Felix Leditzky

Research

My research focuses on quantum information theory, in particular the mathematical and computational aspects of quantum Shannon theory. Below is a list of topics that I am particularly interested in, together with some selected papers I worked on. More information on my papers can be found in the next section.

• Information theory: Quantum channel capacities, superadditivity in quantum information science, stabilizer formalism, quantum source coding, data processing inequalities, strong converse theorems, second order asymptotics, classical network information theory.
  Selected papers:
  • The platypus of the quantum channel zoo (2022)
  • Generic nonadditivity of quantum capacity in simple channels (2022)
  • Playing Games with Multiple Access Channels (2019)
  • Quantum and private capacities of low-noise channels (2017)
• Mathematical methods: Group theory, representation theory, commutative algebra, matrix analysis, trace and operator inequalities.
  Selected papers:
  • Optimality of the pretty good measurement for port-based teleportation (2020)
  • Error Thresholds for Arbitrary Pauli Noise (2019)
  • Asymptotic performance of port-based teleportation (2018)
  • Data processing for the sandwiched Rényi divergence: a condition for equality (2016)
• Physics: Many-body quantum systems, tensor networks, multipartite entanglement.
  Selected papers:
  • Adaptive estimation of quantum observables (2021)
  • Quantum Codes from Neural Networks (2018)
• Optimization theory: convex optimization (in particular semidefinite programming and geometric programming), global optimization techniques, neural networks.
  Selected papers:
  • On the separation of correlation-assisted sum capacities of multiple access channels (2022)
  • Quantum Codes from Neural Networks (2018)
  • Useful states and entanglement distillation (2017)

Papers

Below is a list of my most recent papers, including both preprints and published articles. For a full list, see arXiv.org, Google Scholar, or my CV.

Recent preprints

• E. Chitambar, F.L.:
  "On the Duality of Teleportation and Dense Coding"
  arXiv preprint, arXiv:2302.14798 [quant-ph], 2023.
• A. Seshadri, F.L., V. Siddhu, G. Smith:
  "On the separation of correlation-assisted sum capacities of multiple access channels"
  arXiv preprint, arXiv:2205.13538 [cs.IT], 2022.
• F.L., D. Leung, V. Siddhu, G. Smith, J.A. Smolin:
  "Generic nonadditivity of quantum capacity in simple channels"
  arXiv preprint, arXiv:2202.08377 [quant-ph], 2022.

Recent published papers

• F.L., D. Leung, V. Siddhu, G. Smith, J.A. Smolin:
  "The platypus of the quantum channel zoo "
  IEEE Transactions on Information Theory, 2023. arXiv:2202.08380
• A. Shlosberg, A.J. Jena, P. Mukhopadhyay, J.F. Haase, F.L., L. Dellantonio:
  "Adaptive estimation of quantum observables"
  Quantum 7, 906, 2023. arXiv:2110.15339 [quant-ph]
• F.L.:
  "Optimality of the pretty good measurement for port-based teleportation"
  Letters in Mathematical Physics 112(98), 2022. arXiv:2008.11194 [quant-ph]
• C. Hirche, F.L.:
  "Bounding quantum capacities via partial orders and complementarity"
  IEEE Transactions on Information Theory 69(1), pp.283-297, 2022. arXiv:2202.11688 [quant-ph]
• R. Arnon-Friedman, F.L.:
  "Upper bounds on device-independent quantum key distribution rates and a revised Peres conjecture"
  IEEE Transactions on Information Theory 67(10), pp.6606-6618, 2021. arXiv:2005.12325 [quant-ph]
• J. Bausch, F.L.:
  "Error Thresholds for Arbitrary Pauli Noise"
  SIAM Journal on Computing 50(4), pp.1410-1460, 2021. arXiv:1910.00471 [quant-ph]
• E.I. Rosenthal, C.M.F. Schneider, M. Malnou, Z. Zhao, F.L., B.J. Chapman, W. Wustmann, Z. Ma, D.A. Palken, M.F. Zanner, L.R. Vale, G.C. Hilton, J. Gao, G. Smith, G. Kirchmair, K.W. Lehnert:
  "Efficient and low-backaction quantum measurement using a chip-scale detector"
  Physical Review Letters 126(9), 090503, 2021. arXiv:2008.03805 [quant-ph]
• M. Christandl, F.L., C. Majenz, G. Smith, F. Speelman, M. Walter:
  "Asymptotic performance of port-based teleportation"
  Communications in Mathematical Physics 381, 379-451, 2021. arXiv:1809.10751 [quant-ph]
• F.L., M. Alhejji, J. Levin, G. Smith:
  "Playing Games with Multiple Access Channels"
  Nature Communications 11, 1497, 2020. arXiv:1909.02479 [quant-ph]
• J. Bausch, F.L.:
  "Quantum Codes from Neural Networks"
  New Journal of Physics 22, 023005, 2020. arXiv:1806.08781 [quant-ph]
• F.L., D. Leung, G. Smith:
  "Dephrasure channel and superadditivity of coherent information"
  Physical Review Letters 121(16), 160501, 2018. arXiv:1806.08327 [quant-ph]

At this point I want to plug the awesome python script arxiv-collector written by D.J. Sutherland. This script generates a .tar.gz archive of your latex project that can be uploaded to the arXiv, avoiding in particular any version mismatches between your local biblatex installation and the one on the arXiv servers. It continues to save me a lot of time at each arXiv submission!

Talks

Below you can find links to slides, videos and files for a selection of talks and posters I have presented at conferences and seminars. For a full list of conference and seminar talks and posters, see my full CV.

For the slides of my more recent presentations, I am explaining my workflow and what software I am using in this Twitter thread.

• Symmetries and asymptotics of port-based teleportation
  [slides] presented at Quasar Seminar, University of Ottawa, Mar 2021.
  [slides] [video] presented at Tutte Colloquium, Department of Combinatorics and Optimization, University of Waterloo, Jul 2020.
• Playing games with multiple access channels
  [slides] [video] presented at TQC 2020, Riga, Latvia, Jun 2020 (conference held online).
  [slides] presented at ICTQT Seminar, University of Gdansk, Apr 2020.
  [video] presented at QuICS Seminar, University of Maryland, Nov 2019.
• Error thresholds for arbitrary Pauli noise
  [slides] [video] long talk presented as an extended talk at Beyond IID 2020, Stanford, CA, Nov 2020.
  [slides] [video] short talk presented at QIP 2020, Shenzhen, China, Jan 2020.
• Quantum codes from neural networks
  [slides] presented at Beyond IID 2019, Sydney, Australia, Jul 2019.
  [slides] presented at IQC quantum innovators conference, University of Waterloo, Oct 2018.
• Asymptotic performance of port-based teleportation
  [slides] [video] presented at Banff meeting on resource theories, Jul 2019.
  [poster] presented at Beyond IID 2018, Cambridge, UK, Jul 2018.
• Dephrasure channel and superadditivity of coherent information
  [slides] presented at SquInT 2019, Albuquerque, USA, Feb 2019.
  [slides] presented at Beyond IID 2018, Cambridge, UK, Jul 2018.
• Quantum and private capacities of low-noise channels
  [slides] presented at IEEE ITW, Kaohsioung, Taiwan, Nov 2017.
  [poster] presented at QIP 2017, Delft, Netherlands, Jan 2018.
• Useful states and entanglement distillation
  [slides] presented at Beyond IID 2017, Singapore, Jul 2017.
• Strong converse theorems using Rényi entropies
  [poster] presented at QIP 2017, Seattle, USA, Jan 2017.
• Relative entropies and their use in quantum information theory
  [slides] presented at JILA group meeting, CU Boulder, Mar 2017.
• Equality condition in the data processing inequality for the quantum relative entropy
  [slides] presented at CAKE Seminar, University of Cambridge, Feb 2016.

Teaching

I have taught the courses below at the University of Illinois at Urbana-Champaign.

• Spring term 2023: Math 595 Quantum channels
• Fall term 2022: Math 595 Representation-theoretic methods in quantum information theory
• Fall term 2021: Math 416 Abstract Linear Algebra
• Spring term 2021: Math 595 Quantum channels I: Representations and properties
• Spring term 2021: Math 595 Quantum channels II: Data-processing, recovery channels, and quantum Markov chains

Misc

Useful links and references

• I'm in the process of compiling lists of references to topics in mathematics and quantum information science close to my own research. These lists are mainly intended for students who are either interested in working with me, or just want to learn more about these topics for their own research.
• I have compiled a list of some essential papers in quantum information theory from a survey among colleagues on Twitter.

Editorial service

• Quantum: the open journal for quantum science
  I have recently joined the journal Quantum as an editor, handling submissions in quantum information theory, quantum Shannon theory, and papers focusing on mathematical methods in quantum information theory. Quantum is a so-called arXiv overlay journal, and grants complete open access to all its published papers. Please consider submitting your papers on the above topics to Quantum!
• Illinois Journal of Mathematics
  I'm also a member of the editorial board of the Illinois Journal of Mathematics (IJM). IJM is a peer-reviewed journal with a rich history covering all areas of mainstream mathematics. Please consider submitting your paper on mathematical topics in quantum information theory to IJM!

Conference & workshop organization

I have acted as an organizer for the following conferences and workshops:

• TQC 2022, July 11-15, 2022, University of Illinois at Urbana-Champaign.
  Organized together Eric Chitambar, Emily Edwards, Kelly C. Foster, Kim Gudeman.
• QIP 2019, January 14-18, 2019, University of Colorado Boulder.
  Organized together with Graeme Smith.
• Rocky Mountain Summit on Quantum Information, June 25-29, 2018, JILA, University of Colorado Boulder.
  Organized together with Mark M. Wilde and Graeme Smith.

About me

Short CV

Jan 2021 to present

Assistant Professor

Department of Mathematics, University of Illinois at Urbana-Champaign

Dec 2019 to Dec 2020

Postdoctoral Fellow

Institute for Quantum Computing, University of Waterloo & Perimeter Institute for Theoretical Physics

Nov 2016 to Nov 2019

Postdoctoral Research Associate

JILA, University of Colorado Boulder

Oct 2013 to Oct 2016

PhD (Mathematics)

DPMMS, University of Cambridge [thesis]

Oct 2006 to Apr 2013

Diploma^† (Physics)

University of Vienna [thesis]

Oct 2006 to Feb 2012

Diploma^† (Mathematics)

University of Vienna [thesis]

^† Roughly equivalent to BSc+MSc.

Before joining UIUC, I held postdoctoral positions at the Institute for Quantum Computing at the University of Waterloo and Perimeter Institute for Theoretical Physics from Dec 2019 to Dec 2020, and at JILA at the University of Colorado Boulder from Nov 2016 to Nov 2019. I obtained my PhD from the University of Cambridge in 2016 with a thesis on Relative entropies and their use in quantum information theory. My academic journey started in my hometown Vienna, Austria, where I obtained diploma degrees (≈ BSc + MSc) in Mathematics and Physics. Here is a link to my full academic CV.

Personal

I was born in Vienna, Austria. In my spare time I like to play the guitar, read, listen to music, play and watch (European) football, get better at cooking, and travel. Actually, I'm interested in pretty much everything.

Contact

Email: <lastname>@illinois.edu

Postal address:
Office 39, Computing Applications Building
605 E Springfield Ave
Champaign, IL 61820
USA