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Ryuji Takagi

@ryujitakagi.bsky.social

Associate professor at the University of Tokyo. Quantum information. https://ryujitakagi.wordpress.com/

6 Posts37 Follower27 Folgt
Ryuji Takagi@ryujitakagi.bsky.social · 11mo ago

Posted a joint work with Naoto Shiraishi on quantum thermodynamics. We managed to characterize the state transformability (for general coherent states!) with a correlated catalyst by the single free energy ordering. arxiv.org/abs/2510.05642

Recovery of the second law in fully quantum thermodynamics

Quantum thermodynamics investigates how robust the second law of thermodynamics serves as the unique fundamental law in the small quantum world. To tackle this problem, the quantum coherence constitut...

arxiv.org

Ryuji Takagi@ryujitakagi.bsky.social · 12mo ago

Posted our work on Uhlmann transformation, where we provided its algorithmic implementation. As an application, we improved on the prior state-of-the-art cost for fidelity estimation in purified access model. Joint work with Takeru Utsumi, Yoshifumi Nakata, and Qisheng Wang. arxiv.org/abs/2509.03619

Quantum algorithms for Uhlmann transformation

Uhlmann's theorem is a central result in quantum information theory, associating the closeness of two quantum states with that of their purifications. This theorem well characterizes the fundamental t...

arxiv.org

Jeongrak Son@perp-waterfall.bsky.social · last yr.

Our paper (w/ Marek, @ryujitakagi.bsky.social, @nellynghy.bsky.social ) on Quantum Dynamic Programming has recently been published in PRL: journals.aps.org/prl/abstract... Xin Yi from CQT wrote a great highlight article for this paper: www.cqt.sg/highlight/20...

Quantum Dynamic Programming

We introduce a quantum extension of dynamic programming, a fundamental computational method that efficiently solves recursive problems using memory. Our innovation lies in showing how to coherently ge...

journals.aps.org

Ryuji Takagi@ryujitakagi.bsky.social · last yr.

Our work on quantum thermodynamics has been published in PRL. We showed that Gibbs-preserving operations may incur infinite costs to implement, prompting us to reconsider the physical justification of their use. Joint work with Hiroyasu Tajima. journals.aps.org/prl/abstract...

Gibbs-Preserving Operations Requiring Infinite Amount of Quantum Coherence

Gibbs-preserving operations have been studied as one of the standard free processes in quantum thermodynamics. Although they admit a simple mathematical structure, their operational significance has b...

journals.aps.org

Ryuji Takagi@ryujitakagi.bsky.social · last yr.

Posted a preprint with @kaitowatanabe.bsky.social on quantum thermo. We introduced a "universal work extractor", which is designed independently of the input state but still extracts the optimal work from every input state given in the iid form. arxiv.org/abs/2504.12373

Universal work extraction in quantum thermodynamics

Evaluating the maximum amount of work extractable from a nanoscale quantum system is one of the central problems in quantum thermodynamics. Previous works identified the free energy of the input state...

arxiv.org