Aleks Kissinger
Aleks Kissinger
Biography
I am an Associate Professor of Quantum Computation. My research is in quantum information, quantum foundations, automated reasoning, category theory, graphical calculi, and graph rewriting. In particular, I am interested in applications of graphical languages to quantum circuit optimisation and the development of quantum causal models.
Papers
Selected publications can be found at the bottom of this page.
...including preprints and slides from some talks.
Research & Updates
 We're doing strong classical simulation of some pretty chunky quantum circuits (e.g. 50 qubits and 1400 T gates in < 5mins) using two kinds of magic: magic state decomposition and ZXcalculus magic. :)

Read a book, read a book...
Picturing Quantum Processes: A First Course in Quantum Theory and Diagrammatic Reasoning. Bob Coecke and Aleks Kissinger, Cambridge University Press
PQP, or "The Dodo Book", teaches quantum theory from the ground up, taking diagrams as the most fundamental tool. It recently got mentioned in Computer Weekly and Forbes, which is pretty awesome. It turns out to be a really useful way to think about quantum natural language processing, which is what lots of the folks at Cambridge Quantum are doing these days.
 QuiZX is a new, super quick library for ZXcalculus rewriting.
It is written in Rust, a systems programming language designed for writing fast, reliable software. Of course, that doesn't automatically mean its fast, but some experiments are looking pretty good! Here we build a diagram with 100,000 spiders and fuse them:
PyZX: Building a Zspider chain of size: 100000 Done in 219.52ms Fusing all spiders Done in 98.55s QuiZX: Building Zspider chain of size: 100000... Done in 12.99ms Fusing all spiders... Done in 17.47ms
...that's about 5000X faster. :)
 My student John van de Wetering got himself a PhD! Check out his thesis, which is actually two theses in one:
Abstract. This thesis consists of two parts. The first part is about how quantum theory can be recovered from first principles, while the second part is about the application of diagrammatic reasoning, specifically the ZXcalculus, to practical problems in quantum computing. The main results of the first part include a reconstruction of quantum theory from principles related to properties of sequential measurement and a reconstruction based on properties of pure maps and the mathematics of effectus theory. It also includes a detailed study of JBWalgebras, a type of infinitedimensional Jordan algebra motivated by von Neumann algebras. In the second part we find a new model for measurementbased quantum computing, study how measurement patterns in the oneway model can be simplified and find a new algorithm for extracting a unitary circuit from such patterns. We use these results to develop a circuit optimisation strategy that leads to a new normal form for Clifford circuits and reductions in the Tcount of Clifford+T circuits.
Congratulations Dr van de Wetering!
 Coen Borghans wrote a masters thesis giving efficient 2way translations between stabilizer ZXdiagrams and stabilizer subgroups. Here it is:
 PyZX, our library for manipulating quantum circuits with the ZXcalculus, is now installable via pip. As a consequence, it is now easy to "run" ZXdiagrams on a real quantum computer using the IBM Quantum Experience. Check it out:
Also, here are some download stats for PyZX. Join the party! >
 I'm now on Twitter, but not much of a Tweeter (yet). Follow me if you like: @AleksKissinger
 Louis Lemonnier completed a summer project with me last year, connecting the powerful pathsum technique for circuit verification to the ZHcalculus. Louis showed that the HH rule from pathsum is equivalent to a new rule called the Fourier hyperpivot, which has the twin benefits of being very useful for circuit simplification and sounding like a move from DragonBallZ.
UPDATE: There's now a paper about hyperpivoting. Check out the preprint:
 Hypergraph simplification: Linking the pathsum approach to the ZHcalculus. Louis Lemonnier, John van de Wetering, and AK.
 My student Sander Uijlen has passed his Phd defense! You can read his thesis here:
...or check out related journal papers on contextuality and causality.
 PyZX is an opensource Python library for compilation, optimisation, and simulation of quantum circuits using the ZX calculus. To get some idea of what it's about, check out this Youtube video:

Read a book!
Picturing Quantum Processes: A First Course in Quantum Theory and Diagrammatic Reasoning. Bob Coecke and Aleks Kissinger, Cambridge University Press
...which teaches quantum theory from the ground up, taking diagrams as the most fundamental tool. Order now from CUP, Amazon, or many other purveyors of fine printed goods. It has been the basis of a masterslevel Quantum Computing course running in Oxford for about 5 years and another course running in Nijmegen in 2018 and 2019. If you are interested in running a similar course, get in touch with me.
To get some flavour of the book, you can check out Categorical Quantum Mechanics, part 1 and part 2, which give approximately the first 8 chapters in a somewhat condensed package.
 I moved to Oxford! I'm happy to (re)join the Quantum Group in Oxford's Department of Computer Science in 2019.
 TikZiT 2 is now available for Windows, Linux, and macOS.
 Our causality paper is the topic of a recent blog post on the ncategory cafe. It also formed the basis of one of the four research threads at the 2018 Adjoint School of Applied Category Theory in Leiden.
 I wrote an ERCIM news article about some of the exciting new developments in graphical calculus for quantum computation, notably the new completeness results for Clifford+T and universal quantum computation.
 I coorganised a workshop with Pawel Sobocinski on string diagrams called STRING on Sept 89, satellite to FSCD in Oxford.
 We organised the 14th International Conference in Quantum Physics and Logic (QPL) at Radboud in 2017, colocated with a satellite workshop on quantum structures run by IQSA. With 109 registered attendees, 5 invited talks, 4 tutorials, and a total of 67 contributed talks across QPL and IQSA, it was a huge success!
 I was a keynote speaker at IQSA 2016, July 1016 in Leicester, UK.
 I gave a tutorial on process theories and graphical languages at QPL 2016, June 610 in Glasgow, UK.
 My student David Quick has passed his viva! His PhD thesis is called:
 Check out Quantomatic, a tool for (semi)automated reasoning with diagrammatic languages.
Selected Publications

Tensor Network Rewriting Strategies for Satisfiability and Counting
Niel de Beaudrap‚ Aleks Kissinger and Konstantinos Meichanetzidis
2020.
Details about Tensor Network Rewriting Strategies for Satisfiability and Counting  BibTeX data for Tensor Network Rewriting Strategies for Satisfiability and Counting  Link to Tensor Network Rewriting Strategies for Satisfiability and Counting

Universal MBQC with generalised parity−phase interactions and Pauli measurements
Aleks Kissinger and John van de Wetering
In Quantum. Vol. 3. Pages 134. 2019.
Details about Universal MBQC with generalised parity−phase interactions and Pauli measurements  BibTeX data for Universal MBQC with generalised parity−phase interactions and Pauli measurements

A categorical semantics for causal structure (extended version)
Aleks Kissinger and Sander Uijlen
In Logical Methods in Computer Science (LMCS). Vol. 15. No. 3. 2019.
Details about A categorical semantics for causal structure (extended version)  BibTeX data for A categorical semantics for causal structure (extended version)