Matthias Christandl

• Presentation
• Research outputs
• Most downloaded

I am hiring!

We have an exciting environment for quantum information science in Copenhagen! If you are interested in working as a PhD student and postdoc, just send me an email. Official calls for PhD students and postdocs are administered through my department every Fall (Phd and postdoc) and Spring (PhD only).

About me

I am Professor in the Department of Mathematical Sciences at the University of Copenhagen, Center Leader of the Quantum for Life Center funded by the Novo Nordisk Foundation and co-PI of the VILLUM Foundation research centre QMATH, the Centre for the Mathematics of Quantum Theory. I am also heading the UCPH Quantum Hub, a cross-departmental and cross-faculty collaborative initiative.

Previously, I was Assistant Professor at ETH Zurich (2010–2014) and at the University of Munich (2008–2010), and Postdoctoral Fellow at the University of Cambridge (2005–2008). I hold a PhD from the University of Cambridge (2006) and a Diploma from ETH Zurich (2002). 

In 2013, I was awarded an ERC Starting Grant and in 2018 an ERC Consolidator Grant. In 2016 I was elected to the Royal Danish Academy of Sciences and Letters. In 2018, I was on sabbatical at MIT for one semester while serving as programme committee chair for QIP 2019, the premier conference in the field of quantum information processing.

My research 

My research aims to understand the way quantum mechanics impacts on information processing. To this end, I have made contributions of an algorithmic, cryptographic, information-theoretical and foundational nature, drawing on techniques and concepts from mathematics, computer science, physics and engineering. 

Excited by recent experimental breakthroughs in the building of quantum devices, I continue this theoretical line of research with a focus on the near-term facilitation and long-term benefits of quantum computing.

You find all my publications (including preprints) here and all recent presentations here. You can also find many talks that I have given on youtube.

Key results

• Quantum position verification (Nature Physics 2022)
• Quantum communication with noisy devices (IEEE Transactions in Information Theory 2022)
• Limitations of quantum repeaters (Nature Communications 2015)
• Entanglement verification of quantum devices (Science 2013).
• Fast algorithm for the quantum separability problem (STOC 2011, Communications in Mathematical Physics 2011)

Further research on quantum mechanics, tensors, and complexity

The quantum states of several particles can be described mathematically with the help of tensors (higher-dimensional arrays of numbers, generalising matrices). Through this connection, I have obtained fundamental results in the theory of tensors, as well as applications to condensed matter physics (via tensor networks) and algebraic complexity theory. Algebraic complexity is a topic in classical computer science that includes the famous problem of deciding whether matrices can be multiplied in quadratic time. My work here may be regarded as quantum-inspired classical algorithmic research.

Key results

• Reducing the bond dimension in tensor networks (Phys. Rev. B 2021)
• Universal obstructions to tensor transformations (JAMS 2023, FOCS 2018)
• Efficient algorithm for multiplicities occurring in approach to solving P versus NP (STOC 2012), implemented here.