Michael Berry on the next century of quantum mechanics

Prof. Michael Berry talked about his work and the future of quantum mechanics in an interview during his recent visit to ICTS-TIFR for the ‘A Hundred Years of Quantum Mechanics’ program. Some excerpts:

Q: What is the status of the foundational questions in quantum mechanics now?

A: I have no idea, I don’t work on them. [...] Transport the question back to classical mechanics. Two points. Is Newton’s equation more fundamental than Hamiltonian’s? Philosophers could argue about it. In fact, Newton’s equations are more general, that’s another matter. 

This refers to work by Berry and others on curl forces: position-dependent forces that cannot be written as the gradient of a potential. Curl forces have many peculiar properties - symmetries do not imply conservation laws, the dynamics are non-conservative yet non-dissipative, and in many cases they cannot be generated by a Hamiltonian. I first heard about this fascinating topic when Berry gave a colloquium at NTU in 2016. There has been quite a bit of work on this topic since then, including a recent generalization to quantum curl force dynamics.

Q: Do you have any advice for people who work in this field or who aspire to work in this field?

A: Yes. I have two contradictory pieces of advice for people who ask me for career advice.

The first piece of advice is: don’t take advice.

But, if pressed, I would say that if I were starting out, I would probably work on quantum information. Probably, though I can’t tell — this is what philosophers call counterfactual history. So I would say: work on quantum information. There are so many riches to be uncovered there to do with these big Hilbert spaces, even with a modest number of particles. So that’s what I would say.

For context, Berry's main contributions to physics relate to the "simple" case of linear wave equations and single particle quantum mechanics - well-established theories that nevertheless held numerous surprises and emergent behaviour in their singular limits and asymptotic phenomena. We've only scratched the surface when it comes to exploring these effects in complex many-body quantum systems.

The full text of the interview can be found here.

 

 

 

Tenure review and impact: Named equations

To get tenure your work needs to have a clear impact. Impact can't be captured by simple rules such as publish at least x papers in a high impact journal. Standards differ too much between different research disciplines, so impact must be judged on a case by case basis.

Stronger cases for impact can be made more concisely. If you have a widely used equation named after you then likely you will "automatically" get tenure - no need to prepare a lengthy tenure dossier, since it is a clear cut case of lasting impact. 

While getting an equation named after you might seem like a daunting task, there are actually many examples of named new equations, models, or algorithms that have been adopted relatively recently. These examples give hints as to how you should strategise your own research directions if you want to use this method to secure tenure!

To start, the Lugiato-Lefever equation used to model Kerr frequency combs was first formulated in 1987. The first reference to it by others as the Lugiato-Lefever equation I can find is in 1997, after the original paper had already accumulated about 150 citations - a relatively long time.

Quantum algorithms are often named after their creators: Shor's algorithm, Grover search, and HHL immediately come to mind. But others are not: the quantum approximate optimization algorithm, quantum phase estimation, and quantum signal processing, to name a few.

The field of topological insulators provides numerous examples:

• Immediately after Haldane's key 1988 paper was published, others referred to it as "a model introduced by Haldane" and "Haldane's model". This continued for a long time, even including the seminal quantum spin Hall effect paper. The first reference to it as "the Haldane model" was the 2005 PRL paper "Orbital Magnetization in Periodic Insulators". A few papers followed this phrasing in the next two years, with it becoming widely adopted from 2008.
  
• The Kane-Mele model that started the field of topological insulators was named that way by others within a year and this name quickly stuck. 
• More recently, the first model of a quadrupole topological phase proposed by Benalcazar, Bernevig, and Hughes in 2017 started being called the Benalcazar-Bernevig-Hughes model in 2019. 
• In topological photonics we have the "Wu-Hu model" proposed in 2015, which effectively opened up the study of topological phases using all-dielectric photonic crystals. For many years this model lacked a catchy name, with many papers referring to shrunken/expanded photonic crystal designs. Then in 2023 something changed - 6 papers, all by different authors, started calling it the Wu-Hu model and now this name is being widely used!
  

Why do some equations or models get named after their creators and others don't? What makes a named equation special?

The examples taken from topological insulators relate to widely-used prototypical models. The models might lack rigorous justification from first principles or experimental feasibility, but they embody some phenomenon of interest and are simple enough to understand, boiling a mysterious effect down to its key ingredients - the heart of physics.

Names are used to allow specialists to communicate some complicated concept more concisely. Thus, naming after authors is less popular when a simple and sufficiently descriptive name exists. For example, "Berry phase" and "geometric phase" are both widely used. Similarly, if there are too many authors it becomes too cumbersome to refer to the model by their names. TKNN formula (from 4 authors' surnames) is widely used, but examples with more than four authors seem rare.

Finally, while it can help if a leading authority in the field starts using the name first, in all of the above examples the impact came before the name. But once the name is coined it becomes a lot more compelling for authors to work with your model, amplifying its impact.

Lead Editor opening at Physical Review Research

The American Physical Society is conducting an international search for a new Lead Editor of Physical Review Research, a fully open access, peer-reviewed journal welcoming the full spectrum of research topics of interest to the physics and physics-adjacent communities.

The Lead Editor is the primary scientific advisor to the journal and chairs the Editorial Board. They provide community oversight of the journal’s content and direction, strategically advising the journal’s Chief Editor in a consultative capacity. The role is key in helping shape the journal’s long-term goals and growing and elevating the journal within the community.

The ideal candidate will possess the following qualifications:

• Stature in one or more areas of research within the scope of Physical Review Research and within its author and referee community
• Visionary and strategic with the ability to look at what’s required in broad terms and contribute to the development of strategic plans
• Excellent stakeholder management and interpersonal skills, with a proven track record of making the right connections and build networks both internally and externally
• Impeccable communication skills and ability to engage others
• Ability to make prompt independent evaluations and decisions
• Track record of mobilizing a group of people (without direct line management authority) to effectively support the the goals of the journal and the portfolio at large
• Able to manage multiple priorities
• Experience chairing meetings with diplomacy and ensuring that all members have the opportunity to contribute to the Board meaningfully
• Proven track record of identifying opportunities for improvement and planning/executing delivery plans to implement those improvements
• Excellent knowledge of the scientific research landscape in the areas of coverage
• Enthusiasm for learning about new research areas and trends in scientific publishing
• Strong sense of integrity and a commitment to a diverse and inclusive research community

The Lead Editor is expected to maintain their present position and location while devoting a percentage of their time to this position (typically not more than 10%). The initial appointment is for a three-year term, with renewal possible after review. The position comes with a competitive stipend, which is negotiable and dependent on the established time commitment.

The search is open to all candidates regardless of their place of residence. Review of applications will begin immediately and continue until a candidate is selected. Applicants are invited to submit a CV and a cover letter describing their vision for the future of Physical Review Research to enhance the quality and impact of the journal. Nominations should include a cover letter describing why the nominee will make an effective Lead Editor. Inquiries, nominations, and applications should be sent to: PRR Search Committee, at edsearch@aps.org.

2024 in review

It was a busy year for me, hence the substantially lower posting frequency.

I became a dad in February. It really puts the insignificance of the academic rat race in perspective. I had a lot less sleep and less uninterrupted time for deep work, but thankfully as of mid-December we are finally able to sleep more than 4 hours uninterrupted.

After a tough 9 years as a postdoc I started at tenure track position at SUTD in July. I have had a bit of a breather before research students join next year. I'm looking forward towards starting some research with a more longer term horizon than "get something publishable out within a year" as is typical for postdoc positions. And teaching undergraduates for the first time has also been highly rewarding even if it does take up a lot of time.

Before joining SUTD I was encouraged to apply for a start-up grant. Proposal writing really was a struggle with a newborn. My proposal was extremely rushed and unpolished - my aim was to just get out something that met the requirements. And thankfully it was funded. Take-home message: your grant proposal doesn't need to be perfect, sometimes the topic and the timing are more important than getting everything just right. The only certainty we have is that a proposal that is not submitted will never be funded.

On the research side, I was a collaborator on 8 papers submitted or published, with a few more promising ideas in the pipeline. I also managed to give 8 conference/seminar presentations, including at a graduate school in Indonesia. While I didn't participate in any big international conferences or workshops, I did enjoy attending a few meetings in Singapore.

On the editorial side, I've already finished 3 years of work with Physical Review A and will continue for another term. Since June I have also been serving temporarily as an editor for Physical Review Letters, handling more than 100 submissions. While there is a lot wrong with academic publishing today, one shouldn't lump journals of academic societies such as the American Physical Society with profit-driven publishers.

Happy 2025 to all readers! And if there's anything you'd like to see more of next year, let me know in the comments or drop me an email.

Teaching at SUTD

This term (just finished last week) was my first time teaching undergraduate students. I taught the first year maths course, covering calculus and numerical modelling. Overall it was a good experience and not as hard as I was expecting, thanks in part to all of the course materials being ready-made by some of the other instructors.

SUTD has quite a special system for its undergraduate coursework. For the first term all students take the same introductory courses, including maths. Rather than teaching this as a single big lecture class, the students are split into 11 cohorts of about 45 students each, with two faculty members assigned to teach each cohort, plus additional teaching assistants. 

During a class, one faculty member would focus on delivering the content while the other would go around the room to answer any questions one-on-one. To further promote discussion and interactions amongst the students and teachers, the "lectures" are regularly broken up by example problems for the students to work through in groups. This means the classes are also longer than usual - 2.5 hours each, twice a week.

One thing we tried differently this year was to make the weekly problem sets optional. Students were encouraged to work through the assignments themselves, but they were not graded. The motivation for this was that with the advent of tools like ChatGPT it is very easy for students to copy and paste the questions and immediately get full worked solutions, so we didn't think this would be a reliable way to grade the students' progress.

The flip side to this, of course, is that if the assignments are not graded it is extremely difficult to motivate the students to complete them. Indeed, the only time I had students come for office hours was just before their mid-term exam when they were trying to cram all the content from the first half of the course. Many students were unprepared for the mid-term, but grades improved somewhat in the final.

From the point of view of a fresh lecturer, I found being paired up with more experienced lecturers very helpful. Each week I would teach one class per cohort, and spend the other class answering any student questions. This allows one to see what methods work better and what concepts students are struggling with in real time, helping to improve one's own style of teaching. 

Looking forward to teaching this course again and hopefully doing a bit better next year!

 

Topological Photonics 2025 workshop in San Sebastian: call for abstracts

The Topological Photonics 2025 workshop, to be held at Palacio Miramar in San Sebastian, on 30th June-2nd July 2025. This meeting follows similar workshops held in 2021, 2022 and 2023 and is aimed at gathering a critical mass of people working in the vibrant area of Topological Photonics as well as topology in other wave and quantum phenomena. Abstract submission is now open for contributed talks and posters. 

 The following confirmed keynote and invited speakers are confirmed:

Keynote speakers:

• Andrea Alù (The City College of New York – USA)
• Olga Smirnova (Technical University Berlin, Germany)
• Päivi Törmä (Aalto University, Finland)
  
• Shanhui Fan (Stanford University, CA, USA)
  

Invited speakers

• Alexander Cerjan (Sandia National Laboratory, US)
• Baile Zhang (NTU, Singapore)
• Chiara Devescovi (ETH, Switzerland)
• Clivia Sotomayor-Torres (ICN2, Spain)
• Dario Bercioux (DIPC, Spain)
• Ewold Verhagen (AMOLF, Netherlands)
• Frank Scheffold (University of Fribourg, Switzerland)
• Oded Zilberberg (University of Konstanz, Germany)
• Sylvain Ravets (C2N, France)
• Thomas Christensen (Technical University of Denmark, Denmark)

Please submit your abstracts here before 14th of March 2025. Registration deadline is 30th May 2025. Participants are advised to book rooms as early as possible, hotels fill up quickly at that time of the year. You can find more information at the meeting website.

The 17th Annual Meeting Photonic Devices, Zuse Institute Berlin, Germany

Call for abstracts for the 17th Annual Meeting Photonic Devices (AMPD2025), taking place at Zuse Institute Berlin, Germany.

Topics include nanophotonic devices and related simulation methods. The organisers aim for open discussions between experiment, theory, and numerical methods.

Invited talks will be given by:

Anna Tasolamprou, National and Kapodistrian University of Athens
Bumki Min, Korea Advanced Institute of Science and Technology (KAIST), Daejeon
Costantino De Angelis, University of Brescia
Costanza Toninelli, European Laboratory for Non-Linear Spectroscopy in Florence
Haejun Chung, Hanyang University, Seoul
Humeyra Caglayan, Tampere University
Jesper Mork, Technical University of Denmark, Lyngby
Kurt Busch, Humboldt University of Berlin
Mohsen Rahmadi, Nottingham Trent University
Nahid Talebi, Kiel University
Olivier Martin, EPFL, Lausanne
Thomas Pertsch, Friedrich Schiller University Jena
Tim Schröder, Humboldt University of Berlin
Further invited speakers to be confirmed.

Please consider joining this workshop as either a speaker (poster or talk) or as an audience member. The workshop is free of registration fees.

Important dates:

Abstract submission deadline: January 31, 2025
Decision about acceptance: February 15, 2025
Registration deadline: March 25, 2025
Workshop: April 02-04, 2025 

Further information is available at https://www.zib.de/workshop-photonic-devices/ampd2025.html