Interactions: Federico Levi

Federico Levi is a Senior Editor at Nature Physics.

What made you want to be a physicist? 

I was a rather curious kid — the annoying kind that asks a lot of ‘why’ questions. But I never found my interests to be limited to the natural world. The adolescent me somehow decided that good learning opportunities would come from a degree in physics or history or English literature. While I like to think that some natural inclination towards analytical thinking nudged me in the direction of physics, the reality is that my parents were pretty persuasive in their case against a career in the humanities. But once I started learning physics for real, I was hooked. When I got to quantum mechanics, I was totally sold.

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

I would like to write novels, I think. Too bad I’m not very good at it.

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

Thomas Kuhn, to thank him for having written a great book.

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

Understanding so much better the foundations of quantum mechanics, cosmology or the interplay between quantum physics and general relativity to realize that what we all assumed was clearly right is actually rather wrong.

What would be your (physics) superpower?

Skipping stones for hundreds of meters.

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

A time machine to undo stupid mistakes. Could probably have other uses too.

Interactions: David Abergel

David Abergel is an Associate Editor at Nature PhysicsBefore joining Nature Physics in 2017, David carried out theoretical research on graphene and other two-dimensional crystals, and quantum topological materials. 

What made you want to be a physicist? 

When I was a kid, I was really into astronomy, so I guess I’ve always had an inclination towards science. Then, as a teenager, I read John Gribbin’s In Search of Schödinger’s Cat. I loved it. The vivid picture he painted of how quantum mechanics works, how it’s so different from the classical world that we experience, and most importantly how we can use maths to understand it had me hooked. From that point on I never wanted to be anything else.

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

I would probably have ended up as a forensic scientist working for the police. I’m sure it’s nowhere near as cool as it looks on TV, but the idea of trying to piece together a lot of small clues to provide evidence for case seems like a really interesting type of problem solving.

What would be your (physics) superpower?

Getting code to compile first time!

What’s your favourite (quasi-)particle?

Undoubtedly the Cooper pair. I find it counterintuitive that the jiggling of an atomic lattice can make two negatively-charged electrons ‘stick’ together. And the fact that there is most likely a completely different mechanism that we don’t understand going on in high-Tc superconductors is a fascinating mystery.

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

Apart from the obvious ones like time travel and teleportation, I want someone to come up with a material that is soundproof, but allows cool air through. It would be the perfect window covering for warm summer nights.

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

Is this like one of those facebook things where you have to nominate five of your friends to keep the game going??!! But more seriously, seeing as he kind-of came up with the idea, I want to hear what Lev Landau’s favourite quasiparticle is.

Interactions: Elena Belsole

Elena Belsole is the Chief Editor of Communications Physics. An astrophysicist by training, Elena was the executive editor of New Journal of Physics, before joining Nature Research.

What made you want to be a physicist? 

Since the age of 8 I wanted to be a medical doctor. I have always been a very inquisitive person and I would have pursued any direction that was giving me as many answers as possible on what the world is all about. But the truly determining factor was meeting my physics teacher in high school. He was so inspirational and made things look so fascinating; he even introduced the Schrödinger equation to the class. I could not leave it at that. I had to learn more.

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

An herbalist I think. I love how you can forage and use herbs for medicinal use and being able to find a remedy for any minor ailments.  I also considered theatre acting for a short time.

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

Since I started University I had Richard Feynman lecture notes on my bedside table and always found the simplicity of his explanations fascinating, but I would probably not want to go for dinner with him. If I have to choose one person to take out for dinner I would go for `the queen of carbon’, Millie Dresselhaus. She has guided and inspired so many people and she was a great physicist in an environment that was (and to some extent still is) quite adverse to women, while also having a family. I would like to know how she did it all.

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

I would like to see physical methods effectively used for controlling and stopping cancer and other diseases in a way that is not intrusive and not damaging for the patient.

What would be your (physics) superpower?

Definitely teleportation. I cannot even imagine how many places on Earth and beyond I could visit if that was true.

What’s your favourite particle?

The neutrino. It is such a versatile particle. Perhaps it is because of my fascination with cosmic rays from astrophysical objects, perhaps because it can be used to probe the Standard Model, or maybe just because thousands of them cross our body every second and are impossible to see and difficult to detect. Regardless, they are fascinating and may be a key to solve the mysteries of the Universe.



Interactions: Vittoria Colizza

Vittoria Colizza is Research Director of the EPIcx lab at INSERM and Sorbonne Université.

What did you train in? What are you working on now?

My formal training is in theoretical physics, but already during my PhD my work was at the interface with biology. Since then, I’ve been working on the characterization, modelling and surveillance of infectious disease epidemics, moving progressively from theoretical approaches to increasingly applied research informing public health. If I have to use a single tag to describe my research it would be ‘Computational and digital epidemiology’, integrating statistical physics, mathematical epidemiology, computer science, statistics, medicine, public health, complex systems approaches, network science, data science, surveillance, numerical thinking and geographic information systems.

My research focuses on real epidemic outbreaks to gather context epidemic awareness and provide risk assessment analyses for preparedness, mitigation, and control. Applications range from human epidemics (e.g. 2009 H1N1 pandemic influenza, MERS-CoV epidemic, Ebola virus disease epidemic, childhood infections, antimicrobial resistance spread in hospital settings) to animal epidemics (e.g. bovine brucellosis, bovine tuberculosis, foot-and-mouth disease, rabies).

In 2011 I joined the French National Institute of Health and Medical Research (INSERM), after several years spent in interdisciplinary departments/institutions (my only affiliation to a Physics Dept. was during my education at Sapienza University in Rome).

How do you introduce yourself (e.g. I am a physicist/biologist/…) ?

It depends on the audience.

In front of an epidemic/medicine/public health community I’d just state that I’m a modeler, as this is the key information they would need about my profile, e.g. to distinguish my expertise from the one of field epidemiologists, biostatisticians, public health professionals, MDs, and others. But a few exchanges about my approaches would often identify me as a ‘stranger’ and force me to reveal I’m a physicist by training. I tend not to state that upfront as it may induce an unneeded distance that is not beneficial for the interaction.

Talking to physicists, I would introduce myself as ‘originally a physicist’ to establish a common ground facilitating the communication, but I would specify that my work is fully framed in the context of infectious disease epidemics (and therefore, it’s not physics anymore – at least most of the times).

In all circumstances, I try to introduce myself in a way that could avoid misunderstandings, assumptions, cross-disciplinary suspicion, and would allow putting my audience more at ease to have a comfortable and fruitful dialogue.

What did you find most difficult when you first had contact with other disciplines?

Definitely a long list of painful aspects that all interdisciplinary scientists experience – lack of shared language/notation/methods/practices, huge investment of time, confusion, need for uninterrupted nurturing of the interdisciplinary dialogue, mutual suspicion. These aspects are more or less foreseeable before embarking in an interdisciplinary endeavor (though experiencing them directly is unforeseeably painful).

What caught me completely by surprise was realizing that the very same reason behind interdisciplinary research – mindset diversity bringing additional richness – was also its biggest obstacle. Mindsets are mainly rooted in the disciplines of training of each scientist, thus shaping their ability to frame and interpret concepts. While each offers a different perspective to a given problem, they all need to be reconciled and synthesized in something new to achieve the knowledge advancement that interdisciplinary research aims to produce. And reconciling different mindsets, under varying conditions of rigidity, may be extremely challenging.

And what did you find most helpful to familiarize yourself with new concepts and jargon?

For me there was no other shortcut than reading reading reading out-of-my-field papers and books, attending Schools to complete my training, and discussing infinite times and for infinite hours with experts from other fields. And clearly I learnt a lot through the collaborations, as I still do.

Tell us about your experience the first time you went to a conference outside the field you trained in.

It was a rollercoaster of highs and lows. On the low points there was definitely the intimidating feeling of being an outsider along with the depressing realization that the community didn’t feel any need for outsiders… Up to the moment I realized that my just-developed model was able to answer the questions left open by the keynote speaker – so after all, the community didn’t have all the solutions within the boundaries of its discipline. This was a very powerful impulse for a young post-doc starting interdisciplinary science.

What would be your advice to a PI leading an interdisciplinary group?

I don’t think there is a single recipe for success. But I learnt that there are many important skills –beyond scientific expertise –  that are crucial to a successful and effective interdisciplinary dialogue. Among them, respect for other disciplines, for other points of view, as well as tolerance for ambiguity. These are not taught in courses and should be fostered and practiced in the everyday lab life. The aim is for young researchers to learn how to establish comfortable, engaging and unassuming scientific interactions, lowering cross-disciplinary barriers and removing perceived hierarchies of discipline importance.

Is there any anecdote you would like to share?

Oh yes, I have so many! Are you coming to the Nature Reviews Physics event in London on Feb 26? 😉

Interactions: Athene Donald

Athene Donald is a professor of soft matter and biological physics at the Cavendish Laboratory, University of Cambridge.

What did you train in? What are you working on now?

I was educated in Cambridge in the so-called Natural Sciences Tripos, ultimately specialising in Theoretical Physics. That meant a broad course in the first year – physics, chemistry, materials science and maths – that narrowed down by the third year. I could easily have studied some biology in the first year, but as I had been so put off it at school by the fact it seemed to consist simply of memorising facts, it never crossed my mind to do so. So my formal biology education simply consists of two years at school, not even an O Level.

Although I specialised in Theoretical Physics I soon realised I did not want to spend my life only doing theory and went on to do an experimental PhD (‘Electron Microscopy of Grain Boundary Embrittled Systems’). Although electron microscopy – as well as other microscopies – has formed the core of my research, I have switched the kinds of materials I look at considerably during my career. After a first post-doc continuing on metals I switched to polymers and, over time, moved to biopolymers (first polysaccharides and much later proteins) and ultimately cellular biophysics.

How do you introduce yourself (e.g. I am a physicist/biologist/…) ?

A physicist working at the interface with biology. For my postdoctoral years, however, I was working, not in a physics department but in materials science and, in the USA for four years, that was within the Engineering Faculty.

What motivated you to move away from active research?

It was not a conscious decision! Back in the 1990s I was invited to serve on one of the very first government-organised so-called Foresight panels, looking at the future of the Food and Drink industry (at that time my biopolymer research largely related to food rather than biology per se). The broad range of people on that committee, and how they came together, fascinated me and I realised committee work was actually rather interesting. Over time I served on many different sorts of committees, internally within the university, with research councils and more and I found it taking up increasing amounts of time but also, on the whole, rewarding.

What really pushed my research over the edge was in 2010 when I took on two roles (neither to do with interdisciplinarity!): I became the University’s first Gender Equality Champion, which gave me the opportunity to work with the senior management to try to implement real policy changes and interventions to level the playing field for all across the university; and I became chair of the Royal Society’s Education Committee, dealing with 5-19 education at the time that Michael Gove as Secretary of State was introducing enormous changes to the curriculum. Neither role had any formal associated time commitment, but  they inevitably grew to fill (and more) the time available.  Both rewarding, both taught me a lot about different issues and ways of interacting with people from very different backgrounds. I continued in both those roles until 2014 when I became Master of Churchill College.

What did you find most difficult when you first had contact with other disciplines?

As I indicated, I had essentially no formal biology training and the world of genetics – and the language – had anyhow changed radically since my education. So the initial problem I faced was in understanding the language. When I was first involved in a collaboration with a plant scientist in the area of starch I suspect we both spent about a year just understanding what the other was saying and what our disciplines could and could not offer each other. To my mind, what is absolutely crucial in this formative stage, is finding the other person congenial enough you want to spend the time working together through this potential barrier.

And what did you find most helpful to familiarize yourself with new concepts and jargon?

Time! There is no short cut to getting to grips with a subject unfamiliar to you. I think it is also important to realise that working at the interface with another discipline does not mean you need to know everything about the other discipline. Recognizing what you absolutely do need to know but also there is plenty that, at least at that point, is not necessary so you can home in on the essentials, is crucial. Otherwise it can just seem an insurmountable problem. Of course over time what is vital to know may expand, but by that point it may seem less formidable a challenge. I think having someone you feel comfortable asking naïve questions of is also important; this comes back to having a good relationship with your collaborators. If you don’t feel relaxed about asking something basic the collaboration is probably not going to flourish. Of course sometimes collaborations will be with multiple individuals, possibly multiple disciplines, and then the tactics may need some modification.

Tell us about your experience the first time you went to a conference outside the field you trained in.

A general sense of confusion is what I remember most clearly. The diagrams – of protein structures – seemed mysterious as their presentation was so different from how a physicist would have approached the problem – and that left me with a profound sense of being out of my depth. If the basics seem incomprehensible it is hard to extract much useful information, however willing one may be. Coming into a new field also means that you probably don’t know anyone else in the room and that sense of isolation can be quite intimidating. Once you have some results (even if only a poster) it provides an entrée, so that other people will come up and introduce themselves. But that first step into the unknown can be daunting.

What would be your advice to a PI leading an interdisciplinary group?

Remember everyone comes with different experiences, skills and jargon. Somehow your job is to keep that constantly in mind like an orchestra conductor, to make sure people respect each other’s skills and make the best use of these they can. It is important not to let someone who is an expert in one area make another student whose skills sit elsewhere feel stupid or group dynamics can go sadly awry.

Is there any anecdote you would like to share?

Moving away from the heart of a discipline can make colleagues very uncomfortable. Working with starch, not the typical sort of material a physicist in the 1990s would have thought ‘respectable’, meant I came in for a lot of flak from my seniors. Being told ‘things have come to a sad pass when people at the Cavendish study starch’ by one of these was depressing. Added to this is the fact that, as a woman, people’s biases probably gave them a lower opinion of me anyhow at the time. Hence I was accused at a conference of doing ‘just domestic science’ – and that after I’d given an invited paper. It was sometimes hard to feel positive in an atmosphere like that. Again, having people around you who you trust and can rely on is vital to provide the balance to any such hostile colleagues.

Interactions: Bart Hoogenboom

Bart Hoogenboom is a professor of biophysics at University College London.

What did you train in? What are you working on now?

My undergraduate degree was in physics, I did a final-year research project on the electronic properties of buckyballs (C60), and a PhD project on high-Tc superconductors, that is, all solid-state physics. During my PhD, I learnt how to build and use scanning tunnelling microscopes, which came handy when as a postdoc, I developed atomic force microscopy methods to image solid–liquid interfaces at atomic/molecular resolution. At present, my lab still makes extensive use of atomic force microscopy, complemented by other methods, largely to study — often by real-time, nanoscale visualisation — how biological molecules interact with each other and self-organize to collectively carry out tasks that are important for health and disease. Examples of such tasks are the repair of DNA damage (important in various cancer therapies, for instance), the perforation of cellular membranes (such as in bacterial attack and immune defence) and the regulation of transport into and out of the cell nucleus (exploited by viruses and in gene therapies, for example).

How do you introduce yourself (e.g. I am a physicist/biologist/…) ? 

By my training and way of thinking, I am very much a physicist. That said, I try to do interesting science, and in doing so am not too concerned about the question whether that science happens to be more physical or biological.

What motivated you to change your field of research?

For my PhD, I was working on intellectually challenging questions regarding local electronic excitations in superconductors, which was great fun. However, to keep me motivated and interested on the longer term, I felt that I would benefit from broadening my research horizons and learning about other fields of science. Biology has the advantage of such broadness, with a nigh-infinite collection of questions and problems and ample scope for physicists to make meaningful contributions.

What did you find most difficult when you first had contact with other disciplines? 

I find biologists on average more conservative than physicists. In my experience, physicists tend to be more open to new concepts and methods, even if their immediate use or validity in a practical context is unclear. By contrast, most biologists know that many concepts may apply in nature and many methods may a priori be helpful; however, the hard work is often not in defining a new concept or new method, but in determining which ones (out of many) are useful for the particular biological problem that they are working on.

And what did you find most helpful to familiarize yourself with new concepts and jargon?

To start with, I worked my way through a cell biology textbook. That took quite some patience, but in the end I could read relevant scientific literature and talk to biologists without feeling excessively ignorant. Next, in such discussions across disciplinary boundaries, it helps to be honest about gaps in one’s knowledge. I must have asked many, many naïve questions (and still do), and I count myself fortunate with many fantastic collaborators willing to answer such questions and even do research projects with me.

Tell us about your experience the first time you went to a conference outside the field you trained in.

I felt rather lost and was wondering what on earth I was doing there.

What would be your advice to a PI leading an interdisciplinary group?

A good interdisciplinary research team is a treasure chest that contains much more knowledge and skills than a PI can have on his/her own, and this can be further enhanced by collaborations with labs that have complementary expertise. For a PI leading such a group, my main advice is to appreciate and make best use of such knowledge and skills, encouraging the team to help each other and show a similar open, communicative and collaborative approach when interacting with other labs.

Is there any anecdote you would like to share?

Interdisciplinary communication can sometimes get a bit lost by lack of proper translation. Some years ago, I had done preliminary experiments to visualise the assembly of immune proteins that punch holes in target cell membranes. My postdoc at that time struggled to replicate my results in a room where the heating – not for the first time on our building – was failing. When he next reported to our biological collaborators how he had solved the problem, ‘I put the sample on a hot-plate’, our collaborators went through the roof. To alleviate their major concerns over what we had done to the delicate proteins, it sufficed to give them the appropriate biological translation of my postdoc’s remark, ‘He incubated the sample at 37oC.’

Interactions: Georgia Francis

Georgia Francis is a Senior Editorial Assistant for the Nature Reviews journals, who works hard to keep Nature Reviews Physics running smoothly.

What is your role? What do you do?

I’m a Senior Editorial Assistant — I act as a first port of call for authors and editors for the online submission system we use to handle all drafts of manuscripts. I am responsible for ad hoc duties, questions and queries, as well as managing  and tracking author and referees via the online database system. I am also responsible for checking and obtaining legal documentation, and ensuring that the flow of manuscripts is timely in relation to peer-review through to acceptance.

What do you enjoy about working on Nature Reviews Physics?

I thoroughly enjoy working with the authors and the editors of Nature Reviews Physics;  they make my job rewarding and fun!

What do you find challenging in interacting with physicists (authors, reviewers, editors)?

Part of my role is to ensure that manuscripts are on track for peer-review. Quite often the reviewers require extra time to complete their duties because they’re exceptionally busy! They’re always very polite in response to my emails however which makes the job a little easier.

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

The historical figure I would most like to have dinner with is definitely Charles Darwin – I’d just be eager to see what he was like in person and express amazement at his influential work on evolution and humanity in general!


Interactions: Myfanwy Evans

Myfanwy Evans is an Emmy Noether Research Group Leader at the Institute for Mathematics, Technische Universität Berlin. Her research is in the field of geometry and topology in soft matter physics.

What did you train in? What are you working on now?

My undergraduate degree was in science, majoring in mathematics. My PhD was already in an interdisciplinary setting, officially part of “Physical Sciences”. It involved mathematics, physics, with some chemistry and biology on the side. Ever since my research has been swinging between mathematics and physics, depending on my collaborators and students at the time. My current research is focused on a theoretical framework to understand tangling in soft matter systems. It uses geometry and topology to investigate how filaments can tangle in a variety of settings, in the view of making a connection with protein and polymer physics.

Do you think of yourself as a mathematician or physicist?

Both and neither! Much of the content of my research is geometry, but the style in which I do it is more physics. However, I like to define my research via the problem that I am trying to solve rather than a specific discipline and I don’t like to be restricted by the methodology or traditions of a specific discipline.

What motivated you to move to this field of research?

I had already started in this general area as a PhD student, and it really grabbed me as an interesting topic. I finished my PhD with far more questions than answers, and this has snowballed into an array of research topics that I am still working on today. My motivation to continue in this direction is driven by my own curiosity, and a kind of religious belief that the results I am getting are so beautiful that they must be important.

What are the main challenges and the main advantages of working in an interdisciplinary team?

The main advantages are that everyone can bring something unique to the table, and the breadth of expertise opens really interesting research directions. I find that the students feel less constrained by their prior knowledge and disciplinary expertise, and are able to work on broad problems from many perspectives, learning a huge amount along the way. The main challenge is keeping the research also relevant to specific fields, in particular for PhD students who wish to stick to a more traditional discipline. Finding the right place to publish, that means reaching the right readership, is always a key problem too.

Do you find it particularly difficult to obtain funding? Or to get your research published?

I think that interdisciplinary research has become a big focus of many funding agencies, and in general I don’t find any major obstacles in obtaining funding from the standard sources. I find the same with scientific publications, where new interdisciplinary findings are often published. Of course, there are exceptions and I have a handful of examples of journals claiming that the research is “not physics” or “not mathematics”, without refereeing the scientific content. But these are few and far between.


The rise of open source in quantum physics research

Post by Nathan Shammah and Shahnawaz Ahmed.

Open-source scientific computing is empowering research and reproducibility. It forms one of the principles of the ‘open science’ movement, which aims to promote the spread of scientific knowledge without barriers. Open-source software refers to code which can be read, modified and distributed by anyone and for any purpose under the various open-source compliant licenses. This ‘open source way’ could extend beyond just software and is impacting quantum physics research in radically different ways.

Quantum-tech open source

Quantum computing represents a different computational paradigm from conventional computing: it exploits quantum mechanics at the algorithmic level. As quantum algorithms need to be run on quantum devices, advances in hardware development, currently underway, are crucial. At the same time also software for quantum computing needs to be developed for various purposes – compilation, control, noise modeling, simulation and verification. Open source is driving the development of the quantum computing software ecosystem [Fingerhuth18].

To some extent, the very structure of research in quantum technology is being reshaped by open-source projects to a new degree, for example allowing theorists to run quantum physics experiments from the cloud, without ever entering the lab (to the relief of experimentalists) [Zeng17]. In most cases, the tools are open source in a bid to involve the community of researchers and software developers to come together to build the next generation of software for quantum computing.

Beyond quantum computing there is also a broader area of quantum physics research that is being driven by open source. Some projects aim to provide a broad set of tools which can be used for quantum physics research, such as QuTiP, a Python toolbox for open quantum system simulations, which was started as early as 2011 [Johannson12]. Recently tools such as QuantumOptics.jl (a Julia package for quantum optics simulations) or Google-backed Open Fermion (simulating fermionic interactions and other chemistry problems) have been released for tackling different types of research problems. Other projects are purpose-specific, such as Pennylane (focussing on machine learning and quantum physics), ProjectQ (translating quantum programs to “any back-end”), and NetKet (Neural Network Quantum states for solving quantum many body problems). A community-maintained list of software can be found here.

 Factors contributing to the rise of scientific research with open-source software

Scientific progress is fueled by collaborations and development of ideas from others. In the same spirit, open-source is built upon the contributions of the community and there are several factors that are leading to its adoption beyond quantum physics research.

Firstly, open-source libraries allow fast reproducibility of results. By preventing the reinventing of the wheel and the need to start projects from scratch, they allow for a rapid development, testing and prototyping of ideas and extending previous work. This accelerates the rate of discovery, as new results can be investigated by other researchers tinkering with existing code.

Secondly, there are a variety of tools that increase productivity and collaboration. There is a general trend in scientific research in working in larger teams [Fortunato18] and open-source tools are helping in that. Github or Gitlab are websites that coordinate delocalized teams to work on the same coding project (similarly to Dropbox for file syncing and Overleaf for typewriting). One can also work interactively on code with solutions such as the Jupyter Lab computational environment, Google Colaboratory or CoCalc.

Then, there are well established tools for open-source software development from start to finish:  Travis CI, Anaconda, and the community-managed ‘conda-forge’ channel, can all be set-up easily to take care of testing, continuous integration and software packaging and distribution.

Finally, there are tools specifically crafted to better adapt to the modern characteristics of research publication, in which papers in journals have a background of data or software. Zenodo for example allows the publication of open-source software together with published papers and instantly attributes to it a DOI reference, without waiting for the (sometime lengthy) peer-review process. The crystallization of software is also a guarantee for reviewers and other researchers who might want to use the same code.

Python and machine learning as success stories for open source

 The benefits of the open-source approach can be clearly seen in machine learning, especially deep neural networks. Suddenly, it has become very easy to tinker and use even the most advanced methods in machine learning thanks to the availability of code and tools to modify and run them. With Google’s TensorFlow or Facebook-backed PyTorch, the power of deep neural networks reached the masses, leading to very creative applications.

As a result, we are also witnessing the impact of machine learning to all areas of natural sciences and tasks, from designing quantum experiments [Melnikov18] to detecting gravitational waves [Gabbard18].

An important factor for the wide adoption and use of machine learning tools is Python. It is an interpreted programming language that has seen a steady growth in adoption, based on a wide environment of modular independent software packages (libraries) that can be used together for numerics (SciPy), generating visualizations (Matplotlib), sharing code (Jupyter notebooks) and much more.

For some applications, Python’s limited computational performance (generally lower than C, C++ or FORTRAN) can be overcome by writing parts of the code in other languages and calling them from Python or using targeted solutions such as Numba or Cython to compile parts of the code into fast machine code.

But what really sets it apart its intrinsic code-writing efficiency and speed of developing prototypes, as one can more easily debug software on the go. As pointed out by Guido Van Rossum, the creator of Python, in a recent video interview for the MIT AI lecture series, scientific research through numerical means is usually a trial-and error creative approach, where the very investigative process benefits from an interactive feedback loop. The faster the loop, the faster the distillation of code.

Can quantum physics and quantum computing follow in this path by going the open-source way, accelerating the discovery of physical phenomena? Below we provide an example drawn from our recent experience.

PIQS: an example of open source package for physics research

 A major drawback in the development of quantum technology is the emergence of stronger noise as the system size grows, a process generally referred to as decoherence. The quantum system is never completely isolated, like Schrödinger’s cat inside the box, but is ‘open’ to interactions with the environments. The theoretical description of such coherence-averse processes in many-body quantum physics dynamics is itself problematic. This is because the very computational space grows exponentially with the number of qubits N, faster than 2^N (actually a daunting 4^N even if major assumptions simplifying the possible correlations of the open system are made).

We have recently released an open-source library, the permutational invariant quantum solver (PIQS) [Shammah18], to simulate a broad range of effects with an exponential advantage over the straightforward simulation of the open quantum dynamics. With PIQS, it is possible to include local effects in the noisy dynamics and energy dissipation, as well as the incoherent influx of energy from an external source, such as that mediated by a pumped cavity field by intermediate Raman processes in clouds of atoms illuminated by laser light [Baumann10,Bohnet12].

PIQS is quite versatile and addresses a series of open questions in the thermodynamics of quantum systems. This library can describe a broad range non-equilibrium effects in large systems of qubits, or ensembles of two-level systems, such as Dicke superradiance, which is the cooperative emission of light from an ensemble of identical two-level systems, in presence of sub-optimal experimental conditions, such as in solid-state devices, in which inhomogeneous broadening and local dephasing spoil the simple textbook picture of coherent light-matter interaction [Shammah17].

Due to the universality of the mathematical language in which quantum mechanics speaks, this tool can also describe spins in solid state materials and more generally, qubits engineered on a broad variety of platforms, from lattices of atoms to defects in diamond [Bradac17,Angerer18,Rainò18]. The use of permutational invariance has been crucial for the exponential reduction of the system space. The PIQS library joins other numerical investigations and libraries leveraging on symmetries in Lie algebras in tensor spaces [Kirton17,Gegg17].

By integrating the PIQS library into QuTiP, the quantum optics software in Python first released in 2011, this purpose-specific tool is now accessible to a wide community of users already familiar with this other well-established open-source software. This agility is another example of the modularity not only of the Python ecosystem, but of modular libraries themselves.

QuTiP itself is the example of a flexible library, which is used by theorists to test ideas or explore new physics, but also by experimentalists, who might want to analyze data or obtain predictions for how to tune the knobs of their experiments, including those involving the first error-prone quantum computers.

The future of quantum open source

 Open-source libraries like PIQS and QuTiP and the community of developers-researchers seem a key drive to the development of quantum technologies, as they offer the opportunity for creative interactions and novel solutions, as well as the capability to tinker with open problems.

Training more theoretical physicists and experimentalists on how to code collaboratively and develop open-source tools is another important aspect to train the next generation of future quantum programmers. At the same time, making this process easy and efficient, so that it can complement fundamental research, is paramount.

Involving the wider open-source community to use the knowledge and skills of expert software developers can also help to develop better simulation techniques or tools, for example for running simulations on GPUs or clusters. The two communities can learn from each other: one can help to adopt the best software development techniques and the other can demystify quantum quirkiness to facilitate the search for new and creative applications.

Finally, we look forward toward the development of institutional avenues to open-source quantum computing. Currently, only private ventures offer researchers cloud access to quantum machines [Zeng17], due to the costs of hardware development and software engineering infrastructure. As the community and tools of open-source software develop, we can envision in the future of quantum computing — and broader quantum technology research — also a network of scientific and institutional laboratories providing cloud access to experiments. This would contribute to reshape and possibly accelerate the rate of discovery in basic quantum physics research.


[Fingerhuth18] Mark Fingerhuth, Tomáš Babej, and Peter Wittek, Open source software in quantum computing, PLoS ONE 13 (12): e0208561 (2018).

[Zeng17] Will Zeng, et al. “First quantum computers need smart software.” Nature News 549.7671 (2017): 149.

[Johansson12] J. R. Johansson, P. D. Nation, and F. Nori: “QuTiP 2: A Python framework for the dynamics of open quantum systems.”, Comp. Phys. Comm. 184, 1234 (2013); J. R. Johansson, P. D. Nation, and F. Nori: “QuTiP: An open-source Python framework for the dynamics of open quantum systems.”, Comp. Phys. Comm. 183, 1760–1772 (2012)

[Fortunato18] Fortunato, S., Bergstrom, C. T., Börner, K., Evans, J. A., Helbing, D., Milojević, S., … and Vespignani, A. Science of science. Science, 359, 6379, eaao0185 (2018).

[Melnikov18] Alexey A. Melnikov, Hendrik Poulsen Nautrup, Mario Krenn, Vedran Dunjko, Markus Tiersch, Anton Zeilinger, and Hans J. Briegel, Active learning machine learns to create new quantum experiments, PNAS 115 (6) 1221 (2018)

[Gabbard18] Hunter Gabbard, Michael Williams, Fergus Hayes, and Chris Messenger, Matching Matched Filtering with Deep Networks for Gravitational-Wave Astronomy. Phys. Rev. Lett. 120, 141103 (2018)

[Shammah18] Shammah, N., Ahmed, S., Lambert, N., De Liberato, S., and Nori, F, Open quantum systems with local and collective incoherent processes: Efficient numerical simulation using permutational invariance. Phys. Rev. A 98, 063815 (2018)

[Baumann10] Kristian Baumann, Christine Guerlin, Ferdinand Brennecke and Tilman Esslinger, The Dicke Quantum Phase Transition with a Superfluid Gas in an Optical Cavity. Nature 464, 1301 (2010)

[Bohnet12] Justin G. Bohnet, Zilong Chen, Joshua M. Weiner, Dominic Meiser, Murray J. Holland and James K. Thompson, A steady-state superradiant laser with less than one intracavity photonNature 484, 78 (2012)

[Shammah17] Nathan Shammah, Neill Lambert, Franco Nori and Simone De Liberato, Superradiance with local phase-breaking effects. Phys. Rev. A 96, 023863 (2017)

[Bradac17] Carlo Bradac et al, Room-temperature spontaneous superradiance from single diamond nanocrystals. Nat. Commun. 8 1205 (2017).

[Angerer18] Andreas Angerer et al. Superradiant emission from colour centres in diamond. Nature Physics 14, 1168–1172 (2018)

[Rainò18] Gabriele Rainò, Michael A. Becker, Maryna I. Bodnarchuk, Rainer F. Mahrt, Maksym V. Kovalenko and Thilo Stöferle, Superfluorescence from lead halide perovskite quantum dot superlattices. Nature 563, 671 (2018)

 [Kirton17] Peter Kirton, and Jonathan Keeling, Suppressing and restoring the Dicke superradiance transition by dephasing and decay. Physical review letters 118, 123602 (2017).

[Gegg17] Michael, Gegg, and Marten Richter, PsiQuaSP–A library for efficient computation of symmetric open quantum systems. Scientific Reports 7, 16304 (2017).


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. Read more

Behind the paper: A bridge between theory and experiment

On behalf of Marcus Huber

Christian Murzek 2018

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.

How I wrote a graphic biography of physics Nobel laureate Maria Goeppert-Mayer

Post by Cliò Agrapidis — read the graphic novel here.

Being a female PhD student in theoretical condensed matter physics, I am part of a growing number of women in STEM. Being part of this group has made me aware of several initiatives related to it: from groups forming to reunite women scientist and/or to inform the public about women in STEM (500 women scientists, Women in research), to specific funding programs for women (like the one from the L’Oreal Foundation). Major journals (including Nature) publish editorials and data on the current situation for women in science and I find myself reading and sharing them almost daily. Being part of this group makes me feel invested in talking about this and other academia-related issues, acknowledging them among my peers and my colleagues and whoever is patient enough to listen to me.

This is how I found myself at the Lucca Comics&Games, the largest comics fair in Europe, talking about mental health in academia to a cartoonist, while other cartoonists and publishers were at our same table. Having finished with that, a young member of the BeccoGiallo publishing house asked me about the women in science issue, if it is something in which I am interested. After my affirmative response and some more small talk, he explained to me that he and a younger collaborator were launching a new comics website, with the intention of publishing short graphic journalism stories about current events but also, more in general, as a platform for informing the public about broader modern issues. They asked me whether I would write biographies of women scientists, with the intention of ‘going beyond Marie Curie’. I accepted and so I started collaborating with STORMI, an Italian online magazine dedicated to graphic journalism.

The next step I took was to write down a list of important female scientists from the past that not everyone knows. The first confirmation that many of these women are not widely known came when I showed the list to my partner, who is also a physicist: he did not know more than half of the people on the list. I sent the list to the two editors of STORMI with a short subject for the biography of Maria Goeppert-Mayer and a first suggestion for the order in which I would work on the list. As I expected, they did not know the names of the dozen scientists I had written down, but this is the core of the project: showing people how women have been part of science, not in big numbers as men (mostly because of regulations that did not allow women to do science), and how we, the public, have forgotten them: it is time we remember.

Comic as a medium has the advantage of using pictures. You can say a lot without too many words. For example, in Maria Goeppert-Mayer’s biography, one of my favourite illustrations is the one depicting Maria’s movements around the U.S.A. Sure, one can make a list, but it will not immediately show the distances she actually covered.

Another idea, which came from the illustrator I collaborated with, the talented Eliana Albertini, is to use different colors for different life periods. Again, one can divide the text in paragraphs, or chapters, but it does not have the same visual effect.

There was another problem that was very clear to me: the website is in Italian, but the language of science is English. So, I translated my own text into English and even asked my partner to make a German translation. That way, the comic is now available as pdf in three languages, and can reach a much broader audience.

I started with writing about a woman physicist because physics is my field and because when we ask people to name any female scientist they will most probably say Marie Curie and stop there. But there was another woman who got the Nobel Prize in Physics, and now we finally have a third one (which made our comic obsolete, but made us very happy). I will not restrain myself to physics: I have already written the text for Emmy Noether’s biography, my never-tired editor Mattia Ferri has contacted an illustrator, and we hope this story will be available soon. But there are other scientific fields to cover: biology and informatics, for example. I am now focusing on prominent female scientists of the past, but my hope is to be able to write stories about living scientists, maybe a graphic interview, in order to show to the public, but also to some fellow scientists, that science is not a men’s affair: women have been there, they are there, and they will be.

What is physics? Challenges and opportunities when working at the interface with other disciplines.

Post by Stefanie Reichert, Nature Physics

This year’s Berlin Science Week kicked off with a diverse programme. Among many events, visitors could discuss the connection between art and astronomy or learn how new technologies can be inspired by nature, or participate in a panel discussion at the Springer Nature office. The panellists set out to find an answer on how we define physics today, and to map out the boundaries with other related areas such as chemistry or biology.

Meet the panellists in our interviews from the run-up to the event: Abigail Klopper, Alba Diz-MuñozCosima Schuster, Magdalena Skipper Beatriz Roldán Cuenya.

Read more

Metamaterial multiverse

Post by Igor I. Smolyaninov, Department of Electrical and Computer Engineering, University of Maryland.

How to build a ‘multiverse’ in a lab

Many physical properties of our universe, such as the relative strength of the fundamental interactions and the value of the cosmological constant appear to be fine-tuned for the existence of human life. One possible explanation of this fine tuning assumes the existence of a multiverse, which consists of a very large number of individual universes with different physical properties. Intelligent observers populate only a small subset of these universes, which are fine-tuned for life.

While this point of view may not be falsifiable based on astrophysical observations, one possible way to ascertain its viability may rely on macroscopic electrodynamics and condensed matter physics. In particular, the ‘optical spacetime’ in electromagnetic metamaterials (artificial structures patterned on a subwavelength scale to achieve unusual materials parameters) may be engineered to mimic the landscape of a multiverse that has regions with different topology and effective dimensionality. Nonlinear optics in metamaterials in these regions mimics Kaluza-Klein theories with one or more kinds of effective charges [1].

Another closely related model of a cosmological multiverse may be based on the electromagnetic properties of ferrofluids [2]. When a ferrofluid is subjected to a modest magnetic field, the nanoparticles inside the ferrofluid form small hyperbolic metamaterial domains, which from the electromagnetic standpoint behave as individual ‘Minkowski universes’. Microscopic spacetime defects and inflation-like behaviour appear to be generic within these individual Minkowski domains. It is remarkable that these non-trivial effects are accessible to direct experimental visualization using optical microscopy. Here I summarize several metamaterial systems that capture many features of cosmological models and offer insights into the hypothesized physics of the multiverse.

Electromagnetic metamaterials and transformation optics

The unconventional functional behaviors of the electric permittivity ε and magnetic permeability μ in metamaterials in the physical space lead to the creation of unusual ‘optical spaces’ that can be designed and engineered at will, opening the possibility of controlling the flow of light with nanometer spatial precision. Moreover, in a special class of hyperbolic metamaterials the optical space behaves like an ‘optical spacetime’, in which one of the spatial dimensions assumes a time-like character [3]. Hyperbolic metamaterials are extremely anisotropic electromagnetic materials, which behave like a metal in one direction and like a dielectric in the orthogonal direction. Hyperbolic metamaterials are typically composed of multilayer metal-dielectric or metal wire array structures. While in ordinary media all components of the ε tensor are positive, in hyperbolic metamaterials they have opposite signs in the orthogonal directions across quite broad hyperbolic frequency bands. Light can still propagate in such materials, but the direction of negative ε becomes time-like, so that the normally Euclidean optical space behaves more like a Minkowski spacetime at these frequencies. Light rays in this situation start to behave like evolving ‘world lines’.

 Modeling time with metamaterials: metamaterial models of the Big Bang

The nature of time has been a major subject of science, philosophy and religion. Our everyday experiences tell us that time has a direction. On the other hand, most laws of physics appear to be symmetric with respect to time reversal. A few exceptions include the second law of thermodynamics, which states that entropy must increase over time, and the cosmological arrow of time, which points away from the Big Bang. While it is generally believed that the statistical and the cosmological arrows of time are connected, we cannot replay the Big Bang and prove this relationship experimentally. However, it appears that electromagnetic metamaterials may provide us with interesting tools to better understand this relationship and, maybe, the physical origins of time itself. For example, an experimental demonstration of the behavior of a world line near a toy Big Bang in an expanding metamaterial universe as a function of a timelike radial r coordinate can be seen in Figure 1.

Figure 1 : (a) Atomic force microscopy image of a hyperbolic metamaterial structure. (b)  Light rays increase their separation as a function of a timelike radial coordinate. Light scattering at the edges of the structure is partially blocked by semi-transparent triangles. (c) Schematic view of world lines behavior near the cosmological Big Bang.

Light rays are launched into the hyperbolic metamaterial near the r=0 point via the central phase matching structure (marked with an arrow in the figure). Similar to the world line behavior near the Big Bang (Fig. 1c), light rays or ‘world lines’ indeed increase their spatial separation as a function of a ‘timelike’ radial coordinate. This experimental model may illustrate the relationship between the statistical and the cosmological arrows of time if disorder is introduced in this metamaterial structure [3].

Metamaterial multiverse experiments in ferrofluids    

Let us now turn our attention to self-assembled hyperbolic metamaterials made of ferrofluids, which share some common features with the class of cosmological models of the multiverse based on the loop quantum gravity [4]. This analogy relies on the fact that a modest external magnetic field aligns most of the individual magnetic nanoparticles in the ferrofluid into long parallel chains, so that the ferrofluid becomes a self-assembled hyperbolic metamaterial [5]. It appears that both loop quantum gravity models and the hyperbolic metamaterials may exhibit metric signature phase transitions [4], during which the spacetime metric used to describe the system changes its signature. Moreover, the metric signature transition in a ferrofluid leads to separation of the optical spacetime into a multitude of intermingled Minkowski and Euclidean domains, giving rise to a ‘metamaterial multiverse’ [2]. Inflation-like behaviour appears to be generic within the individual Minkowski domains (Fig. 2). Thus, studies of the optical spacetime in ferrofluids may illustrate the potential existence of parallel universes and shed some light on the ‘measure problem’ in a multiverse, which has to do with making probabilistic predictions of some particular measurement outcomes in a multiverse setting. All these effects may be studied in ferrofluids via direct microscopic observations.

Figure 2: (a) This magnified image of the Minkowski domains in a ferrofluid illustrates inflation-like expansion of the optical spacetime near the domain wall. (b) Measured and calculated  dependencies of the spacetime scale factor on the effective time.

Microscopic observation of spacetime melting in ferrofluids

Recent developments in gravitation theory provide numerous clues that strongly indicate that classic general relativity is an effective macroscopic theory, which will be eventually replaced with a more fundamental theory based on yet unknown microscopic degrees of freedom.  Unfortunately, these true microscopic degrees of freedom cannot be probed directly.  Our ability to obtain experimental insights into the future microscopic theory is severely limited by the low energy scales available to terrestrial physics and even to astronomical observations. In order to circumvent this problem, it is instructive to look at various examples of emergent gravity and analogue spacetimes [6] that appear in solid state systems such as superfluid helium, electromagnetic metamaterials and cold atomic Bose-Einstein condensates.

As discussed above, ferrofluids subjected to an external magnetic field have emerged as an interesting example of an electromagnetic metamaterial, which exhibits gravity-like nonlinear optical interactions, and which may be described by an emergent effective Minkowski spacetime. Unlike other more typical metamaterial systems, such a macroscopic self-assembled 3D metamaterial, they may also exhibit physics associated with topological defects and phase transitions. In particular, effective Minkowski spacetime melting may be observed and visualized in these metamaterials. If the magnetic field is not strong enough to hold nanoparticle chains together, the optical Minkowski spacetime gradually melts under the influence of thermal fluctuations. It may also restore itself, if the magnetic field is increased back to its original value. Such a direct microscopic visualization of Minkowski spacetime melting is depicted in Figure 3.

Figure 3: Magnified quasi-3D images taken from a movie of the effective Minkowski spacetime melting in a ferrofluid. A small region in the third frame, which remains in a microscopic Minkowski spacetime state (while the rest of the original spacetime has already melted) is highlighted by the yellow circle.


The mutually related fields of electromagnetic metamaterials and transformation optics are experiencing extremely fast progress. While most of the experimental and theoretical work in these fields is devoted to revolutionary practical devices, such as super-resolution microscopes and electromagnetic invisibility cloaks, I have tried to show that they also have enormous potential in helping to shed light on some of the most fundamental problems of philosophy and science, such as the nature of time or potential existence of alternative universes. While the metamaterial systems considered here may or may not have anything in common with the real physical universe, they may still teach us a lot about the fundamental physics governing it.


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  2. I. I. Smolyaninov, B. Yost, E. Bates, V. N. Smolyaninova, Optics Express 21, 14918 (2013).
  3. I. I. Smolyaninov, Y. J. Hung, JOSA B 28, 1591 (2011).
  4. M. Bojowald, J. Mielczarek. J. of Cosmology and Astroparticle Phys. 08, 052 (2015).
  5. V.N. Smolyaninova, et al. Scientific Reports 4, 5706 (2014).
  6. C. Barcelo, S. Liberati, M. Visser, Living Rev. Relativity 8, 12 (2005).


Interactions: Beatriz Roldán Cuenya

Beatriz Roldán Cuenya is the Director of the Interface Science Department at the Fritz Haber Institute of the Max Planck Society, Berlin, Germany.

What did you train in? What are you working on now?

My undergraduate training was in Physics with a minor in Materials Science in Spain. Subsequently I did my PhD in Solid State Physics in Germany and from there I transitioned to a postdoctoral position at a Chemical Engineering Department in the United States. Currently, I am working at the interface between physics and chemistry investigating thermal and electro-catalytic processes taking place over nanostructured materials. My group’s research program takes advantage of in situ and operando microscopy and spectroscopic characterization methods (including synchrotron-based techniques) for the understanding of correlations between material properties such as chemical reactivity and specific structural, electronic and chemical characteristics of the system.

What did you find most difficult when you started working in an area out of your comfort zone?

Missing basic chemical concepts and nomenclature that a physicist does not acquire during his/her undergraduate training, but are essential for the understanding of chemical processes taking place at gas/liquid/solid interfaces. This motivated a slow literature review since I had to stop often to go back to basic undergraduate books before being able to dig deeper into the current literature. However, the strong mathematics background that is inherent part of a physicist’s training was very helpful when dealing with some of the topics in the department of Chemical Engineering I transferred to.

And what did you find most helpful to familiarize yourself with new concepts and jargon?

Reading the related literature, specifically review articles, while having side by side undergraduate chemistry books.

Tell us about your experience the first time you went to a conference outside the field you trained in.

It was exciting because there were a lot of new things to learn, but also somewhat frustrating since there were at times gaps of knowledge that prevented me from understanding a significant fraction of the content presented.

What are the main challenges and the main advantages of working in an interdisciplinary team?

The main challenge I found was to convince the scientific communities you are interacting with, in my case, physicists, chemists and chemical engineers, that you can contribute meaningful new research ideas and findings to their respective fields even without a formal undergraduate training in such field. It was also difficult to recruit students from the different disciplines, the physicists in my department were scared to join the group because I did “too much chemistry” and the chemists were concerned that they could not follow the math or that they did not have sufficient background in specific topics such as quantum mechanics or electrodynamics.

The advantage was that once you managed to build an interdisciplinary team, the boundaries soften and the student and postdocs end up working in a much richer environment where accelerated knowledge transfer is favoured. We managed to become a self-sufficient group by teaming up chemists that were in charge of sample synthesis and for example electrochemical characterization, chemical engineers contributing to our reactor design and thermal catalysis work, and physicists providing microscopy and spectroscopic tools for the characterization of our catalytic materials.

What would be your advice to a PI leading an interdisciplinary group?

To try to get joint appointments in the different departments of interest to foster student recruitment and the exchange of ideas with other faculty colleagues. If possible, this should include teaching some advanced courses or given some introductory presentation as guest lecturer in the partner department.

Do you find it particularly difficult to obtain funding? Or to get your research published?

Actually yes, this was the case at first. When I was an assistant professor in Physics in the United States it was difficult to convince the external reviewers in Chemistry or Chemical Engineering departments that even though my background was different, I still had the required expertise to bring to success a given interdisciplinary project. I found that chemists are more comfortable reviewing/funding chemists and same for physicists, especially when you attend mixed review panels at science foundations. However, as an assistant professor in Physics my first grant came from the American Chemical Society (Petroleum Research Fund) and the second, a CAREER award from the National Science Foundation, was granted by the Materials Research Division in the sub-area of Solid State Chemistry.

I faced the same difficulties when trying to publish in chemistry-oriented journals while submitting papers with a Physics Department affiliation. Nevertheless, with time and as visibility improved I managed to establish good connections in both communities and get invitations to present my work in both communities, which will in return facilitated publication in the top journals of both fields.

Is there any anecdote you would like to share?

I recall the frustration of being a female assistant professor in physics struggling to convince editors in chemistry-related fields to send out your work for external peer-review. I learned the hard way that when a more senior collaborator in the “correct” scientific disciple was added to the co-author list the paper would be easily sent out for review and subsequently published, while when similar quality work was submitted directly by myself it was almost never considered by the top journals. That is a serious issue since it might end up encouraging junior people with innovative ideas not to stand up on their own but seek for “strong senior supporters” to champion a given paper to get into the system (a given journal database) with the end result being that the real contribution of the junior person might be questioned.