About me

I am currently (since March 2017) a Senior Postdoc at the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna in the group of Marcus Huber.
As of August 2018 I am leading research in the FWF Stand-Alone Project "Resources for flexible quantum information processing" (P 31339-N27), which will investigate the interplay, conversion, and flexible use of resources for quantum computation, quantum metrology, and quantum thermodynamics.
My research interests lie in the overlap of quantum information & computation with  quantum optics and quantum thermodynamics. Recently, I have been interested in investigating the connections between resources for quantum computation and quantum metrology. See the Research Section of my homepage for more details.

Previously, I have worked as a Postdoc (Universitätsassistent) at the Institute for Theoretical Physics of the University of Innsbruck, working in the Quantum Information & Computation group with Prof. Hans J. Briegel, where I have also been teaching courses in theoretical physics. I obtained my PhD (2010-2013) under the supervision of Ivette Fuentes at the University of Nottingham. Before that, I worked in the particle physics group at the Faculty of Physics at the University of Vienna, where I studied for my diploma, supervised by Reinhold A. Bertlmann.
Contact
Nicolai Friis
Senior Postdoc
Institute for Quantum Optics and Quantum Information
Austrian Academy of Sciences
Boltzmanngasse 3
1090 Vienna, Austria
Tel.: +43 1 4277-29566
e-mail: nicolai.friis@univie.ac.at

News

Thermodynamics implies that measurements are non-ideal and require an input of energy. In our paper `Work estimation and work fluctuations in the presence of non-ideal measurements', we explore the consequences of non-ideal measurements for work estimation [T. Debarba, G. Manzano, Y. Guryanova, M. Huber, and N. Friis, New J. Phys. 21, 113002 (2019), arXiv:1902.08568].
Correlations have an energy cost that we investigate in our new paper: Thermodynamically optimal creation of correlations [F. Bakhshinezhad, F. Clivaz, G. Vitagliano, P. Erker, A. T. Rezakhani, M. Huber, and N. Friis, J. Phys. A Math. Theor. 52, 465303 (2019), arXiv:1904.07942]. In particular, we present mathematical tools for determining the existence of symmetrically thermalizing unitaries necessary saturate entropic bounds on the energy cost of correlations.
Our review "Trade-Off Between Work and Correlations in Quantum Thermodynamics" has been published as a chapter in: Thermodynamics in the Quantum Regime, Chapter 30, edited by F. Binder, L. A. Correa, C. Gogolin, J. Anders, and G. Adesso (Springer 2019) [arXiv:1803.06884].
In our latest paper out on the arXiv [H. Poulsen Nautrup, N. Delfosse, V. Dunjko, H. J. Briegel, and N. Friis, arXiv:1812.08451], we present a reinforcement learning approach for optimizing and adapting quantum error correction codes.
Picture
Image credit: Christian Murzek 2018
Every wondered about the different worlds inhabited by theorists and experimentalists? Find out more in this wonderful blog post about our new review paper "Entanglement certification from theory to experiment", fresh out in Nat. Rev. Phys. 1, 72-87 (2019).
Our paper entitled "Speeding-up the decision making of a learning agent using an ion trap quantum processor", has now been published in Quantum Science and Technology. We report on a first proof-of-principle experiment demonstrating a quantum speed-up in the deliberation time of quantum learning agents w.r.t. to their classical counterparts [Sriarunothai, Wölk, Giri, Friis, Dunjko, Briegel, Wunderlich, Quant. Sci. Techn. 4, 015014 (2019), arXiv:1709.01366].
 Our experiment & theory collaboration paper "Measurements in two bases are sufficient for certifying high-dimensional entanglement" has appeared online in Nat. Phys. 14, 1032 (2018) [earlier version available at arXiv:1709.07344].

In this work, we develop efficient new techniques for certifying high-dimensional entanglement using measurements in only two bases. We demonstrate the usefulness of this method: we certify 9-dimensional entanglement of two photons entangled in their orbital angular momentum. (Image credit: upper: Mehul Malik, lower: IQOQI Vienna/Harald Ritsch)
Ideal projective measurements are a convenient fiction but non-ideal measurements can approximate them at finite energy cost. Find out more in our recent preprint

Y. Guryanova, N. Friis, and M. Huber, Ideal Projective Measurements Have Infinite Resource Costs, e-print arXiv:1805.11899 [quant-ph] (2018).
The second installment of our investigation of the usefulness and limitations of Gaussian operations in quantum thermodynamics is now available on the arXiv: Precision and Work Fluctuations in Gaussian Battery Charging, has now been published in Quantum 2, 61 (2018).
In a recent collaboration with Innsbruck and Ulm, we have been able track the dynamics of the development of genuine multipartite entanglement in groups of up to 5 neighbours in a chain of 20 fully controlled trapped-ion qubits. The paper hast just been published in Physical Review X [Friis, Marty et al., Phys. Rev. X 8, 021012 (2018)]. (Image credit: IQOQI Innsbruck/Harald Ritsch)

Press release from IQOQI Innsbruck (English),
Phys.org (English), IEEE Spectrum (English)
Austrian news (in German): ORF & der Standard
Our paper on "Flexible resources for quantum metrology", New J. Phys. 19, 063044 (2017) [arXiv:1610.09999], discussing how 2D cluster states can be used as resources for parameter estimation, has been selected by the editors of New Journal of Physics for inclusion in the 'Highlights of 2017' collection.
I feel very honored and happy to have been selected as the recipient of the Entropy 2018 Young Investigator Award. On this occasion I will give a talk at the conference “Entropy 2018: From Physics to Information Sciences and Geometry”.
I have recently joined the International Editorial Board of the Journal of Physics Communications by IoP. The journal is fully open access and is committed to rigorous peer review assessing the scientific quality and ensuring that contributions advance the respective research areas but explicitly allows for the inclusion of negative or null results and replication studies. 
Read about an exciting new method to transfer quantum information between quantum memories and quantum processors in "Fault-tolerant interface between quantum memories and quantum processors" which was just published in Nat. Commun. 8, 1321 (2017) [arXiv:1609.08062].

Press release from the University of Innsbruck (English)
Austrian news (in German): ORF Tirol & der Standard
Phys.org coverage (English)
IEEE Spectrum Article (English)
"Geometry of two-qubit states with negative conditional entropy", our recent paper contrasting a variety of different entanglement detection criteria geometrically, has been published in J. Phys. A: Math. Theor. 50, 125301 (2017) [arXiv:1609.04144].

Update: The article is now fully open access.
Our new article on quantum thermodynamics entitled "Passivity and practical work extraction using Gaussian operations" has been published in the New Journal of Physics: New J. Phys. 18, 113028 (2016) [arXiv:1608.04977].