Interactions: Conversation with Martijn van Calmthout

Post by Christine Horejs, Nature Reviews Materials.

The theoretical physicist Sam Goudsmit had a remarkable life. Not only did he discover the electron spin with his colleague George Uhlenbeck (for which they did not receive the Nobel prize – to the surprise of many colleagues), he was also the scientific leader of the Alsos mission, the United States mission searching for the ‘German nuclear bomb’. After the war, in 1958, he launched the pioneering weekly Physical Review Letters, which became one of the top publications in science.

Martijn van Calmthout, photo by Hilde Harshargen, De Volksrant

Martijn van Calmthout, former science editor of the Amsterdam-based newspaper De Volkskrant and now head of communication at the National Institute for Nuclear and High-Energy Physics (Nikhef), tells the thrilling story of Sam Goudsmit’s life in his book Sam Goudsmit and the hunt for Hitler’s atom bomb (first published in Dutch in 2016, now translated into English by Michiel Horn). From his days as a Physics student of Paul Ehrenfest in Leiden to the crazy times of the Alsos mission during the final days of World War II, Martijn van Calmthout describes a rather humorous theoretical physicist with a very tragic family history – he lost his parents in Auschwitz, despite trying to help them to immigrate to the US. Goudsmit worked with Zeeman, Bohr and Einstein, and was a good friend of Heisenberg, whom he eventually hunted down in Germany during his mission to catch the German nuclear physicists. However, Goudsmit always undermined his own achievements in quantum physics as well as his participation in one of the most exciting times in theoretical Physics: “My God, it is as if you dated Marlene Dietrich or something,” said Goudsmit when asked about his famous Physics friends in the 1920s. “Back then it was all so unimportant.”

We talked to Martijn van Calmthout about his new book and the stories behind it.

How did the idea for the book Sam Goudsmit and the hunt for Hitler’s atom bomb take shape?

In the upshot to the Einstein year 2005, I was doing research for a small book on Einstein, called Einstein’s Light. As Einstein was often in Leiden, I noticed the name of the Leiden student Sam Goudsmit, whom I did not know, but who turned out to be one of the discoverers of electron spin. I was intrigued and as I delved into his story, I also found the war time memoir Alsos, which he wrote. An important Dutch physicist with a real war adventure concerning nuclear developments in Hitler’s Germany. I was surprised that all this was hardly known in the Netherlands. I decided to write a biography. At that time, the archives at the American Physical Society (APS) were getting published online, so research became a lot easier. Continue reading

Behind the paper: A bridge between theory and experiment

On behalf of Marcus Huber

{credit}Christian Murzek 2018 murzek.com{/credit}

Supposedly, there are two very different species of physicists: theorists and experimentalists. This alleged division is the subject of numerous nerdy jokes, but is more seriously reflected in university curricula, academic positions, grants, papers and non-surprisingly, reviews. Our review is an attempt to bridge the apparent gap that often complicates communication, focussing on a specific area of quantum physics that has seen a close connection between theory and experiment.

The story behind this review starts well before it was conceived. After finishing my PhD in theoretical physics, I remember being approached by experimentalist colleagues, asking seemingly simple questions about quantifying high-dimensional entanglement. At first, I couldn’t comprehend their dissatisfaction with my writing down a self-adjoint operator—after all, this is what constitutes a ‘measurement’ according to the postulates of quantum mechanics. After being presented with a bunch of tangible tools that were screwed to an optical table and asked to explain how to realise that specific measurement, I realised how little I actually understood quantum experiments and how pointless all of my theorems seemed for answering the simplest of questions.

This initially painstaking interaction with the mysterious species of experimentalists eventually bore fruit and led to a series of collaborations with experimental groups. There was a recurrent theme in our interactions experienced also by many theorist colleagues—we were presented with final experimental data and asked to tell if it is possible to certify or even quantify entanglement. The answers would have always been easy had they done the experiment in a slightly different manner, but alas, what was done, was done. I then spent sleepless nights trying to understand what each particular setup meant and how one could construct theoretical tests of entanglement for each specific situation—a process that could have been much simpler had there been a comprehensive review bridging this divide.

At some point, one of my frequent experimental collaborators approached me with an interesting proposition: we could run experiments together. And indeed a short time later, Mehul Malik joined my group as a senior postdoc and we started exploring the intricacies of multipartite and high-dimensional entanglement of ‘twisted’ photons. The first ‘experimental’ papers with a majority of theory authors were born and slowly the entire group developed a common language. Two more senior postdocs of the group had reported very similar experiences in different experimental collaborations, with Giuseppe Vitagliano working on spin squeezing in cold atoms and Nicolai Friis analysing ion traps with 20 qubits. We had often talked and decided the field really needs a review that covers all aspects in a unifying language, but never found the time to actually materialise it.

When I was invited to write a review for Nature Reviews Physics, we knew this was the chance to finally realise that dictionary that should become a handbook for both theorists and experimentalists to talk to each other, while comprehensively showcasing the state-of-the-art of quantum technologies. Of course, our initial dream was a bit too ambitious, given that there are dozens of experimental platforms, each with their own techniques and whole books could be written just about the theory of entanglement. So while trying to remain as objective and comprehensive as possible, we naturally decided to focus on aspects that we found most exciting at the moment.

The time we were planning to write the review also coincided with the move of Mehul Malik to his new professorship in Edinburgh and overlapped with the parental leaves of both Nicolai Friis and Giuseppe Vitagliano. While all joyous occasions, it was hard to gather the crowd even in the same Skype conversation. Collectively editing, planning and writing a comprehensive review with strict length constraints seemed an insurmountable task under these circumstances. So we turned to collaborative online LaTeX editors and at different hours of day and night wrote and commented the present review. When Nature Reviews Physics approached us about whether we would be willing to try Overleaf for collaborating with the editorial team, we were already well acquainted with the workflow, and went through several rounds of excellent editorial feedback, without ever having to worry about version control or sending a single document via email.

Interactions: Anastasiia Novikova

Anastasiia Novikova will join Nature Reviews Physics in January after a PhD at Synchrotron SOLEIL and a postdoc at CEA Saclay in France.

What made you want to be a physicist? 

I was always curious to understand natural phenomena, and physics seemed to explain how almost everything worked in the Universe. Besides, I enjoyed the scientific approach used in physics: experiment and demonstration.

If you weren’t a physicist, what would you like to be (and why)?

If not a physicist, I would definitely be an artist. As a child, I was passionate about drawing and painting (and I still am). Shapes and colours of nature were always hypnotizing me.

Which historical figure would you most like to have dinner with — and why?

I have a whole list of historical figures but the one I would really like to meet is Richard Feynman. To me, he is a person remarkable for his manner of popularizing physics and capturing the audience. The first thing I would ask him: “What is your secret? “

Which is the development that you would really like to see in the next 10 years?

I would like to see the development of Artificial Intelligence in the domain of Genetics to help us understand such issues as genetic disorders.

What’s your favourite particle?

While studying the Physical Chemistry module at Pierre and Marie Curie University, I was fascinated with how the electronic structure of a compound could influence its colour. In this regard, my favourite particle is, definitely, the electron.

What would your dream conference be like?

The conference I dream of would be dedicated to the greatest discoveries of all time. And being imaginary, it would be organized by the pioneers, with, for example, Isaac Newton giving a Welcome speech.

Interactions: Zoe Budrikis

Zoe Budrikis joined Nature Reviews Physics after postdoctoral research at the ISI Foundation in Turin and at the Center for Complexity and Biosystems at the University of Milan and a PhD from the University of Western Australia.

What made you want to be a physicist?
In high school, I didn’t plan to study physics. I wanted to take Ancient History instead. But the timetable didn’t work out so I took physics classes and enjoyed them, and then I took some physics courses at university and enjoyed them so much I changed my degree. The rest, as they say, is history.

If you weren’t a physicist, what would you like to be (and why)?
It’s a cliché, but my backup plan/daydream is to open a bakery. I love seeing people enjoy food I’ve made, which is easy to do with cake! Plus, thinking about how to put unusual flavours and ingredients together is the kind of problem-solving I find relaxing. Of course, there’s a lot of physics involved in understanding how food works.

Which is the development that you would really like to see in the next 10 years?
Interdisciplinary science has really come to the fore in recent years, and I’m excited to see where that will take us. Especially because so many of the big problems in science and society – climate change springs to mind – require people with different backgrounds to work together to find a solution.

Which historical figure would you most like to have dinner with — and why?
I’d love to meet some of the everyday people of the past. Any era, really. Most of what I know about history is about big political figures, or famous authors/artists/inventors, and I think it would be fun to sit down with someone not at all famous and find out what their life was actually like.

What Sci-Fi technology would you most like to have (and why)?
I’d like everyone to have the Babel Fish from Hitchhiker’s Guide to the Galaxy.

What is your non-scientifically accurate guilty pleasure (could be film/series/book)?
I watched a lot of classic Dr Who as a teenager, and I retain a soft spot for alien planets that look remarkably like quarries.

Interactions: Giulia Pacchioni

Giulia Pacchioni played a big part in the launch of Nature Reviews Physics, but will return to Nature Reviews Materials next month. Still, she will always be part of the team.

What made you want to be a physicist? 
Feynman’s autobiography, Surely You’re Joking, Mr. Feynman! I read it as a teenager and it kicked off a long-lasting fascination for physics. For a while I also thought about becoming a mathematician, but then I was drawn by the richness of physics, a subject that stretches from the understanding of the origin of the universe to the conception of next-generation electronic devices. As many others I entered university thinking I wanted to be an astrophysicist, but after finding out more about the marvels of solid-state systems I ended up being a condensed matter physicist instead.

If you weren’t a physicist, what would you like to be (and why)?

I considered studying classics — I was particularly fascinated by the evolution of the Greek ancient language, as it gives insight on how languages developed. However, my secret plan has always been to open my own factory of soft toys. I would make fluffy versions of all the cutest animals, from the domestic to the rare. But I haven’t totally discarded the idea of owning a chocolate factory either.

Which historical figure would you most like to have dinner with — and why?

Dinner with Aristotle would be cool. He was such a great thinker I suspect there would be no shortage of topics to discuss, starting from his deep questions about the physical world. Maybe he could bring along his pupil Alexander the Great. He must have had a magnetic personality.

What would be your (physics) superpower?

Teleportation! I could pop in for lunch with friends in Paris, and chill on a beach in Sardinia in the afternoon. Coffee and cake on the Amalfi coast.

What’s your favourite (quasi-)particle?

Definitely skyrmions. They look so awesome with their arrangement of colourful spins. There is a lot of fascinating materials research going on to obtain smaller and more controllable skyrmions, and they have cool potential applications. Lately I’m getting into Majorana quasiparticles as well, as their observation requires top-notch condensed matter physics experiments and they might enable error-protected quantum computers. In preparation for when I will have my toy shop, I made a soft Majorana fermion that keeps me company in the office.

What Sci-Fi gadget / technology would you most like to have / see come true (and why)?

In Italy there is a comic-book character,  Eta Beta, who wears a little black skirt in which he can stock anything, a bit like in Mary Poppins’ bag, as objects become incredibly small (and hopefully light!) as they are stored in the pockets. I find such a garment would be practical, provided the storage is organized enough to find stuff speedily.

Interactions: Iulia Georgescu

Iulia Georgescu is the Chief Editor of Nature Reviews Physics. Previously, she was an editor of Nature Physics, where she managed to sneak in three original “Alice in wonderland” illustrations (1, 2, 3) and the self-declared best cover-line ever.

What made you want to be a physicist? 

Star Trek. More precisely Mr Spock and Mr Data. Do I need to say more?

If you weren’t a physicist, what would you like to be (and why)?

A SF/fantasy writer or a manga artist because I love daydreaming about fantastic adventures. I hope it’s not too late, and my best-selling work is yet to be published (well, written first).

Which is the development that you would really like to see in the next 10 years?

Detection of dark matter or anything else beyond the standard model.

What would be your (physics) superpower?

Flying would be pretty cool. What is nice about this superpower is that you can imagine various ways in which flight would work with its strength and limitations.

What Sci-Fi technology would you most like to have (and why)?

Teleportation would come in very handy, in particular to save my commute time.

What is your non-scientifically accurate guilty pleasure (could be film/series/book)?

As you might have guessed by now SF/fantasy books and manga/anime, although I do not feel guilty in the least.

Interactions: Andrea Taroni

Andrea Taroni is the Chief Editor of Nature Physics.

What made you want to be a physicist? 

Being the enlightened souls that they were, my parents told me I could study anything I wanted, provided it was a science. So I chose chemistry, because it was somehow in the middle between biology (which I tended to like) and physics (which I tended to find quite boring, at least at school) – but long term I had no intention of staying in science. Anyway, as things went on I realised that I hadn’t quite appreciated that a) chemistry is only in the middle if you imagine the spectrum between the sciences to be on a logarithmic scale (that is, physics explains A LOT more than I had initially thought); b) physics research is a lot more interesting than physics lessons; and c) I wasn’t very good at chemistry to begin with. I was lucky to work with a chap called Steve Bramwell in my last year of university: thanks to the project I worked on with him, I realised I liked magnetism. And in order to study that, I had to get a better grasp of fundamental ideas rooted in statistical physics and, ultimately, symmetry. This struck is very deep and very beautiful and it had the effect of helping me to start thinking like a physicist.

If you weren’t a physicist, what would you like to be (and why)?

I’m now beyond the age where it is even possible for me to cling on to my dream of being a footballer, but that was, alas, my burning ambition when I was growing up. I enjoy what I am doing right now a lot, but compared to football it is a very distant plan B. Had a pro football career come off, I would be now be looking at investing my money in property on the Mediterranean coast…and I can’t say I would be too disappointed with that. But you ask what I would like to be, and “property developer” is not something I ever aspired to be. The people I admire the most these days are, for want of a better description, practitioners: people that have dedicated themselves with passion and discipline to a particular art or craft. You can just tell when you meet such people – they might be famous artists or simply very good teachers that don’t get as much recognition as they deserve – but measured over time their influence over the people around them is huge.

Which historical figure would you most like to have dinner with — and why?

I answered this question the last time I did this kind of Q&A, and I said Julius Cesar and Cleopatra. I’m going to stick with that.

What would be your (physics) superpower?

Without doubt it would be the power of flight. Am I aiming to low? Because that still strikes me as a cool thing to be able to do.

What’s your favourite (quasi-)particle?

Probably the magnon, as I worked with it while I was doing research. It’s a nice, simple quasi-particle with a distinguished history in the physics literature. And once you understand how they work, you understand how a lot of other quasiparticles work too.

Which physicist would you like to see interviewed on Interactions — and why?

If you could go back in time, I would suggest Ludwig Boltzmann. As you can’t, I’m going to say Philip Anderson.