Theoretical physicist @Caltech, Director of @IQIM_Caltech
Pasadena, California
- Tweets 6,065
- Following 1,017
- Followers 281,475
- Likes 5,824
The audio recordings of the Feynman Lectures on Physics (1961-64) are now publicly available.
Don't be discouraged by the quality of the recording of Lecture #1, which is damaged. The quality of the rest is pretty good.
feynmanlectures.caltech.edu/…
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My lectures from the first term of our quantum computing course @Caltech have been posted on YouTube. Slides for all lectures are also available.
piped.video/playlist?list=PL…
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Congratulations, @RobertHuangHY, who defended his PhD thesis today. I've learned so much from you!
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Stephen Hawking 1942-2018. A great physicist, of course, and also a great man who inspired millions. I'll remember the sharp wit and twinkling eyes; he never took himself too seriously. His friends will miss him terribly.
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Steven Weinberg 1933-2021. One of the most accomplished scientists of our age, and a particularly eloquent spokesperson for the scientific worldview. Steve remained intellectually active to the end. An immeasurable loss.
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Group photo for the 28th Solvay Conference on Physics: The Physics of Quantum Information.
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I'm excited and honored to receive the 2024 Bell Prize.
cqiqc.physics.utoronto.ca/ne…
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Today is World Quantum Day. Let’s all try to be coherent.
worldquantumday.org/
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The pioneering work of Clarke, Devoret, and Martinis showed that very cold electrical circuits behave in ways that exhibit fundamental principles of quantum physics. Building on this achievement, Devoret, Martinis, and many others are constructing quantum computers, powerful tools for exploring quantum science and solving very hard computational problems. Congratulations!
BREAKING NEWS
The Royal Swedish Academy of Sciences has decided to award the 2025 #NobelPrize in Physics to John Clarke, Michel H. Devoret and John M. Martinis “for the discovery of macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit.”
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Someone asked: What are the most important ideas in physics over the past 30 years? Three immediately came to mind: The holographic principle, topological order, quantum error correction. What's lovely is that these three ideas are so closely related.
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From her 1993 PhD Thesis @Caltech: "I dedicate this thesis to all the women scientists I have known."
Andrea Ghez is a superb spokesperson for science --- no doubt she will be an inspiring role model to many future scientists.
“I hope I can inspire other young women into the field. It’s a field that has so many pleasures, and if you are passionate about the science, there’s so much that can be done.”
- Andrea Ghez speaking at today’s press conference where her #NobelPrize in Physics was announced.
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I have news. Starting now I will be an Amazon Scholar, working one day per week at the AWS Center for Quantum Computing in Pasadena. We have an outstanding team, and I’m very excited to join. I will also continue as a full-time professor @Caltech and Director of @IQIM_Caltech. /1
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100 years ago, Stern and Gerlach measured a qubit.
When was quantum spin discovered?
#otd exactly 100 years ago, Otto Stern and Walther Gerlach made what would become one of the most iconic observations in the history of physics: a magnetic field split a beam of silver atoms neatly into two beams
scientificamerican.com/artic…
ALT Image from Issachar Unna and Tilman Sauer, Ann. Phys. 525, A15-A19 (2013)
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Quantum science and technology is exciting when discussed accurately and responsibly. It's disappointing that @TIME would publish such a misleading article.
TIME's new cover: Quantum computers will transform our world—and create a 21st century "space race" ti.me/3j2McaL
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I was asked by Tony Hey to contribute a chapter for a new edition of the Feynman Lectures on Computation. All I had to do (in about 40 pages) is explain what’s happened in quantum computing since Feynman first talked about it 40 years ago.
arxiv.org/abs/2106.10522
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Congratulations to three visionary pioneers of quantum information science!
BREAKING NEWS:
The Royal Swedish Academy of Sciences has decided to award the 2022 #NobelPrize in Physics to Alain Aspect, John F. Clauser and Anton Zeilinger.
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Overheard: "Qubits are like children --- it's better to have a few high-quality ones than a bunch of noisy ones."
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Renormalization, writes David Tong, a theorist at the University of Cambridge, is “arguably the single most important advance in theoretical physics in the past 50 years.”
I agree! Ken Wilson "changed physics forever."
quantamagazine.org/how-renor…
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Aside from Yang-Mills theory and parity nonconservation, Yang made so many profound contributions to physics! One that deeply impressed me as I was starting grad school: a 1975 paper with T. T. Wu highlighting the role of fiber bundles in gauge theory.
nytimes.com/2025/10/18/scien…
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I’m so proud of @RobertHuangHY, who received the Clauser Prize @Caltech for his PhD thesis “Learning in the Quantum Universe,” which was judged “to have the greatest potential to open new avenues of human thought and endeavor.” #Caltech2024
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You’re going to think I’m kidding, but we tried them both, and the one on the left gets the dishes cleaner. #QuantumAdvantage
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When and how will quantum computing broadly benefit humanity? Despite exhilarating recent progress, we still don’t know. Here my friend Jens Eisert and I assess the current status and the challenges ahead. We are optimistic about the quantum future, but there’s a lot of work to do.
arxiv.org/abs/2510.19928
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Wisdom from Scott Aaronson (1/2): “I think presenting to the public or to investors that we know how to get big quantum speed-ups for machine learning and optimization in the near future is fundamentally dishonest.”
politico.com/newsletters/dig…
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“The Physics of Quantum Information” -- My overview talk at the 28th Solvay Conference on Physics (May 2022). One could say a lot more, but my goal was to be succinct.
arxiv.org/abs/2208.08064
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In their roadmap, Microsoft described a protocol for demonstrating a topologically protected qubit. There is no publicly available evidence that this test has been conducted successfully. I hope we will hear more soon.
arxiv.org/abs/2502.12252
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Fantastic news! Bennett, Brassard, Deutsch, and Shor share the Breakthrough Prize in Fundamental Physics for “foundational work in the field of quantum information.”
scientificamerican.com/artic…
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Jeff Kimble 1949-2024. An extraordinary pioneer of quantum information science and a great friend who inspired me in many ways. Jeff's wise counsel made me a better scientist and a better person.
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Murray Gell-Mann 1929-2019. A prodigious intellect and an extraordinarily influential theoretical physicist. Strangeness, the renormalization group, V-A theory, SU(3) symmetry, quarks ... This and much more we owe to Murray. It's a sad day @Caltech and for the world of physics.
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Jim Bardeen 1939-2022. Unassuming and brilliant, like his father and brother. Perhaps best known for formulating the laws of black hole mechanics (with Carter and Hawking) and his gauge-invariant analysis of cosmological perturbations. He'll be missed.
nytimes.com/2022/07/03/scien…
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Edward Witten: "... what I regard as the most exciting development in the last six or seven years, even a little more, is the role of quantum information theory in gravity. So, I'm looking for a way to become involved there ..."
Ed Witten of @the_IAS describes his interest in #quantuminformation, the work of @gthooft in gauge theory and his entree to string theory, current algebra with Steve Weinberg, the origin of M-theory, and what it means to make peace with the #multiverse
aip.org/history-programs/nie…
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An @edX course on quantum information science, taught by two of the world's leading experts: Isaac Chuang and Peter Shor. Starts January 14.
edx.org/course/quantum-infor…
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There is a lot of wisdom in this piece by David Stern. I reread it from time to time to remind myself.
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I'm excited for the recipients of the Nobel Prize in Physics, especially @Caltech alum Andrea Ghez (PhD '93). But it's also a poignant moment. I'm thinking of how much Stephen Hawking would have enjoyed sharing a Prize for advances in General Relativity.
BREAKING NEWS:
The Royal Swedish Academy of Sciences has decided to award the 2020 #NobelPrize in Physics with one half to Roger Penrose and the other half jointly to Reinhard Genzel and Andrea Ghez.
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"Gravity, in particular, doesn’t fit into the framework of quantum mechanics like our other theories do. It’s possible — maybe even perfectly reasonable — to imagine that our inability to understand quantum mechanics itself is standing in the way."
nytimes.com/2019/09/07/opini…
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A fitting honor for "Amazing Grace" Hopper, trailblazing computer scientist. Well done, @Yale! #WomeninScience news.yale.edu/2017/02/11/yal…
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One less thing to worry about: in classical general relativity, slowly rotating black holes struck by gravitational waves are stable. It's a milestone achievement in the theory of gravitation. Congratulations to the authors, and their predecessors.
quantamagazine.org/black-hol…
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I was thrilled to hear about the surface code when Alexei Kitaev visited @Caltech in April 1997. It's heartening to see the hardware catching up with the theory of quantum error correction. There's still far to go but encouraging progress @GoogleQuantumAI.
quantamagazine.org/quantum-c…
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45 years ago today, I married Roberta, my best friend and the love of my life.
In the photo I'm telling the world all about it exactly 5 years ago.
And I love her more and more every day.
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I often marvel at how @PeterShor1 achieved three major breakthroughs in consecutive years. Quantum algorithms for factoring and discrete log in 1994, quantum error-correcting codes in 1995, schemes for quantum fault tolerance in 1996. Astonishing.
quantamagazine.org/how-quant…
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My secret formula for scientific success: Wonderful students and postdocs who teach you far more than you could teach them.
quantumfrontiers.com/2024/02…
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My debut column for @QuantaMagazine is about quantum supremacy.
quantamagazine.org/john-pres…
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Everything you always wanted to know about QCD? At any rate, an extraordinary document.
arxiv.org/abs/2212.11107
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A lot of smart folks worked hard and long on this paper. I’m proud to be part of such an excellent team @awscloud. 1/4
arxiv.org/abs/2012.04108
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Urmila Mahadev's determination to show that a classical computer can check a quantum computer's output finally paid off. What kept her going? “I was spending time learning about things that I was interested in, so it couldn’t really be a waste of time.”
quantamagazine.org/graduate-…
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Alex Zlokapa, then an undergrad @Caltech, used classical machine learning to make Alexei Kitaev's toy model of quantum gravity simple enough to simulate using 9 qubits in an existing quantum computer.
quantamagazine.org/physicist…
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Freeman Dyson 1923-2020. An extraordinarily influential scientist, a brilliant writer, a delightful colleague. We welcomed him @Caltech most recently when he joined the Feynman 100 celebration in 2018.
nytimes.com/2020/02/28/scien…
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By popular demand, a short thread with a bit more explanation.
Someone asked: What are the most important ideas in physics over the past 30 years? Three immediately came to mind: The holographic principle, topological order, quantum error correction. What's lovely is that these three ideas are so closely related.
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Yuri Manin 1937-2023. Already in 1980, Manin emphasized the apparent exponential cost of simulating a many-particle particle system using a classical computer, and noted the potentially profound implications for computational complexity theory.
en.wikipedia.org/wiki/Yuri_M…
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A long read but worth the time.
quantumfrontiers.com/2023/06…
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Jonathan Dowling 1955-2020. Jon was a prolific scientist, a nurturing mentor, and a uniquely exuberant personality. In the photo we admire Jon's license plate during my visit to LSU in 2019.
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For my freshman seminar @Caltech, it might be fun for the class to discuss some provocative essays relating to quantum science. Here are a few that come to mind. (Some may be too technical but we could read excerpts.) What should be added to or subtracted from this list?
Feynman, Plenty of room at the bottom
Wigner, The unreasonable effectiveness of mathematics in the natural sciences
Weisskopf, Of atoms, mountains, and stars
Anderson, More is different
Mermin, Quantum mysteries for anyone
Feynman, Simulating physics with computers
Zurek, Decoherence and the transition from quantum to classical
Aaronson, NP-complete problems and physical reality
Coleman, Quantum mechanics in your face
Aaronson, Quantum randomness
Aharonov and Vazirani, Is quantum mechanics falsifiable?
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I, too, learned as a student that a particle is a unitary irreducible representation of the Poincare group. I was immediately drawn to this idea, both for its mathematical elegance and because it seemed so a priori unlikely.
Everything in the universe reduces to elementary particles. So, I set out to address the question: What are particles? The reporting took me to the frontier of fundamental physics.
Before you read, would love to hear your best tweet-length definition!
quantamagazine.org/what-is-a…
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Raymond Laflamme 1960-2025. A great scientist, renowned for his pioneering contributions to quantum error correction. A great leader, founding director of @QuantumIQC. A great colleague and teacher whose legacy continues to inspire us.
uwaterloo.ca/institute-for-q…
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Roger Penrose is a visual thinker. His "tendency to work through mathematics with the aid of a mental image has contributed to some of his most important breakthroughs, including his Nobel-winning work on black holes."
spectator.co.uk/article/a-si…
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"Now, physicists at the University of Innsbruck have built a prototype of an ion trap quantum computer that can be used in industry. It fits into two 19-inch server racks like those found in data centers throughout the world."
phys.org/news/2021-06-compac…
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"Many-body quantum entanglement has simultaneously emerged as an organizing principle in both [high-energy and condensed-matter physics]."
nature.com/articles/s42254-0…
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Applicants to @Caltech Physics PhD program name their preferred research areas. This year's breakdown of theorists:
21% Condensed Matter/Atomic/Molecular
20% Quantum Information
16% Elementary Particles
15% String Theory
13% Gravitation
7% Cosmology
6% Astrophysics
2% Other
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Here it is! Video of today's talk @IQIM_Caltech
by John Martinis on "Quantum supremacy using a programmable superconducting processor." It was a great talk, and we're pleased that John chose to give the first public seminar on this topic @Caltech.
piped.video/FklMpRiTeTA
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Our hill is burnt and our house smells smoky, but it’s great to be home after a 3.5-day mandatory evacuation. We’re deeply grateful to the firefighters who saved our neighborhood, and our friends who offered to help. #BobcatFire
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The AWS Center for Quantum Computing @Caltech is proud to announce the realization of a hardware-efficient repetition cat code in a superconducting device. /1
arxiv.org/abs/2409.13025
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I signed this petition. ICE announced that international students attending US universities offering online-only classes in the fall due to COVID-19 must leave the country. This deserves more media attention.
petitions.whitehouse.gov/pet…
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Useful perspective, clearly written and well-reasoned.
arxiv.org/abs/2501.05694
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A few notable questions discussed at the 28th Solvay Conference on Physics: (Far from complete list!)
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Good crowd for our session at #apsmarch celebrating 30 years since Shor’s algorithm!
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I'm listening to a student giving a presentation, who, speaking of Maldacena's 1997 paper, remarks in passing: "That was before I was born." A factually true statement, but somehow it scared me a little.
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“Perhaps kids who grow up playing quantum games will acquire a visceral understanding of quantum phenomena that our generation lacks.”
quantumfrontiers.com/2024/08…
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If you are interested in quantum computing, I strongly recommend this insightful article by @Caltech student @robbieking1000 calling for a "scrappier approach" to finding new applications.
quantumfrontiers.com/2025/04…
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"To summarize, we conclude that there is no indication that quantum machine learning will substantially improve supervised learning on classical datasets."
🧐 Can Quantum Machine Learning Models outperform classical ML models?
We worked on a few steps towards answering this question: arxiv.org/abs/2106.03747
with Simon Buchholz and @bschoelkopf
a Thread 📜 1/8
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I'm in Brussels, where the 28th Solvay Conference on Physics begins tomorrow. For the first time ever, the theme of the conference is "The Physics of Quantum Information." I'm looking forward to exciting discussions with esteemed colleagues.
solvayinstitutes.be/html/sol…
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Philip Anderson 1923-2000. One of history's greatest physicists (from the Anderson-Higgs mechanism, to localization, to quantum spin liquids, and beyond), he taught us that "More is Different."
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Scott weighs in on reports that Google has achieved quantum supremacy.
scottaaronson.com/blog/?p=43…
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“Back in the '60s, we used to invest a little over 2% of our entire [gross domestic product] in pure research and investments in science. Today, it's 0.7%. I am going to change that. We are going to change that,” Biden said.
1/2
nextgov.com/cio-briefing/202…
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If you are curious about the exciting recent progress on the black hole information puzzle, but don't want to wade into a lot of technical details, this review is a very good place to start.
Here's a review we wrote on recent progress on the information paradox. It's geared towards non-specialists, though undergrad physics knowledge is assumed. No knowledge (or brains) is needed for the last paragraph though, and we apologize in advance... arxiv.org/abs/2006.06872
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I am delighted to hear that a Special Breakthrough Prize has been awarded to Steve Weinberg, by PhD advisor and scientific hero. No one could be more deserving. Congratulations, Steve!
A Special Breakthrough Prize in Fundamental Physics has been awarded to Steven Weinberg @UTAustin, a key architect of the Standard Model, and a hugely influential educator, communicator and advocate of science for well over half a century. breakthroughprize.org/News/6…
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It's wonderful to see Alexei receive this honor, so well deserved and long overdue. His contributions to both condensed matter and quantum information have been truly astonishing in both scope and depth. Congratulations!
Congratulations to Alexei Y. Kitaev of @Caltech who has been elected to the National Academy of Sciences for his contributions to condensed matter physics. #NAS158 Read more: ow.ly/VnQd50Ey3fa
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Fond memories of Steve Weinberg from Helen Quinn, Mark Raizen, Raphael Flauger, Gerry Gilbert, and me.
physicstoday.scitation.org/d…
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6,100 neutral-atom qubits trapped in a grid by lasers @Caltech ... is a lot.
caltech.edu/about/news/calte…
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Scott Aaronson remembers Steve Weinberg. Touching and insightful.
scottaaronson.com/blog/?p=55…
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"The future ain't what it used to be."
Wow, @preskill just posted a new paper! Will this be the next trend after NISQ and quantum supremacy?
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Ouch! Suspension of the H-1B visa program, even if temporary, is a very painful blow to US science and the tech industry.
washingtonpost.com/immigrati…
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“It took us 40 years in math to make sense of four pages [by Polyakov]”
40 years ain't bad.
quantamagazine.org/mathemati…
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10 years of the Higgs boson. Lots of beautiful data since then, but physics beyond the standard model remains frustratingly elusive. A good review.
nature.com/articles/s41586-0…
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Juan Maldacena
Says spacetime is emergent.
Emergent from what?
#QuantumHaiku
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Congratulations @PeterShor1, recipient of the 2025 Claude E. Shannon Award "for consistent and profound contributions to the field of information theory"!
itsoc.org/news/shannon-award…
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From Chris Monroe @IonQ_Inc:
"The big quantum computing discoveries that will most impact society are still years away. In the meantime ... too much hype risks disillusionment that may slow the progress."
Amen.
venturebeat.com/2019/04/21/q…
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In this paper with @RobertHuangHY and Richard Kueng, we compare quantum and classical machine learning for predicting outcomes of quantum experiments. /1
arxiv.org/abs/2101.02464
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For those who celebrate, November 7 is the birthday of two scientific giants: Marie Curie (1867-1934) and Lise Meitner (1878-1968), justly renowned for their world-changing investigations of radioactivity and nuclear fission.
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Well-informed comments from Jason Alicea about today's Microsoft Quantum announcement:
Jason Alicea, a professor of theoretical physics at the California Institute of Technology, questioned whether the company had actually built a topological qubit, saying the behavior of quantum systems is often hard to prove.
“A topological qubit is possible in principle, and people agree it is a worthwhile goal,” Dr. Alicea said. “You have to verify, though, that a device behaves in all the magical ways that theory predicts it should; otherwise, the reality may turn out to be less rosy for quantum computing. Fortunately, Microsoft is now set up to try.”
nytimes.com/2025/02/19/techn…
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We lost Marjie yesterday. She was 14, and had a very happy life. We'll remember the good times --- the joy she brought us every day --- and we'll always miss her.
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Stephen Hawking would have been 70 years old today. We're still struggling with the deep implications of his greatest discovery --- that black holes emit thermal radiation. I miss the twinkle in his eye.
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I wrote up my recent talk about prospects for near-term applications of quantum computers. Here's the short version: Quantum technology is making exciting progress, but let's not expect too much too soon.
arxiv.org/abs/1801.00862
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