Ryuji Takagi
@ryujitakagi.bsky.social
Associate professor at the University of Tokyo. Quantum information.
https://ryujitakagi.wordpress.com/
https://ryujitakagi.wordpress.com/
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
October 9, 2025 at 1:20 AM
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
The next quantum resources workshop happens in Tokyo! Looking forward to seeing many of you there!
2026.quantumresources.science
Submission deadline: 31 October 2025
Workshop: 16–20 March 2026
2026.quantumresources.science
Submission deadline: 31 October 2025
Workshop: 16–20 March 2026
Quantum Resources workshop 2026
The workshop "Quantum Resources 2026" will take place in Tokyo, Japan in March. Submissions welcome!
2026.quantumresources.science
October 6, 2025 at 7:35 AM
The next quantum resources workshop happens in Tokyo! Looking forward to seeing many of you there!
2026.quantumresources.science
Submission deadline: 31 October 2025
Workshop: 16–20 March 2026
2026.quantumresources.science
Submission deadline: 31 October 2025
Workshop: 16–20 March 2026
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
September 5, 2025 at 7:08 AM
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
Reposted by Ryuji Takagi
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...
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
May 21, 2025 at 8:54 AM
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...
Xin Yi from CQT wrote a great highlight article for this paper: www.cqt.sg/highlight/20...
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
April 30, 2025 at 2:44 PM
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...
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
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
April 18, 2025 at 1:25 PM
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
arxiv.org/abs/2504.12373
Reposted by Ryuji Takagi
Kaito Watanabe "Black box work extraction and composite hypothesis testing" #QuantumResources2025
Glad to learn about these results. I'll likely adapt my talk for Thursday a bit based on what I learned.
Glad to learn about these results. I'll likely adapt my talk for Thursday a bit based on what I learned.
March 18, 2025 at 12:15 AM
Kaito Watanabe "Black box work extraction and composite hypothesis testing" #QuantumResources2025
Glad to learn about these results. I'll likely adapt my talk for Thursday a bit based on what I learned.
Glad to learn about these results. I'll likely adapt my talk for Thursday a bit based on what I learned.