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John Watrous

@johnwatrous.bsky.social
901 followers 180 following 41 posts

Quantum computing educator and researcher. I like math, computer games, and dub techno.

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John Watrous @johnwatrous.bsky.social · 02/08/2025
Bluehost seems to be holding my domain name hostage, I gather in an effort to sell me more products and services. Avoid them at all costs. But see if I care. Hereafter you can find my web page at jhwatrous.github.io in case you're looking for it.
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John Watrous @johnwatrous.bsky.social · 29/07/2025
That one episode where they diagonalize is great. So many other shows try to replicate it.
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John Watrous @johnwatrous.bsky.social · 23/07/2025
I ditched my old website and created a new one on GitHub Pages: johnwatrous.com It's a great option for a static web page, particularly if you like to do your own CSS styling rather than flipping through pre-built templates that are never quite right.
johnwatrous.com
About - John Watrous
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John Watrous @johnwatrous.bsky.social · 17/07/2025
It does not. I resigned my faculty position at the end of 2021 and haven't taught an actual course with registered students since then. But isn't any course unfinished by definition so long as one is teaching it?
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John Watrous @johnwatrous.bsky.social · 16/07/2025
After 3 1/2 years of work my course on quantum computing is finally finished — the "Director's Cut" of Understanding Quantum Information and Computation is now available. arxiv.org/abs/2507.11536
arxiv.org
Understanding Quantum Information and Computation
This is a course on the theory of quantum computing. It consists of 16 lessons, each with a video and written component, covering the basics of quantum information, quantum algorithms (including query...
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John Watrous @johnwatrous.bsky.social · 02/04/2025
With Chris Knight, Val Kilmer demonstrated that a character can simultaneously be incredibly smart, cool, fun, and genuinely kind. Real Genius was a special movie.
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Reposted by John Watrous
Felix Leditzky 🏳️‍🌈🏳️‍⚧️ @felixled.bsky.social · 27/03/2025
I've been revamping and updating my collection of selected references to topics in quantum information on my homepage. Comments, feedback and suggestions welcome! felixleditzky.info/selected_ref...
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John Watrous @johnwatrous.bsky.social · 10/03/2025
Excellent lecture notes by Richard Kueng on theory of computing and quantum computing.
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John Watrous @johnwatrous.bsky.social · 09/01/2025
Totally awesome. And be sure to check out Nathaniel's 140 other videos on calculus, linear algebra, and Conway's game of life. Thank you Nathaniel for making these videos available to the community. And for QETLAB! www.youtube.com/@NathanielMath njohnston.ca/my-websites/
youtube.com
Nathaniel Johnston
I am an Associate Professor of Mathematics at Mount Allison University in New Brunswick, Canada. Most of my videos are lectures that are meant to accompany undergraduate courses that I teach.
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John Watrous @johnwatrous.bsky.social · 07/01/2025
This reminds me of a QIP talk years ago where someone introduced a technique on some thing or another by some new name. Reinhard Werner was sitting nearby and he muttered, not quite under his breath, "It's called matrix multiplication."
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John Watrous @johnwatrous.bsky.social · 02/01/2025
Where to begin? Writing letters, email, reports, trip planning, travel claims, presentations, cleaning, organizing, doing laundry, shovelling snow, trying to get this classical computer in front of me to function properly. Probably not all that much different from any other theorist.
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John Watrous @johnwatrous.bsky.social · 02/01/2025
For getting unexciting stuff done, nothing works better for me than setting a timer: 10 minutes, 90 minutes, whatever makes sense. When time's up, I move on to something else and repeat later. It's remarkable what you can accomplish when you just put in the minutes.
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John Watrous @johnwatrous.bsky.social · 09/12/2024
Of course, in an ideal world, each paper would receive multiple carefully written reviews that explain the decision in detail. But recognize that this means even more work for others. A preferable solution in my view: people should stop writing so many damn papers!
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John Watrous @johnwatrous.bsky.social · 09/12/2024
I think this is it right here. I have felt the frustration of poor reviews — but I've also chaired the QIP PC and served many times, and it's a thankless monster of a job. Most papers will not make the cut for the simple reason that others are seen as stronger.
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John Watrous @johnwatrous.bsky.social · 08/12/2024
Making pizza turned out to be incredibly valuable: I still make pizza at home almost every week. Not so much for being a cashier, except maybe for developing empathy for cashiers. Customers can be pretty difficult, as I'm sure anyone who is or was a cashier knows very well.
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John Watrous @johnwatrous.bsky.social · 08/12/2024
Here's my work history: Pizza maker Grocery store cashier Blockbuster Video cashier Math tutor Teaching/research assistant Postdoc Professor IBM Quantum educator I guess you took the faster route.
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John Watrous @johnwatrous.bsky.social · 06/12/2024
I believe this is because everyone is left-handed in Australia.
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John Watrous @johnwatrous.bsky.social · 05/12/2024
Hang in there, they grow up. Before you know it you'll be back to normal gaming hours.
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Reposted by John Watrous
Lance Fortnow @lance.fortnow.com · 04/12/2024
Now in one place, my sixty favorite theorems covering the six decades of computational complexity. blog.computationalco...
blog.computationalcomplexity.org
Favorite Theorems: The Complete List
Now in one place all of my sixty favorite theorems from the six decades of computational complexity (1965-2024). 2015-2024 Graph Isomorphism...
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John Watrous @johnwatrous.bsky.social · 03/12/2024
I edit source files in Emacs, run LaTeX from a terminal window, and let Skim auto-reload to see the results, everything local. Feeling like an old-school Gen Xer who mostly works alone. But then again, everything is working fine for me today.
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Reposted by John Watrous
Nathaniel Johnston @njohnston.ca · 03/12/2024
Overleaf's down, so I'm cancelling research for the day. Everyone go home and play Slay the Spire.
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John Watrous @johnwatrous.bsky.social · 03/12/2024
I have not played it. It appears to be about 30 years old, which is pretty darn old for a video game. That's like, pre-Black Isle Studios old. Has it stood up this long? Not impossible — I still play Super Metroid on SNES when I visit my childhood home.
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John Watrous @johnwatrous.bsky.social · 03/12/2024
I did play Inscription. It was intriguing and fun, but I didn't love it — I guess I found the actual card game itself to be a bit dull and tedious at times.
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John Watrous @johnwatrous.bsky.social · 02/12/2024
Downloading...
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John Watrous @johnwatrous.bsky.social · 01/12/2024
In that case, yeah — this one is probably not for you. (Not sure what to feel right now, having put several hundred hours into Civ 6.)
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John Watrous @johnwatrous.bsky.social · 01/12/2024
Regarding characters, I love The Defect, but I'd be lying if I didn't admit that The Ironclad is my favorite to play.
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John Watrous @johnwatrous.bsky.social · 01/12/2024
But you could die at any time, and when you're dead your dead. So you start a new run. In summary, I don't need motivation to play, I need motivation not to play!
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John Watrous @johnwatrous.bsky.social · 01/12/2024
Synergies can be unexpected and incredibly powerful — almost like you've broken the game sometimes. That can be so satisfying! I've actually woken up my son to show him how some killer deck I've built one-shots a boss.
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John Watrous @johnwatrous.bsky.social · 01/12/2024
Slay the Spire is all about synergies between your cards and relics, but the choices you're presented with on each run are random. So games are always different and you can't adopt a single strategy, you have to build around what you're offered.
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John Watrous @johnwatrous.bsky.social · 30/11/2024
It is my honest opinion that Slay the Spire is one of the greatest games of all time. Greater than infinite replay value — it gets better the more you play. And please don't say Balatro, that game is pretty good but not as good. Just my opinion.
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John Watrous @johnwatrous.bsky.social · 29/11/2024
Stack Exchange doesn't cost anything. What does free mean in this context? Not-for-profit? Open-source?
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John Watrous @johnwatrous.bsky.social · 28/11/2024
The fact that I actually get this makes me feel like I probably watched too much TV when I was young.
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John Watrous @johnwatrous.bsky.social · 28/11/2024
Tank Man. Because Gisèle Pelicot was already suggested.
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John Watrous @johnwatrous.bsky.social · 28/11/2024
I find it remarkable that an upvote on a question or answer costs absolutely nothing to whoever gives it — and yet the person on the receiving end derives something positive from it. I suppose it's about people feeling that their contributions are appreciated. Also great for sorting.
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John Watrous @johnwatrous.bsky.social · 28/11/2024
Quantum Computing Stack Exchange has the potential to be a resource of great value, but the only source for its value is its users (not unlike Bluesky). So I hope some will consider participating, whether by asking or answering questions or just giving some upvotes.
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John Watrous @johnwatrous.bsky.social · 28/11/2024
Check out this question and the answers it received for an indication of how far people will go, basically just for fun. tex.stackexchange.com/questions/29...
tex.stackexchange.com
How do I make my document look like it was written by a Cthulhu-worshipping madman?
I want to type up some spells from the RPG Call of Cthulhu and give them to my players. I could just type them up in Word or LaTeX, but that seems too...neat. I'd like to make these things look lik...
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John Watrous @johnwatrous.bsky.social · 28/11/2024
As a point of comparison, TeX - LaTeX Stack Exchange is an incredibly valuable resource to me personally. I depend on LaTeX Beamer and TikZ for my work and TeX - LaTeX Stack Exchange is typically where I learn how to do new things with these tools. tex.stackexchange.com
tex.stackexchange.com
TeX - LaTeX Stack Exchange
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
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John Watrous @johnwatrous.bsky.social · 28/11/2024
I just set the maximum possible bounty on a Quantum Computing Stack Exchange problem. I could answer myself, but I know many others could too, and this seemed like fun. quantumcomputing.stackexchange.com/questions/40...
quantumcomputing.stackexchange.com
What is the complexity of modulo order-finding problem on classical computer?
It doesn't seem to be NP-complete. But has it been proved to be NP-hard?
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John Watrous @johnwatrous.bsky.social · 26/11/2024
Interesting but perhaps not exactly breaking (at least as a headline). Richard Jozsa argued, over 25 years ago, that "doing nothing" is an essential ingredient for quantum speed-ups: arxiv.org/abs/quant-ph...
arxiv.org
Quantum Effects in Algorithms
We discuss some seemingly paradoxical yet valid effects of quantum physics in information processing. Firstly, we argue that the act of ``doing nothing'' on part of an entangled quantum system is a hi...
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John Watrous @johnwatrous.bsky.social · 25/11/2024
I hereby take full credit for encouraging Olivia to use this platform. You're welcome, my work here is done. (But I'll continue to hang out.)
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John Watrous @johnwatrous.bsky.social · 24/11/2024
I may be an outlier, but I was never on Twitter myself. I decided to check out Bluesky specifically because Paul Krugman mentioned it in his piece on X in the NY Times: www.nytimes.com/2024/11/18/o...
nytimes.com
Opinion | The Dollar Still Has Its Mojo. X, Not So Much.
Ruining a network is hard, but Elon Musk shows it’s possible.
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John Watrous @johnwatrous.bsky.social · 24/11/2024
Yes, I've done exactly this many times! Sometimes it helps to crank up the precision and then head on over to the Inverse Symbolic Calculator to see what those numbers really are.
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John Watrous @johnwatrous.bsky.social · 24/11/2024
Because you're awesome and we want to hear what you have to say.
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John Watrous @johnwatrous.bsky.social · 24/11/2024
I poured my cruelty, malice, and will to dominate all life into that thing. Starting to feel the itch to write a new edition — but not just yet.
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