MSN is going for the larger context: physicists didn’t just create a wormhole in a lab, also This tiny 2D wormhole could finally solve the biggest problem in physics

Update: Andreas Karch on Twitter I think has an accurate characterization of this “mostly a publicity stunt”:

Experimentally it’s of course cool they can do SYK – as a demonstration they have control over their device. They can couple 9 qbits in a pre-specified way. But I guess we knew they could do this before. Going after SYK in particular, in my mind, is mostly a publicity stunt.

Update: Quanta has changed the title of their article from “Physicists Create a Wormhole” to “Physicists Create a Holographic Wormhole”.

The MIT press release is out, and it’s comical in the other direction, explaining the huge breakthrough as MIT researchers use quantum computing to observe entanglement.

Chad Orzel is getting flashbacks to 2006, which I can well understand. Many of the worst offenders in this hype campaign were hard at work doing the same thing back then (and earlier), and I was, as now, ineffectually trying to do something about it (the first edition of “This Week’s Hype” dates back to that year).

Update: Quanta has also deleted the original “BREAKING: Physicists have built a wormhole and successfully sent information from one end to the other” tweet. Davide Castelvecchi at Nature as a more sober story, ending with

The theory tested at the Google lab “only has a very tangential relationship to any possible theories of quantum gravity in our Universe”, says Peter Shor, a mathematician at the Massachusetts Institute of Technology in Cambridge.

Update: More coverage of this here, here, here and here. Quanta and Wolchover are, quite appropriately, blaming the “some of the best-respected physicists in the world” who sold them this nonsense, see here, here and here.

Posted in This Week's Hype, Wormhole Publicity Stunts | 37 Comments