Marco Tomamichel

A meme indicating how various objects in quantum information (pretty good measurement, Petz recovery map, Leifer-Spekkens state over time, and others) are shown to be fidelity/Bures projections in our article.

New preprint out with @marcotomamichel.bsky.social !

Projections with Respect to Bures Distance and Fidelity: Closed-Forms and Applications
scirate.com/arxiv/2602.1...

We derive simple closed-form solutions for fidelity / Bures/purified distance projections to various sets of interest.

The last defence this year 🥳💐 Congratulations to Hu Yanglin for successfully defending his thesis, "Quantum Oblivious Transfer: Bounds and Applications", on how to protect privacy with quantum technologies and how to learn quantum systems efficiently. He was advised by @marcotomamichel.bsky.social

Quantum Toolbox (12): Bretagnolle-Huber Inequality (1/6)

No, not really about publishing here, more about service work.

What would you do? Many senior academics seem to freeze and go straight ahead!

The twist: To go left, a lot of things need to come together. You need to walk to the other end of the trolley without getting distracted, passing through hundreds of passengers who all want something urgent from you. And once you are in the middle you can steer the trolley neither way.

3/3

-If you go right you would not do work you promised to do earlier, and hence admit that you took on too much to handle, and hope for understanding of your colleagues;
-If you go left, you would need to do the work yourself, which is clearly the morally right thing to do.

2/3

The senior academic trolley problem:

You can go straight ahead, but there is the career of a junior researcher on the track. Or you can go right or left to avoid any calamities.

1/3

Quantum Toolbox (10): Uhlmann's Theorem (1/6)

Please get in touch if you are interested in a PhD on the mathematics of quantum information and its applications to learning and communication.

Quantum Toolbox (9): Sample Complexity Lower Bounds via Mutual Information (1/6)

Congratulations to CQT Principal Investigator @marcotomamichel.bsky.social who has been awarded the prestigious National Research Foundation (NRF) Investigatorship. He receives support for a five-year programme of research starting in August 2025. buff.ly/QrAJWkn

🍾💐 Celebrating a successful thesis defence by Josep Lumbreras Zarapico!! 🍉🧀🍪 Advised by @marcotomamichel.bsky.social, Josep defended his thesis "Bandits Roaming Hilbert Space". He will next join Mile Gu’s group as a research fellow. Congrats and all the best, Dr Josep!

Quantum Toolbox (8): Hadamard's Three-Lines Theorem (1/6)

Meet a CQTian: Tristan Philippe - CQT - Centre for Quantum Technologies For French student Tristan, Singapore’s National Quantum Scholarship supports him to work on theoretical quantum cryptography

"I’m interested in how we create quantum primitives which ensure security of data," says Tristan Philippe, one of the first PhD students to start research at CQT under Singapore's National Quantum Scholarships Scheme 🇸🇬 🎓 Read his interview: bit.ly/3Zc95KK

🚨 Job alert 🚨
The group of Principal Investigator @ValerioScarani is looking for a Research Fellow! Find more information and apply here: t.co/PwKZfN6eTA

👏💐Congrats to PhD student Roberto Rubboli who successfully defended his thesis, "Optimization and Additivity of Quantum Relative Entropies"! He was advised by @marcotomamichel.bsky.social‬. Next, he will join the group of Daniel Stilck França at the University of Copenhagen. All the best Dr Roberto!

Quantum Toolbox (7): Continuity of the von Neumann Entropy (1/6)

Testing (Conditional) Mutual Information We investigate the sample complexity of mutual information and conditional mutual information testing. For conditional mutual information testing, given access to independent samples of a triple of ra...

We are happy to share our work in classical distribution testing "Testing (Conditional) Mutual Information" (arxiv.org/abs/2506.03894), which was recently accepted at COLT 2025. (1/6)

Quantum Toolbox (6): Hoeffding's Inequality (1/7)

Learning pure quantum states (almost) without regret We initiate the study of sample-optimal quantum state tomography with minimal disturbance to the samples. Can we efficiently learn a precise description of a quantum state through sequential measureme...

Our work "Learning pure quantum states (almost) without regret" (arxiv.org/abs/2406.18370) has received an important extension!

We connect the notion of regret with the disturbance caused by projective measurements to efficiently learn pure states (almost) without disturbance. (1/3)

Quantum Toolbox (5): Cauchy-Schwarz Inequality (1/6)

How to factor 2048 bit RSA integers with less than a million noisy qubits Planning the transition to quantum-safe cryptosystems requires understanding the cost of quantum attacks on vulnerable cryptosystems. In Gidney+Ekerå 2019, I co-published an estimate stating that 2048...

It's time we rename Q-Day to Gidney-Day.
arxiv.org/abs/2505.15917

Quantum Toolbox (4): Jordan's Lemma (1/6)

Quantum state-agnostic work extraction (almost) without dissipation:

We are excited to share a new application of the multi-armed quantum bandit framework—this time in quantum thermodynamics!

Submit your favorite, itch-to-scratch, drive-you-mad, want-to-see-solved open problems in learning theory to #COLT2025!

More info: learningtheory.org/colt2025/cfp...

⏰ Deadline: June 6 AoE

We were excited to host @christophhirche.bsky.social as an outgoing MSCA postdoc here in Singapore and are ready to host again whenever scientific interests align.

The larger-than-life Quantum Duel between Matthias Christandl and Gil Kalai will take place on Tuesday at 6:00 PM (CEST) in Prague.
www.learned.cz/en/activitie...
Watch the live stream here:
www.youtube.com/live/ykBkZB8...

Nice to see the university recognising not only ours but also our significant others’ contributions!