Raymond Laflamme (1960-2025)
Even with everything happening in the Middle East right now, even with (relatedly) everything happening in my own family (my wife and son sheltering in Tel Aviv as Iranian missiles rained down), even with all the rather ill-timed travel I’ve found myself doing as these events unfolded (Ecuador and the Galapagos and now STOC’2025 in Prague) … there’s been another thing, a huge one, weighing on my soul.
Ray Laflamme played a major role in launching the whole field of quantum computing and information, and also a major role in launching my own career. The world has lost him too soon. I’ve lost him too soon.
After growing up in Quebec—I still hear his French-Canadian accent, constantly on the verge of laughter, as I’m writing this—Ray went into physics and became a PhD student of Stephen Hawking. No, not a different Stephen Hawking. If you’ve read or watched anything by or about Hawking, including A Brief History of Time, you might remember the story where Hawking believed for a while that time would reverse itself as the universe contracted in a Big Crunch, with omelettes unscrambling themselves, old people turning into children, etc. etc., but then two graduate students persuaded him that that was totally wrong, and entropy would continue to increase like normal. Anyway, Ray was one of those students (Don Page was the other). I’d always meant to ask Ray to explain what argument changed Hawking’s mind, since the idea of entropy decreasing during contraction just seemed obviously wrong to me! Only today, while writing this post, did I find a 1993 paper by Hawking, Laflamme, and Lyons that explains the matter perfectly clearly, including three fallacious intuitions that Hawking had previously held. (Even though, as they comment, “the anatomy of error is not ruled by logic.”)
Anyway, in the mid-1990s, starting at Los Alamos National Lab and continuing at the University of Waterloo, Ray became a pioneer of the then-new field of quantum computing and information. In 1997, he was a coauthor of one of the seminal original papers that proved the possibility of fault-tolerant quantum computation with a constant error rate, what we now call the Threshold Theorem (Aharonov and Ben-Or had such a result independently). He made lots of other key early contributions to the theory of quantum error-correcting codes and fault-tolerance.
When it comes to Ray’s scientific achievements after his cosmology work with Hawking and after quantum fault-tolerance—well, there are many, but let me talk about two. Perhaps the biggest is the KLM (Knill-Laflamme-Milburn) Theorem. It would be fair to say that KLM started the entire field of optical or photonic quantum computation, as it’s existed in the 21st century. In one sentence, what KLM showed is that it’s possible to build a universal quantum computer using only
- identical single-photon states,
- a network of “linear-optical elements” (that is, beamsplitters and phaseshifters) that the photons travel through, and
- feedforward measurements—that is, measurements of an optical mode that tell you how many photons are there, in such a way that you can condition (using a classical computer) which optical elements to apply next on the outcome of the measurement.
All of a sudden, there was a viable path to building a quantum computer out of photons, where you wouldn’t need to get pairs of photons to interact with each other, which had previously been the central sticking point. The key insight was that feedforward measurements, combined with the statistical properties of identical bosons (what the photons are), are enough to simulate the effect of two-photon interactions.
Have you heard of PsiQuantum, the startup in Palo Alto with a $6 billion valuation and hundreds of employees that’s right now trying to build an optical quantum computer with a million qubits? Or Xanadu, its competitor in Toronto? These, in some sense, are companies that grew out of a theorem: specifically the KLM Theorem.
For me, though, the significance of KLM goes beyond the practical. In 2011, I used the KLM Theorem, together with the fact (known since the 1950s) that photonic amplitudes are the permanents of matrices, to give a new proof of Leslie Valiant’s celebrated 1979 theorem that calculating the permanent is a #P-complete problem. Thus, as I pointed out in a talk two years ago at Ray’s COVID-delayed 60th birthday conference, entitled Ray Laflamme, Complexity Theorist (?!), KLM had said something new about computational complexity, without any intention of doing so. More generally, KLM was crucial backdrop to my and Alex Arkhipov’s later work on BosonSampling, where we gave strong evidence that some classical computational hardness—albeit probably not universal quantum computation—remains in linear optics, even if one gets rid of KLM’s feedforward measurements.
(Incidentally, I gave my talk at Ray’s birthday conference by Zoom, as I had a conflicting engagement. I’m now sad about that: had I known that that would’ve been my last chance to see Ray, I would’ve cancelled any other plans.)
The second achievement of Ray’s that I wanted to mention was his 1998 creation, again with his frequent collaborator Manny Knill, of the One Clean Qubit or “DQC1” model of quantum computation. In this model, you get to apply an arbitrary sequence of 2-qubit unitary gates, followed by measurements at the end, just like in standard quantum computing—but the catch is that the initial state consists of just a single qubit in the state |0⟩, and all other qubits in the maximally mixed state. If all qubits started in the maximally mixed state, then nothing would ever happen, because the maximally mixed state is left invariant by all unitary transformations. So it would stand to reason that, if all but one of the qubits start out maximally mixed, then almost nothing happens. The big surprise is that this is wrong. Instead you get a model that, while probably not universal for quantum computation, can do a variety of things in polynomial time that we don’t know how to do classically, including estimating the traces of exponentially large unitary matrices and the Jones polynomials of trace closures of braids (indeed, both of these problems turn out to be DQC1-complete). The discovery of DQC1 was one of the first indications that there’s substructure within BQP. Since then, the DQC1 model has turned up again and again in seemingly unrelated investigations in quantum complexity theory—way more than you’d have any right to expect a priori.
Beyond his direct contributions to quantum information, Ray will be remembered as one of the great institution-builders of our field. He directed the Institute for Quantum Computing (IQC) at the University of Waterloo in Canada, from its founding in 2002 until he finally stepped down in 2017. This includes the years 2005-2007, when I was a postdoc at IQC—two of the most pivotal years of my life, when I first drove a car and went out on dates (neither of which I do any longer, for different reasons…), when I started this blog, when I worked on quantum money and learnability of quantum states and much more, and when I taught the course that turned into my book Quantum Computing Since Democritus. I fondly remember Ray, as my “boss,” showing me every possible kindness. He even personally attended the Quantum Computing Since Democritus lectures, which is why he appears as a character in the book.
As if that wasn’t enough, Ray also directed the quantum information program of the Canadian Institute for Advanced Research (CIFAR). If you ever wondered why Canada, as a nation, has punched so far above its weight in quantum computing and information for the past quarter-century—Ray Laflamme is part of the answer.
At the same time, if you imagine the stereotypical blankfaced university administrator, who thinks and talks only in generalities and platitudes (“how can we establish public-private partnerships to build a 21st-century quantum workforce?”) … well, Ray was whatever is the diametric opposite of that. Despite all his responsibilities, Ray never stopped being a mensch, a friend, an intellectually curious scientist, a truth-teller, and a jokester. Whenever he and I talked, probably at least a third of the conversation was raucous laughter.
I knew that Ray had spent many years battling cancer. I naïvely thought he was winning, or had won. But as so often with cancer, it looks like the victory was only temporary. I miss him already. He was a ray of light in the world—a ray that sparkles, illuminates, and as we now know, even has the latent power of universal quantum computation.
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Comment #1 June 24th, 2025 at 12:31 am
Dear Scott,
Thank you for this beautiful memorial for Ray.
This is Dawei Lu from Southern University of Science and Technology (SUSTech). I was Ray’s postdoc from 2012 to 2017, during which I learned so much from him. Ray was undoubtedly the most noble person I have ever met. I was completely shocked when I received the news of his passing.
I still vividly remember the celebration two years ago for Ray’s 60th birthday (although it was postponed by a couple of years due to COVID). That evening, he was so radiant and full of life, sharing old stories and expressing how proud he was of all his students and postdocs at the Perimeter Institute. I truly thought he had beaten cancer. He was always so kind, humorous, and optimistic that you could never see a single shadow on his face.
I also remember clearly the first day he “interviewed” me at RAC. He said, “I am happy with you, and I hope you are happy with us.” It was such a lovely day, and I can still see the bright ray of light on Ray’s face — that moment remains my most cherished memory of him.
I felt deep sorrow when I heard the news — I truly wished it were not true. Thank you for writing this tribute to Ray. He really was a true ray of light for all of us.
God bless him. May the ray always be with him.
Best,
Dawei
Comment #2 June 24th, 2025 at 6:13 am
I’m sorry for the loss to the QC and broader scientific community. It’s Aaronson’s blog, so he can write what he wants, but I know that I’m far from the only one who would like to see a lot more posts like this related to QC and a whole lot less about politics, about which the gulf in moral intuitions is too vast to have a reasonable conversation.
Comment #3 June 24th, 2025 at 6:23 am
What a wonderful tribute.
Comment #4 June 24th, 2025 at 8:44 am
Thanks for the piece, Scott. May Ray rest in peace.
It’s so sad to see so many people I knew taken away too soon by cancer. Perhaps a bit annoying on my side to say in this context, but I wish we (as a society) would give things like the following more visibility which could help with the cancer epidemic.
Comment #5 June 24th, 2025 at 9:12 am
How sad! And I can assure those that didn’t know Raymond that there is no hyperbole in Scott’s tribute. I was a postdoc with him at Los Alamos and his colleague for many years at Perimeter, so I knew him well. Scott also completely skipped over Raymond’s pivot to be an experimentalist. He was one of the pioneers of NMR quantum computing, which for a while had the largest and most accurate quantum computers, albeit very serious scaling challenges.
Raymond had many great anecdotes. One of my favorites is from his time as Stephen Hawking’s student, when one of his tasks was to go through Hawking’s no-doubt voluminous mail from the public. As you might imagine, a certain number of these were from … let us call them amateur scientists, who had their own original theories of the universe. At one point, Raymond decided to tell two of these amateurs that Prof. Hawking was not able to correspond with them but suggested that the two talk to each other. After a while, he got a response from one of the two, who said, “Why did you ask me to talk to that guy? He’s crazy!”
Comment #6 June 24th, 2025 at 9:53 am
Del #4
It’s definitely interesting and worth considering, but, when it comes to cancer, there’s nothing that truly “kills” cancer, unless your cancer is one of the few that’s really very susceptible to a magic bullet.
At best there are various strategies to slow it down.
Everyone’s different too, and every cancer is different too.
I wouldn’t be surprised if some research would show that “fasting” can also be sometimes a trigger for cancer growth in many people (for the simple reason that, when fasting, many people unknowingly put themselves in a state of malnutrition). Obviously obesity isn’t good either, but Dr Laflamme looked pretty fit on that picture Scott posted.
I’ve been living with two different cancers (one stage 4 and one stage 3) for over 10 years, and my oncologist’s advice to me is “Keep doing whatever you’re doing!”… I’m doing a lot of things, but fasting ain’t one of them… I was actually fasting for over a year when my whole cancer “ordeal” started, of course it’s impossible to know whether it mattered, haha.
Comment #7 June 24th, 2025 at 9:56 am
Thank you for this wonderful tribute. Laflamme has indeed been a scientific inspiration in Canada, and his is a truly important legacy. Ours is a small country, and the work of intellectual giants like Laflamme has a big positive impact.
Comment #8 June 24th, 2025 at 10:01 am
Forgot to mention that a good friend of mine has been eating a single meal a day for most of his life, just by habit, and he was always very fit without even trying.
But that didn’t prevent him from getting a devastating stage 3 colon/rectal cancer in his early 50s.
After a few years he’s okay now, and still eating just once a day.
Comment #9 June 24th, 2025 at 10:52 am
Hi Scott,
I’m so sorry for your and the entire quantum community’s terrible loss. While I never met him, ending my academic journey only finishing my undergrad in mathematics, his having you on as a postdoc Les me to finding this blog and your book. I met you once, when you were visiting for a guest lecture, and accompanied the group to bubble tea after where you were scoping out candidates for scholarly work, and if he was as entertaining and welcoming as you were, I am sad he is gone.
I hope your family is safe. I now have a girlfriend who has relatives in Israel, which obviously brings the matter closer to home, though the conflicts divide her family as well. As she would say to me, any time I mention a late family member or friend, may his memory be a blessing.
Stay safe in these dangerous times.
Comment #10 June 24th, 2025 at 10:57 am
Is there any evidence that an experimental implementation of the “one clean qubit” model might be practical useful for (probably non-universal) quantum computation, at least in the sense of “beyond today’s actual real-world classical computers”? It seems to me that an initial state of one clean qubit and many maximally mixed qubits might be easier to prepare experimentally than a pure state of many qubits.
But on the other hand, I assume that while you can allow most of your qubits to fully decohere before you start your computation within this model, once you start the computation you need to prevent any additional external entanglement with the environment just as usual. And my understanding is that state preparation is rarely the practical implementation bottleneck for today’s quantum computers. So my guess is that implementing this model experimentally is probably 99.99% as hard as implementing traditional quantum computers, for a less powerful payoff – so not useful in practice.
Comment #11 June 24th, 2025 at 11:10 am
Daniel Gottesman #5:
Scott also completely skipped over Raymond’s pivot to be an experimentalist. He was one of the pioneers of NMR quantum computing, which for a while had the largest and most accurate quantum computers, albeit very serious scaling challenges.
Yeah, you’re right, I shouldn’t have skipped that! Even though liquid NMR ended up being sort of a dead end, it was indeed historically important as the first experimental proof-of-concept. Anyone who knows more about Ray’s experimental contributions is welcome to write more here.
Comment #12 June 24th, 2025 at 11:27 am
CB #2:
It’s Aaronson’s blog, so he can write what he wants, but I know that I’m far from the only one who would like to see a lot more posts like this related to QC and a whole lot less about politics, about which the gulf in moral intuitions is too vast to have a reasonable conversation.
You’re absolutely correct, in the sense that if I wrote more about QC and less about politics, I’d be happier and most of readers would also be happier.
It’s just … become really hard these past couple years. After all, what you call “politics” really means the universities where I spend most of my life, plus cities all over the world, plus social media, plus an entire younger generation, getting conquered by militant activists whose position, stripped of nuances and caveats and complexities, is basically that my family members are illegitimate settler-colonists who deserve to be murdered. (“What did y’all think decolonization meant? vibes? papers? essays?”) For the first time in my life, I’ve lost a significant number of friends, because, well … am I supposed to remain friendly with people who believe that?
And who’s fighting those activists? A different militant faction, which controls the Presidency and Congress of the United States … and which happens to be right now gleefully smashing the entire academic science bubble where I live and work, considering it a citadel of the hated liberal elite. And doing incomprehensible amounts of other damage to the world besides.
So, trapped between these two fanaticisms, both of them burning down much of what I value most on this earth, I’ve found that it’s really, really hard to pretend even temporarily that (let’s say) QMA vs. QCMA or efficiently verifiable quantum supremacy is the most important problem in the world … as I’d need to do to work productively on those problems, or even usually to blog about them.
Again, though, you’re 100% right: if I could pretend that, as I did for example during my years in Waterloo when I joked around every week with Ray Laflamme, I’d be happier and more productive! Any advice?
Comment #13 June 24th, 2025 at 11:41 am
Ted #10:
But on the other hand, I assume that while you can allow most of your qubits to fully decohere before you start your computation within this model, once you start the computation you need to prevent any additional external entanglement with the environment just as usual. And my understanding is that state preparation is rarely the practical implementation bottleneck for today’s quantum computers. So my guess is that implementing this model experimentally is probably 99.99% as hard as implementing traditional quantum computers, for a less powerful payoff – so not useful in practice.
Yep, that’s 100% correct!
The big surprise is that the one-clean-qubit model, despite having limited practical relevance for exactly the reason you say, ends up having more complexity-theoretic relevance than you’d have any right to expect.
Both with KLM and with the one-clean-qubit model, I see Ray as a physicist who stumbled against his will into doing complexity theory … something I loved to tease him about, as with my talk at his birthday conference!
Comment #14 June 24th, 2025 at 12:20 pm
Huh — I remember the big hubbub over “catalytic computing” a few years ago (and which just recently led to this new time/space result of Williams!), but I don’t remember ever hearing about “one clean qubit”, even though they seem quite similar in spirit… indeed, with classical computation, you could define the same thing, except now the “maximally mixed state” is a uniform probability distribution instead of a quantum state, and then it really starts to look like catalytic computing! Is “one clean qubit” basically the quantum version of catalytic computing? Did the quantum version come first here??
Comment #15 June 24th, 2025 at 12:59 pm
Sniffnoy #14: Turns out you’re absolutely right that there’s a connection between catalytic computing and one-clean-qubit! See this arXiv preprint from 5 days ago (!!), which fleshes the connection out (and also clarifies the differences). But yes, the one-clean-qubit model came first.
Comment #16 June 24th, 2025 at 1:35 pm
Sorry for you loss, and obviously also a great loss for Canada, my chosen home nation. May his memory be a blessing.
Comment #17 June 25th, 2025 at 2:15 am
I too was sad to hear the news, I last met Raymond briefly in May 2024, when I popped in an IQC event during a conference at PI. At the time I was just glad to see Raymond, as I took it as a sign that his disease was under control…
Besides his contributions to experimental NMR, linear-optical quantum computation, and fault-tolerance, his DQC1 model is, I think, a precursor to Hadamard tests for measuring Paulis, error syndromes, Bargmann invariants, error mitigation, and so on. DQC1 was designed to work with mixed states, whereas these other applications extract useful information on more general states.
Raymond was also very kind and a good mentor to many people I knew during my postdoc years at PI (2002-2005). I remember fondly of his kind invitation to me and a few others to spend our first Christmas in Canada at his home with his family, in a very heart-warming Canadian welcome. He’ll be greatly missed.
Comment #18 June 25th, 2025 at 9:56 am
Sad news. I met Ray in person only once, at a lovely 2013 conference—QSTART—that we organized in Jerusalem to inaugurate our quantum science center. I had the chance to chat with him about several topics, including his personal account of the development of the vastly important threshold theorem. At that conference, Ray gave a great opening talk on experimental quantum error correction. I remember being impressed throughout that week by Ray’s personality and sense of humor.
I also had the pleasure of meeting Ray virtually during a 2022 Zoom lecture I gave at the Perimeter Institute. I was happy he chose to attend my talk instead of watching the World Cup semifinal between France and Morocco! He asked excellent questions that sparked a delightful discussion.
Let me also mention that Ray Laflamme recently co-authored a book with Shayan Majidy and Christopher Wilson: Building Quantum Computers: A Practical Introduction.
Comment #19 June 26th, 2025 at 4:44 am
Scott #12
I wrote what I did because I sincerely like to read what you have to say about QC, and even about AI, and also think that what you write about political matters is helping no one, least of all yourself.
I wouldn’t normally give advice, but since you are asking for it, I would suggest
1) Make sure that your family has a comfortable and well-guarded community in which to live. As the US continues to descend into dysfunction (North Brazil is the optimistic scenario), this is important regardless of whether you think the main threat is from the right or the left.
2) Stop thinking and talking so much about politics, because personal political preference has little to no bearing on what will happen, but more importantly because different political preferences are often fundamentally at odds, so by taking public political stances, we mark as ourselves as enemies to people with whom we could otherwise cooperate. I’d have no problem working with you as a colleague or having you as a neighbor, but from what I’ve seen on this blog, it seems to me pointless to try to have even a purely intellectual political conversation as our basic intuitions and frame of reference are too divergent.
Comment #20 June 26th, 2025 at 7:25 am
CB #19: That’s a shame—you seem nice and sane, and I pride myself on being able to have a friendly conversation on just about anything with any other nice and sane person. From this comment section, it might look like I’m constantly in bitter arguments, but from my perspective, that’s only because the prevalence in this comment section of people who are either not nice, not sane, or both is wildly greater than in my real life. Maybe I just live in a bubble.
I did hope the obvious fact that I’m willing to call out mendacity and insanity on both the left and the right would help me find common ground with anyone, but the pessimistic view would be that it just alienates me from everyone.
Comment #21 June 26th, 2025 at 7:27 am
I vehemently disagree with CB that you should stop talking politics. It’s not that Im a universal fan of them – I feel like you waffle between being aligned on the big picture and core values with me, but then in other moments launch in with “both sides” rhetoric that makes me feel rather frustrated. Or maybe you and your values don’t waffle but your writing does, as the emphasis shifts around based on what’s happening and who needs more convincing, is perhaps the more accurate take.
No matter. “Politics” isn’t away and out there. And you can’t opt out from it’s effects – so I’d say far from encouraging opting out from the dialog, to do so would be cowardly! We need this! It’s not not like choosing not to care about the NBA finals.
I’ll make it computing relevant by quoting my favorite Hacker Koan
In the days when Sussman was a novice, Minsky once came to him as he sat hacking at the PDP-6.
“What are you doing?”, asked Minsky. “I am training a randomly wired neural net to play Tic-tac-toe”, Sussman replied. “Why is the net wired randomly?”, asked Minsky. “I do not want it to have any preconceptions of how to play”, Sussman said.
Minsky then shut his eyes. “Why do you close your eyes?” Sussman asked his teacher. “So that the room will be empty.” At that moment, Sussman was enlightened.
Comment #22 June 26th, 2025 at 3:05 pm
A truly beautiful memorial.
Comment #23 June 26th, 2025 at 3:48 pm
Ted #10 and Scott #13: Once a DQC1 computation starts, I don’t think you need to prevent the maximally mixed qubits from undergoing unitary or unital interactions with the environment.
Comment #24 June 26th, 2025 at 5:07 pm
I am with Doug #21. Scott created and runs this blog and he can decide what he wants to talk about. CB can start his/her own blog and make up the rules.
Comment #25 June 26th, 2025 at 6:09 pm
SB #23: The issue is that, because of interactions with the clean qubit, once the computation starts those qubits might no longer be maximally mixed (or they might be individually, but also be correlated with other qubits), in which case you do need to protect them.
Comment #26 June 27th, 2025 at 4:35 pm
Scott #25: Thanks, Scott. I can see why you’re right. Sorry for your loss.
Comment #27 June 28th, 2025 at 8:01 am
I joked with him about “our famous complexity theorist.” He said, “I’m not sure if Scott is trying to bring me up or bring complexity theory down,” with his typical smile.
Comment #28 June 28th, 2025 at 12:54 pm
Scott #15: Further evidence that when people come up with something quantum, they should make sure they’ve thought about the classical analgoue too!
Comment #29 June 28th, 2025 at 1:17 pm
Sniffnoy #28: Catalytic is not a direct classical analogue of the one-clean-qubit model, although it’s closely related.
Comment #30 June 28th, 2025 at 2:16 pm
Sure, but you could do a direct classical analogue! (And then that direct analogue might lead you there.) I was going to ask “has anyone considered that”, and then I realized, wait I should actually take a better look at the paper you linked to first see what it has to say…
Comment #31 June 29th, 2025 at 1:16 am
Thank you Scott for this informative tribute. I did not know him, but became familiar with his name from publications. Therefore, when I saw his passing on Wikipedia, we went to the page about him to see why he passed at such a relatively young age. Your tribute makes me proud of Canada for punching so high in this field.
My interest in QC is limited to the notion of classical simulations of quantum computing and what it says about complexity. (It has lead me to doubt strongly whether there really is any quantum advantage.) This brings me to the KLM theorem showing how simple it is to implement universal quantum computing. Is it my imagination or can all these basic processes be efficiently simulated on a classical computer?
Comment #32 June 29th, 2025 at 3:08 am
flippiefanus #31: No, once you have universal quantum computation, the whole point is that it can’t be efficiently simulated classically in general, not unless BPP=BQP and factoring for example is classically easy.
Comment #33 June 29th, 2025 at 12:28 pm
Oh, wait, I’m being dumb — the direct classical analogue of “1 clean qubit” is actually quite pointless. OK, it definitely does take additional work to invent catalytic computing!
Comment #34 June 29th, 2025 at 11:46 pm
Scott #32: Thanks for the clarification. I understand that it is the general argument. My doubt comes about because I think perhaps it is not necessary for BPP=BQP. The classical simulation only needs to *approximate* the quantum computing. It is similar to the fact that digital computers can approximate computations with real numbers even though they can only represent integers. I guess it would be possible if we can assumes that BPP is dense in BQP, similar to how rational numbers (ratios of integers) are dense in the space of real numbers.
Comment #35 June 30th, 2025 at 8:49 am
Hi Scott. Why does DQC1 not get mentioned very much in discussions of quantum speedups? Where would it go on your field guide to big quantum speedups?
Comment #36 June 30th, 2025 at 9:16 am
SB #35: Because DQC1 isn’t itself a “speedup”; it’s a sub-universal computational model in which speedups can exist. The speedups in question would be for (eg) estimating the traces of unitary matrices or the trace closure of the Jones polynomial of a braid. These do get mentioned from time to time, but finding real-world applications of them is not surprisingly a much harder task.
Comment #37 July 3rd, 2025 at 6:18 am
Scott #36: Thanks, Scott. When a useful application is appended onto a model of quantum computation in which speedups can exist is that exciting? Or does a lot of complexity-theoretic fine print need to be worked out first? For example, there is a paper about molecular docking with Gaussian boson sampling. Somewhat similarly, I saw that in 2019, Ghobadi et al. investigated whether the DQC1 algorithm for normalised trace estimation could be used for quantum machine learning.
Comment #38 July 29th, 2025 at 6:39 pm
Gil Kalai* pointed to both our blog posts about Ray,** making me a little shocked at how similar they are in some ways. Ray had a very consistent style—and French-Canadian accent tinged with a smile.
*https://gilkalai.wordpress.com/2025/07/30/some-questions-from-recent-quantum-events/
**Mine’s at https://quantumfrontiers.com/2025/07/27/little-ray-of-sunshine/.