Henry Yuen

@henryyuen.bsky.social

Complexity, in all its forms. Associate Professor of Computer Science at Columbia University. http://www.henryyuen.net

5/ My and others' first reaction was that the paper is not well written. I've changed my mind on that. I spent >1hr on just the ~1-page proof overview. It is 𝐝𝐞𝐧𝐬𝐞 and 𝐭𝐞𝐫𝐬𝐞. It lacks helpful framing, but all key ideas are there. The paper's body is quite accessible!

"We're all worried," as what it means to do research (in my field, Theoretical CS) seems to be shifting, and shifting fast. What to do? Senior researchers must lead by example, knowing that not everything will pan out. What I'm suggesting below may not work everywhere, but here's my own advice: 1/

Some initial thoughts, and a complicated mix of feelings. Wow. I mean, Erdos problems are cool (I genuinely mean that), I didn't know about the Jacobian conjecture before it got disproved. But this newest batch from OpenAI hits home in a way the previous announcements did not.

In this MURI project with Sebastian Will (Columbia), Yongshan Ding (Yale), Shruti Puri (Yale), and Daniel Grier (UCSD), we will explore the potential uses and benefits (and limitations!) of using quantum gates that can act on many qubits at a time.

The Data Science Institute at Columbia University@datascicolumbia.bsky.social · 4mo ago

Led by DSI member @henryyuen.bsky.social, a new multi-university grant from the Air Force Office of Scientific Research (AFOSR) will examine whether larger quantum operations could reduce errors and make future quantum computers more practical. More: datascience.columbia.edu/news/2026/tr...

I discuss fully quantum complexity theory with @benbenbrubaker.bsky.social. Although we're not really sure, it seems like our understanding of computing on quantum data needs new foundations. Transforming quantum data is less like solving a hard math problem, and more like doing an intricate dance.

Ben Brubaker@benbenbrubaker.bsky.social · 6mo ago

How can we make sense of computational problems that we don’t even have the language to describe? I spoke to @henryyuen.bsky.social about what’s missing from the standard approach to quantum complexity theory — read more in @quantamagazine.bsky.social!

My student @johnbostanci.bsky.social, Chinmay Nirkhe, Jonas Haferkamp, and Mark Zhandry have put out a tour-de-force paper that shows, relative to a classical oracle, QMA is stronger than QCMA -- i.e., quantum proofs >> classical proofs. Congratulations to the authors! arxiv.org/abs/2511.09551

Separating QMA from QCMA with a classical oracle

We construct a classical oracle proving that, in a relativized setting, the set of languages decidable by an efficient quantum verifier with a quantum witness (QMA) is strictly bigger than those decid...

arxiv.org

Tomorrow I am teaching quantum phase estimation in my Intro to Quantum Computing Class for the seventh time. I was prepared to teach it the standard, textbook, Nielsen and Chuang way: applied controlled unitaries and their powers thereof, apply inverse QFT to the ancillas.

How fast can (pseudo)random unitaries be implemented on a quantum computer? O(1) time suffices (provided you can do things like intermediate measurements)! This -and more- is thanks to a superfun collaboration with Ben Foxman, @nat-parham.bsky.social, and @franvasco.bsky.social (all PhD students!).

Francisca Vasconcelos@franvasco.bsky.social · 12mo ago

In exciting new work with Ben Foxman, @nat-parham.bsky.social , and @henryyuen.bsky.social we show that t-designs and pseudorandom unitaries are implementable in constant (quantum) time! arxiv.org/abs/2508.11487

One of the great joys of 2025 (so far) has been learning about nonlocal quantum computation. It's an astonishingly interesting playground of ideas. In this fun collaboration with @hippoquantus.bsky.social, Simon, Alex, Mikka, and Philip, we uncover some hidden structure in this playground.

Andreas Bluhm@hippoquantus.bsky.social · last yr.

We have a new preprint out on the topic of quantum position verification and non-local quantum computation (NLQC): scirate.com/arxiv/2505.2.... We are comparing different NLQC tasks and find reductions between them (in the sense of if I can do task 1, then I can do task 2 with an extra EPR pair).