Christopher K. Long

For many quasiprobability distributions, the set of positive (“classical”) states is difficult to characterize. However, for a random Kirkwood–Dirac distribution, we completely characterized not only the positive states, but also the positive measurements and unitaries.

We have just updated the arXiv with the accepted Physical Review A version so there is an open access peer-reviewed version: arxiv.org/abs/2405.17557

Since finishing my PhD viva on the 6th, with minor corrections, life has been busy. The discussion with Alex Thom and Simon Benjamin during my viva was insightful, and I'll have a better thesis as a result—thank you! My corrections are now done, but were slowed down by an accident on the 17th.

VQEs have 3 main problems: (i) excessive runtimes, (ii) susceptibility to noise, and (iii) optimizability. In our recent preprint (arxiv.org/abs/2606.17357), we address the first 2 without losing optimizability. We achieve this by designing pulses for 4-qubit gates that run up to 15 times faster.

Congratulations to Henrik Gothen and Yunming Qian for their first preprint and @djamilala.bsky.social for her first preprint on quantum information.

VQEs have 3 main problems: (i) excessive runtimes, (ii) susceptibility to noise, and (iii) optimizability. In our recent preprint (arxiv.org/abs/2606.17357), we address the first 2 without losing optimizability. We achieve this by designing pulses for 4-qubit gates that run up to 15 times faster.

For many quasiprobability distributions, the set of positive (“classical”) states is difficult to characterize. However, for a random Kirkwood–Dirac distribution, we completely characterized not only the positive states, but also the positive measurements and unitaries.

In our recent arXiv (arxiv.org/abs/2605.28936) we benchmarked QEC and magic state factories for spin qubits. By computing magic state production overheads as a function of initialization, gate, measurement, and decoherence times we estimated the runtimes for typical algorithms—see Fig.

On Friday, I submitted my PhD thesis! I'm looking forward to defending in August and sharing the thesis with the rest of you.

The University of Cambridge is hosting a Foundations of Quantum Technologies conference on September 15–18th to mark the 100-year anniversary of the discovery of modern quantum mechanics. Abstract submissions for talks and posters close May 4th. More details: www.girton.cam.ac.uk/events/found...

I finally read The Elements of Style by Strunk & White; I should have read it on day one of my PhD. At least I read it before writing my thesis. A free copy can be found on Kobo: www.kobo.com/ebook/the-el.... 1/3

I found Pullum's critical essay, 50 Years of Stupid Grammar Advice, helpful in discerning Strunk & White's rules from suggestions [1]. Pullum's essay is heavy-handed, and a counter-critique can be found in the following Stack Exchange answer: english.stackexchange.com/a/3223/695205 [2]. 2/3

I have finally finished mirroring my scientific @github.com repositories to @gitlab.com. Here is a tutorial by [justncodes](github.com/justncodes) which I modified: github.com/Christopher-...

Now is not a good time for citations: Miss-citing online-only journals and Google Scholar indexing non-existent articles cited by hallucinating LLMs. Maybe the silver lining is that this will undermine metrics such as citation counts and h-indices, forcing academics to be judged more holistically.

In case anyone else missed it: Python 3.14 released on the 7th of October: docs.python.org/3.14/whatsne...

I guess it's time I release a 3.14 pre-built version of PySTE: pypi.org/project/py-s...

With a long transfer from the Sahara to Fes, I finally finished going through the starter packs below. It was great to see everything you all have been working on! I like to spend some time reading through each profile, so I start to remember who's working on what. Please comment more starter packs!

With a long transfer from the Sahara to Fes, I finally finished going through the starter packs below. It was great to see everything you all have been working on! I like to spend some time reading through each profile, so I start to remember who's working on what. Please comment more starter packs!

Ever wanted to use virtual Z gates with arbitrary powers of SWAP? Introducing the virtual Z pulse: arxiv.org/abs/2509.13453. In our new article, we present a method for distorting a pulse sequence to implement single-qubit Z controls virtually.