**Professor Gerardo Adesso is a theoretical physicist and Professor of Mathematical Physics at the ****School of Mathematical Sciences****, ****The University of Nottingham****. He is also a member of the ****Editorial Board**** of ****Journal of Physics A: Mathematical and Theoretical****. He works on a number of topics relating to quantum information theory, specifically the characterisation of quantum coherence and correlations and their applications to quantum technologies. We talk to him about his career, current research and what it is he finds so appealing about the topics he studies.**

**Could you provide us with a brief summary of your career so far? **

I fell in love with quantum mechanics during my undergraduate studies in Physics at the University of Salerno, Italy. I furthered my interests in the field during a PhD also at Salerno, which I completed in 2007. The PhD included a year-long research experience at DAMTP, University of Cambridge which helped me to explore the breadth of quantum information science and its applications. My PhD research focused on the quantification of entanglement in continuous-variable quantum systems, a subject in which I am now regarded as a leading expert. Results from my PhD were summarised in a Topical Review on J. Phys. A which has attracted over 200 citations. After a brief post-doctoral experience at Universitat Autonoma de Barcelona, I moved to the University of Nottingham as a Lecturer in January 2009. Quantum information research at Nottingham has expanded considerably after my appointment. I am now a Professor (from 2016) and head of a research team of 1 junior staff member, 3 postdocs, 7 PhD students, and several long-term visiting scientists, under the umbrella of the newly established Centre for the Mathematical and Theoretical Physics of Quantum Non-Equilibrium Systems.

**You have done a degree of work on Quantum Correlations. What other research areas are of interest to you and what led you to this area of research?**

I have been fascinated by entanglement since first learning about it during my university studies. My recent research, supported by an ERC Starting Grant (2015-2020), has been pioneering in unveiling resources for quantum technology that are more general than entanglement, yet more robust against noise. Such a novel take on quantum correlations, which challenged the two-decade-old separability paradigm, and which I advanced trough several collaborations with theoretical and experimental groups, attracted increasing interest to my work. This progress is presented in another Topical Review on J. Phys. A. I have now contributed key advances to the study of all forms of nonclassical correlations (including entanglement, discord, steering, and nonlocality) and quantum coherence in composite systems. For all these quantum resources, I have proposed faithful measures and discovered operational interpretations, in some cases demonstrated in laboratory.

More generally, I am interested in understanding the elusive boundary between classical and quantum description of the world. This spans from recognising signatures of genuine quantumness in increasingly complex systems, to identifying specific tasks where such resources provide a performance enhancement. These tasks include quantum communication, control, sensing and metrology. I am also working on thermodynamics at the quantum regime, in particular the design and performance optimisation of nanoscale heat engines and refrigerators. Some of my most exotic research plans delve into foundational questions such as how the objectivity of classical information emerges from the subjectivity of quantum observers, and at which rate.

**What kind of problems appeal to you?**

I am fascinated by various types of problems. Sometimes, I find it satisfactory to complete the proof of a rather abstract mathematical theorem, which has nonetheless concrete applications in seemingly unrelated branches of physics. For example, applications of linear algebra and symplectic geometry tools to the characterisation of quantum correlations in harmonic systems are very appealing to me, see e.g. this recent Letter on J. Phys. A and its follow-ups. I am progressively more attracted towards questions challenging the conventional beliefs of quantum information theory, such as where to draw the line between useful and useless resources to demonstrate a quantum supremacy over classical schemes. Sometimes, on the other hand, I like to think of a very concrete problem, such as the performance optimisation of a practical device. In general, whenever a problem admits a neat analytical solution, this makes me particularly happy, but I often resort to numerical explorations in order to guess the solution in the first place. Then, it is usually a challenge for my junior collaborators to prove my intuition right. There have been cases where my intuition failed spectacularly, and investigating such failures turned out to spark a whole new series of interesting questions. This happened e.g. when considering a particular “monogamy” inequality for multipartite entanglement which I had been conjecturing for many years, whose hard-to-find violations eventually revealed a new method to quantify entanglement exactly by simple methods of Euclidean geometry. You can read more about this on my blog.

**What are you currently working on?**

I had a revival of interest on continuous-variable quantum information theory and applications, as I realised there are still a series of unsolved problems where I can contribute, and which rely on interesting mathematical connections that I was not able to reveal during my PhD. In parallel, I am working on the general structure of quantum resource theories, focusing in particular on quantum coherence. The field is rapidly growing (see e.g. my recent review) and is a simple yet important test-bed for both quantum foundations and quantum technologies. I am also focusing on applied and engineering-oriented problems of quantum enhanced imaging and metrology, quantum thermometry and thermodynamics.

**What do you consider to be the most significant problems to be addressed in your field?**

We need to be able to develop a general method to identify resources useful for quantum technologies, and how to exploit them optimally to maximise the efficiency of concrete applications. There are so many different protocols relying on different nonclassical phenomena, yet we still lack a unifying framework. I believe new methods will need to be delivered to address systematically the design and optimisation of new quantum information and communication tasks. The more we understand what makes quantum resources fundamentally different from classical ones, the more we get inspired with effective blueprints to take advantage of them in relevant problems and in realistic scenarios.

**What are the challenges facing researchers in mathematics and theoretical physics?**

I am a physicist in a School of Mathematical Sciences. Sometimes, my publications (e.g. in Physical Review Letters) are perceived as too “physicsy” for the standards of my department. On the other hand, my results usually contain technical bits which are not judged favourably by some higher-impact Physics journal. It is sometimes hard to strike a balance. However, this is a useful challenge for me. I strive quite a lot to craft the presentation of my papers so as not to compromise on rigour on one hand, and to make my results accessible and appealing to a broad audience on the other hand. Dissemination via blog posts and media outlets such as Phys.org and New Scientist help to reach a wider readership, provided the science is not too distorted in such communications. I find it very stimulating to be able to draw from and contribute to both Maths and Physics in my inter-disciplinary field of research. I am sure other researchers in similar crossroads area can be equally challenged and stimulated. In general, the boundary between applied mathematics and theoretical physics is quite blurred anyway, and rightly so.

**Where do you think your research will take you next? Are there any other fields you are interested in exploring?**

I hope I will come closer to understand deep foundational aspects of quantum mechanics, and what are its ultimate limits of applicability. This may possibly give me a glimpse of what lies beyond. I am also very attracted to other emerging technologies, such as additive manufacturing and machine learning. Whether a successful hybridisation and cross-fertilisation of these areas with quantum enhanced technologies is possible in concrete terms, would be a question I’d like to consider in the near future.

**Finally, do you have any advice for young researchers entering the field?**

Do what you love and love what you do. Follow your passion and be sure you find the fun in research, despite all frustrations. Do not get discouraged by the struggles of academia. There are plenty of success stories! Also, do not be afraid to switch fields or evolve your beliefs. As I argued recently in *Nature*, pivoting is pivotal to achieve impact!

On behalf of Journal of Physics A I would like to thank Professor Adesso for his work as a board member and for taking the time to talk to us.

**Read more:**

- Topical review: Measures and applications of quantum correlations
- Strong subadditivity for log-determinant of covariance matrices and its applications
- Entanglement in continuous-variable systems: recent advances and current perspectives

This work is licensed under a Creative Commons Attribution 3.0 Unported License

Front image and image 1: Copyright Samanta Piano; used with permission. Not covered by CC-BY 3.0.

Categories: Journal of Physics A: Mathematical and Theoretical