Congrats to Bennett and Brassard on the Turing Award!
I’m on a spring break vacation-plus-lecture-tour with Dana and the kids in Mexico City this week, and wasn’t planning to blog, but I see that I need to make an exception. Charles Bennett and Gilles Brassard have won the Turing Award, for their seminal contributions to quantum computing and information including the BB84 quantum key distribution scheme. This is the first-ever Turing Award specifically for quantum stuff (though previous Turing Award winners, including Andy Yao, Leslie Valiant, and Avi Wigderson, have had quantum among their interests).
As a practical proposal, BB84 is already technologically feasible but has struggled to find an economic niche, in a world where conventional public-key encryption already solves much the same problem using only the standard Internet—and where, even after scalable quantum computers become able to break many of our current encryption schemes, post-quantum encryption (again running on the standard Internet) stands ready to replace those schemes. Nevertheless, as an idea, BB84 has already been transformative, playing a central role in the birth of quantum information science itself. Beyond BB84, Bennett and Brassard have made dozens of other major contributions to quantum information science, with a personal favorite of mine being the 1994 BBBV (Bennett Bernstein Brassard Vazirani) paper, which first established the limitations of quantum computers at solving unstructured search problems (and indeed, proved the optimality of Grover’s algorithm even before Grover’s algorithm had been discovered to exist).
While I take my kids to see Aztec artifacts, you can learn much more from Ben Brubaker’s Quanta article, to which I contributed without even knowing that it would be about Bennett and Brassard winning the Turing Award (info that was strictly embargoed before today). It’s an honor to have known Charlie and Gilles as well as I have for decades, and to have been able to celebrate one of their previous honors, the Wolf Prize, with them in Jerusalem. Huge congrats to two of the founders of our field!
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Comment #1 March 18th, 2026 at 12:39 pm
I actually admire Bennett even more for other work he’s done – about the Maxwell demon/Szilard/Landauer stuff, and for the Bennett Acceptance Ratio (BAR).
Obviously a chart-topper, not a one-hit wonder!
Comment #2 March 18th, 2026 at 1:31 pm
Congratulations to this year’s Turing Award laureates!
According to La Presse, Gilles Brassard will participate via videoconference, explaining: “As long as the little dictator is in power, I’m not going to the United States under any circumstances—not even for that.”
Comment #3 March 18th, 2026 at 3:21 pm
As a relative nobody in the field, I am thrilled to have been able to meet both of them. Bennett was my first professional hero. Both were quite delightful and easily approachable for a lowly student (I met Bennett in college and Brassard in grad school). I remember Gilles saying that the first experimental realization of BB84 made a loud thunk whenever the polarization changed, so it was provably unconditionally secure against any deaf eavesdropper! Congrats to both of them!
Comment #4 March 19th, 2026 at 5:00 pm
Does not BB84 have a problem with authenication?
Comment #5 March 19th, 2026 at 6:40 pm
Have a nice holiday, Scott. When you get back, I recommend that you get into optical computing. I say that because because after nearly 60 years, quantum computing just isn’t going anywhere. Don’t waste your life. Hup hup1
Comment #6 March 19th, 2026 at 7:42 pm
Congrats to Bennett and Brassard! I’ve never met Bennett but I knew Brassard slightly a long time ago (I was a newbie undergrad at the time). I was familiar with big-O notation before I met him, but he had a handout on the topic for a class he was teaching, and it was the first time I saw that it made any mathematical sense, and that CS was an actual mathematical topic rather than an area where one could use mathematical tools. Basically he defined O(f) as the set of functions g such that blah blah, i.e. it was precise rather than handwavy. He similarly had big-Omega and big-Theta. It was an eye opening moment. Lots of people were using O to mean Theta, fwiw.
Meanwhile, something off topic from the Turing award but quantum related. I’ve heard of the Butterfly Effect described as a butterfly flapping its wings in Brazil affecting a thunderstorm in Texas or whatever. I.e. the effect is propagated through collisions of air molecules in chaotic motion, so both endpoints in the story are on Earth. I’m wondering if it’s actually cosmic in scale because of quantum entanglement. Can it be that a butterfly-oid organism flapping its wings on the planet Zaldor-Q23 in the Andromeda Galaxy collapses some quantum states that are entangled with those of air molecules in Texas, affecting the Texas weather in sort of the same way?
Comment #7 March 19th, 2026 at 10:29 pm
John Duffield #5: Not interested in a debate. Only want to know: if fault-tolerant Shor’s algorithm is used to factor large numbers in the relatively near future, will you come back here to admit you were wrong, or will you have some way to explain away even that?
Comment #8 March 20th, 2026 at 9:23 am
asdf #6 “Lots of people were using O to mean Theta, fwiw.”
Big Theta implies big O, and usually big O is what anyone really cares about, which is why it is common to use O even if something is actually Theta.
Also, big and little O (Landau Order symbols) go back at least 100 years, and have always been used extensively in math. Knuth then extended the idea to Theta and Omega around 50 years ago, and also renamed O to Omicron for consistancy.
BTW, never under any circumstances spell O as Oh — that is just wrong.
Comment #9 March 20th, 2026 at 11:21 am
Congratulations to them.
However, I find it really weird that CS’s highest honor is being awarded to dudes that did work of an absolute theoretical nature so much that we do not have any semblance yet that the work will yield any practical implementations/results. I mean, isn’t that why Stephen Hawking never won the Physics Nobel? Same reason Ed Witten is yet to win a Nobel. Same reason Einstein was not awarded for relativity but instead got it for the photoelectric effect. Same reason it took a while for Sir Roger Penrose to get a Nobel.
I understand CS is a science, but science is meant to have instrumental value. It is not mathematics that can be intrinsically illuminating and as such mostly a formal science, with intrinsic value. Real science is meant to be applied. It is meant to make the world practically different in some way.
Even when we attempt to consider their work to be in the pantheon (to use this term loosely) of TCS and perhaps a formal science, it still does not possess the flavor of other works of TCS nature that have been awarded the prize. The other works of TCS nature that have been awarded like those dealing with cryptography, computational complexity, etc, have had real insights to offer.
Quantum computing and all of its sisters is really just beautiful math for now till the work amounts to something of value in the real world. Till then, we should be cautious how we award prizes that signal transformative work to such fields.
Just my honest opinion.
Comment #10 March 20th, 2026 at 11:33 am
Ayokunle Afuye #9: Even the Nobel Prize in Physics regularly gets awarded for work of no conceivable practical value in the foreseeable future — as long as the work can be connected to an experiment. Even Penrose was eventually awarded the prize for his work on black holes, which strongly suggests that Hawking would have won it as well had he lived longer.
But the Turing Award doesn’t even have that requirement. It’s been awarded, for example, to Hartmanis and Stearns and to Avi Wigderson for breakthroughs that were entirely theoretical in nature (can you tell a story that relates them to something practical? sure you can, but you can do the same for BB84). At the other end of the spectrum, the Turing Award was also given to (eg) Doug Engelbart and Fred Brooks for work that was entirely practical in nature, with no mathematical theory behind it at all. This seems fine to me.
Comment #11 March 20th, 2026 at 2:32 pm
Thank you for your note, Scott.
I was going to mention something about Wigderson’s win but that would require a whole paragraph on its own. However, let me attempt my full remarks while addressing the points you have raised:
1. Yes, the Nobel is often awarded for theoretical work so long it is linked to an experiment, just as you have mentioned. But that awarding only happens when the experimental confirmation has occurred. Consider Peter Higgs- it was until the Large Hadron Collider was used to detect the properties of the predicted Higgs’ Boson. The same goes for Penrose, who wasn’t awarded the prize till the existence of black holes were confirmed practically through the work of Genzel and Ghez, with one-half going to Penrose and one-half going to the duo.
2. On Wigderson, I think it is mostly for his decades of intellectual leadership in theoretical computer science, rather than his work on the role of randomness in computation and mathematics. He has done so much for TCS and has never shied away from the fact that his work is purely theoretical and mostly exist as underpinning some of the revolutionary technology and science that we have. He considers TCS a serious mathematical discipline. Still, I think his should have been a shared prize with Papadimitriou who has done just as much for the field. They have mostly been the two guiding lights of TCS.
3. On Doug Engelbart and Fred Brooks, I would think that CS of a straightforwardly practical nature that has advanced the field axiomatically deserves the prize.
But my view remains that the highest honour in CS should not go to peeps with work of “no conceivable practical value in the foreseeable future,” to use your own words.
Theoretical work is often needed as that is mostly how the field is advanced and most of the TCS work that has been awarded did something of value for CS.
Comment #12 March 20th, 2026 at 2:41 pm
Ayokunle Afuye #11: I’m sure that that argument was made within the prize committee, and apparently it didn’t carry the day. As a general rule, I don’t respond to announcements of major awards by publicly arguing that the recipients shouldn’t have gotten them, except perhaps in egregious cases. And everyone agrees that Charlie and Gilles are intellectual giants who helped found the entire field of quantum information science. I, too, might have waited for clearer practical impact before awarding a Turing Award for QIS, but if the committee wanted to do it now, who am I to argue? 🙂
Comment #13 March 20th, 2026 at 2:51 pm
Fairs! Thanks, Scott!
Comment #14 March 20th, 2026 at 4:42 pm
Congratulations to Bennett and Brassard! I remember being a nerdy teenager and reading a 1992-ish Scientific American article about the original BB84 machine built by Bennett, Brassard, Smolin and friends. I later wondered whether the machine was still extant – and I was pleased to find out that Bennett had kept it in his office at Yorktown Heights, producing it around ~2016 or so to show to an interviewer for a documentary on Bennett’s life and outlook and experience.
Could – or should – the machine, as noisy as it was, eventually be donated to a good computer history museum, especially now after Bennett and Brassard’s Turing win? Can it colorably lay claim to be one of the first “quantum” computers, even though it operates only on unentangled qubits between Alice and Bob (and Eve)?
Comment #15 March 20th, 2026 at 6:00 pm
Mark Spinelli #14: No, I wouldn’t call the first QKD device a “quantum computer” (and I doubt Bennett and Brassard would either), but all the same, if it still exists, it certainly would merit a spot at the Computer History Museum in Mountain View (one of my favorite museums) or a similar place!
Comment #16 March 22nd, 2026 at 3:08 pm
> However, I find it really weird that CS’s highest honor is being awarded to dudes that did work of an absolute theoretical nature so much that we do not have any semblance yet that the work will yield any practical implementations/results.
If one reads Gödel’s therapist’s notes, they mostly record complaints by Gödel about his lack of personal progress in science (… until he succumbed to anorexia).
If anything, the highest honor should recognize researchers obsessed with rigorous what-ifs and counterfactuals. If the work is technically sound and expands the community’s understanding of computation, that matters A LOT, even before the community knows how to build the machine that would realize such computation.
Comment #17 March 22nd, 2026 at 6:00 pm
@cananon #2
If true, that’s interesting political commentary by Brassard. Boycotting the U.S. over ‘authoritarianism’ while living under a government that froze protesters’ bank accounts and is flirting with pre-crime speech laws is… an interesting line to draw.
Comment #18 March 22nd, 2026 at 6:42 pm
I don’t see any issue with theorists getting Turing awards. Theory is a perfectly good part of CS. Turing himself was mostly a theorist, after all.
https://en.wikipedia.org/wiki/Turing_Award#Recipients shows multiple theorists who have gotten it, though mostly for work that has affected practice. But an obvious hypothetical example: a real P!=NP proof would surely deserve the award (plus the Millenium prize and maybe the Fields medal) even though it wouldn’t have any likely practical effect on anything. There’s lots of other possibilities too.
Comment #19 March 23rd, 2026 at 4:41 pm
Anyone have thoughts on “Quantum computers could have a fundamental limit after all”,
https://phys.org/news/2026-03-quantum-fundamental-limit.html ?
Comment #20 March 23rd, 2026 at 5:16 pm
Raoul Ohio #19: Yes. My thought is that the “fundamental limit to quantum computers” would apply if, and only if, Tim Palmer’s discrete superdeterministic theory were to be true and replace quantum mechanics. If so, that would be by far the biggest revolution in physics for a century, and quantum computers not working would be the least of it. I’m willing to bet a large amount of money that this will not happen.
Comment #21 March 23rd, 2026 at 5:21 pm
Max #17,
No doubts someone, somewhere can cook up a metric where Canada looks more authoritarian than Trump’s U.S. Good luck believing that’s what sanity looks like. 🙂
Comment #22 March 23rd, 2026 at 10:46 pm
Scott #20:
ha -ha, that puts an alternative spin on things.
Comment #23 March 24th, 2026 at 2:24 pm
Raoul Ohio #22: No, it’s actually the completely conventional spin on things … the one that foresees the known laws of physics continuing to hold!
Comment #24 March 24th, 2026 at 3:24 pm
Congratulations to the Turing recipients !!
Anybody has thoughts on TN-based Schnorr’s sieving to factor integers: https://journals.aps.org/pra/pdf/10.1103/d9dl-ctt4
Comment #25 March 24th, 2026 at 5:03 pm
Joydip #24: It looks like more garbage to me (there’s a huge amount in this subject). If they’re right, then factoring is in classical P, but I don’t see how they could be right if they throw away the special structure of factoring and treat it as just another combinatorial problem. How do we know that what forced them to stop at an unimpressive 100 bits wasn’t, y’know, exponential scaling, just like with every other classical approach to factoring?
Comment #26 March 26th, 2026 at 9:00 am
@cananon #21 This doesn’t really engage with the argument—it’s just dismissive without offering a rebuttal.
On specifics: Canada does have weaker free-speech protections than the U.S. (e.g., broader limits under its constitutional framework and hate-speech laws). During the trucker convoy, the government even used emergency powers to pressure financial institutions to freeze accounts—and Justice Richard Mosley of the Federal Court of Canada later ruled that invocation of the Emergencies Act was unlawful.
More broadly, there have been repeated legislative efforts to expand regulation of online speech, such as Bill C-10 / Bill C-11 and Bill C-36, including proposals that would allow restrictions/penalties based on anticipated future harm (rather than completed acts).
Maybe you’re knowledgeable on all of this and think it’s justified, but that’s not coming across.
Comment #27 March 26th, 2026 at 10:26 pm
Max #26,
Fine—let’s pretend this deserves a careful response rather than an eye roll.
The steelman version of your argument goes roughly like this: Canada is sliding into authoritarianism because of bank‑account freezes, speech restrictions, and pre‑emptive regulation, while the United States remains a fundamentally freer society.
The small problem is that this argument never actually compares Canada to the United States. It puts Canadian edge cases under a microscope, then quietly waves away the U.S. equivalents—despite operating at a vastly larger scale and with considerably more nastiness. If you want to check this for yourself, here are a few starting points.
If account freezes and financial coercion keep you up at night, you might enjoy reading about Operation Choke Point —a textbook case of financial coercion achieved not through legislation or courts, but through informal regulatory pressure designed to make lawful actors effectively unbankable. A more recent example is the U.S. use of extraterritorial sanctions against allied officials like Thierry Breton, for the crime of enforcing democratically adopted regulations.
If privacy and free speech are your concern, look into FISA 702 which allows U.S. intelligence agencies to collect massive volumes of communications without individual warrants by compelling tech companies to hand over data; and the CLOUD Act, which extends that reach globally by forcing U.S. firms to provide access to data stored abroad, regardless of local law.
If, after reading about all this, you still don’t get that the U.S. threatens freedom by orders of magnitude more than Canada, then let’s look at authoritarian actions that don’t even have a smaller Canadian equivalent. Here’s a non‑exhaustive list from recent U.S. history:
### Concrete authoritarian actions under the Trump administration (2017–2021)
– **Attempted overturning of an election**
Trump and senior officials pressured state election administrators, the DOJ, and the Vice President to overturn certified results—promoting knowingly false fraud claims and culminating in January 6.
– **Use of federal force against civilians and protesters**
Federal agents were deployed to cities like Portland without clear identification, engaging in warrantless detentions and crowd suppression. Peaceful protesters were forcibly cleared from Lafayette Square for a presidential photo op.
– **Politicization of the Department of Justice**
Trump intervened in cases involving allies (Flynn, Stone) while demanding investigations into political opponents, openly treating the DOJ as a personal enforcement arm.
– **Abuse of emergency and executive powers**
When Congress refused border‑wall funding, Trump declared a national emergency to bypass the legislature and redirect military funds—explicitly because Congress said no.
– **Systematic attacks on the free press**
Journalists were routinely labeled “enemies of the people,” credentials were threatened or revoked, and defamation laws were floated as tools to punish critical coverage.
– **Loyalty over law**
Officials were fired or sidelined for insufficient personal loyalty (Comey, Vindman, Esper), while loyalists were rewarded regardless of competence or legality.
– **Family members embedded in state power**
Jared Kushner and Ivanka Trump exercised enormous unelected authority over policy and crisis response, bypassing normal accountability mechanisms.
– **Encouragement of political violence and intimidation**
Violence by supporters was minimized, excused, or rhetorically encouraged (“very fine people,” “stand back and stand by”).
– **Obstruction of oversight**
Blanket refusals to comply with subpoenas and testify before Congress were used to neutralize institutional checks.
– **Normalization of an authoritarian executive theory**
Repeated claims that Article II allowed the president to “do whatever I want” reflected a deeply personalist conception of power.
I might also mention market manipulation. When nearly $600 million in oil trades line up perfectly minutes before a presidential announcement and cash out immediately afterward, the coincidence defense stops being implausible and starts being insulting. To be fair, this is less textbook authoritarianism than kleptocracy, like grabbing pussy tells more about your chance of being a child abuser than an authoritarian leader.
Comment #28 March 28th, 2026 at 11:29 am
@cananon #27
Your response still feels like it’s talking past the original point. Brassard’s claim that Trump is a “little dictator” [1] reflects a selective standard, given comparable issues in Canada.
If Brassard’s (and your) concern is surveillance or media pressure, those predate Trump—e.g., FISA expansion under Obama—so invoking them here just highlights the double standard. And several of your other examples cut both ways. DOJ politicization? Consider the prosecution of Eithan Haim. Media pressure? Obama openly attacked Fox as partisan, and the Hunter Biden laptop story and COVID-related dissent were both suppressed with government pressure in the background. Financial pressure? The Obama-era Operation Choke Point (as you mention) involved regulators leaning on banks to cut off lawful businesses without court orders. If these count as “authoritarian,” then the issue is broader and bipartisan.
But all of this still avoids the Canada point. The argument wasn’t that Canada has the same global impact as the U.S., but that it’s inconsistent to condemn “authoritarianism” abroad while downplaying similar issues at home, like weaker speech protections, compelled-speech concerns, and hiring policies that discriminate based on race or identity (e.g., SFU, Dalhousie, and UWaterloo [2]). And the Emergencies Act wasn’t just about freezing bank accounts—it included restrictions on assembly, compelled services, and expanded policing powers, and was later ruled unlawful. There are also recent examples touching on personal property and firearm rights, such as court rulings affecting land claims (e.g., Cowichan) and a national firearm prohibition and forced buyback scheme. These aren’t edge cases; they’re sad and predictable results of the legal/constitutional framework in Canada.
So there are two coherent arguments you could make: a comparative one (Canada is better), or a systemic one (civil liberties issues in the U.S. span administrations). I’m open to either. But right now you’re mixing them—criticizing the U.S. (1) without applying the same standard to Canada, and (2) by framing broader, bipartisan issues as uniquely Trump-era.
If you want to argue Canada is better, cool, clearly I disagree, but please make that case directly. If you want to argue the U.S. has broader civil liberties issues, then I likely agree with you, so long as it’s acknowledged as a bipartisan problem.
——–
[1] “As long as the little dictator is in power, I’m not going to the United States…”
[2] https://philjobs.org/job/show/30170
https://www.dal.ca/dept/hr/employment_equity/fair-hiring-practices.html
https://uwaterloo.ca/research/sites/default/files/uploads/documents/am-crctier1ad-final-accessible.pdf