# Theory

QIFT stands for Quantum Information, Foundations, and Technologies. And this already gives you a first taste of our approach. First of all, we conduct research in Quantum Information. In short: this means that we explore new ways to process information made possible by the puzzling laws of quantum mechanics. A major focus in our work is the optimized design of quantum devices that make the best use of limited resources. We ask questions like:

• How well can we read out a signal encoded in the quantum state?

• How well can a quantum particle indicate a moment in time or a direction in space?

• What is the minimum amount of energy needed to implement a desired computation?

We tackle these and many other fundamental questions with a variety of techniques, ranging from group theory to semidefinite programming and convex analysis. In fact, developing new optimization techniques for quantum information processing is one of the contributions we are proud of!

Quantum Foundations. Being familiar both with quantum advantages and quantum limitations, we are also compelled to understand what makes quantum information so special. Where does the power of quantum computers come from? What makes quantum cryptography secure? Can reduce the variety of quantum information protocols to a few simple principles?

Searching for high-level principles for quantum protocols is one of the main lines of our foundational research. We believe that, once the basic principles have been identified, inventing new quantum protocols and new quantum devices will become easier and more intuitive. Moreover, our research on the foundations gives us a unique opportunity to share the beauty of quantum mechanics with a broader public and to transfer fresh new knowledge from academia to society.

Our foundational activity is not limited to the search of high-level principles for quantum information. A more ambitious programme is to turn such principles into a foundation for the whole of quantum physics. Our approach is inspired by the motto “Quantum foundations in the light of quantum information”, coined by Gilles Brassard and Chris Fuchs. Sometimes, quantum information offers a new perspective on old questions on quantum mechanics, while some other times it motivates entirely new questions. And sometimes, thinking about foundations can lead us to the discovery of new quantum effects and to the design of new information protocols.

For us, exploring the foundations is not a pastime, but rather a method—a way to expand the impact of quantum information and to highlight its connections with other exciting areas of physics and computer science.

Quantum technologies. Our investigations into the roots of quantum information is complemented by an interest in technological applications, especially in quantum optics. In the past few years, we analyzed experiments on new quantum technologies, such as quantum teleportation, squeezing, amplification, and purification. We developed a set of "quantum benchmarks", that is, tests that can be used to judge the performances of realistic devices. Combined with the optimal quantum protocols, the quantum benchmark indicate provide an ideal standard for the design of future experiments.

Working on an emerging technology, we strongly desire to see the object of our research make an impact in the real world. Sometimes it turns out that the optimal devices predicted theoretically cannot be easily implemented in practice. But even in those cases, knowing the ultimate in-principle limits is important, as it can serve as a compass indicating the direction for the next technological advancements. Even the most foundational layers of our research eventually aim to make a real-world impact, by identifying new working principles for the construction of quantum algorithms and communication systems, and by expanding the application of quantum technologies to the simulation of new exotic physics.

History: Our group started out at the University of Erlangen-Nuremberg in 2001 (though it has roots to the Helsinki Institute of Physics from 1997), and relocated to the Institute of Quantum Computing at the University of Waterloo in 2006.

Our position in the research landscape: Our group explores the interface between quantum communication theory and quantum optical implementations.

we translate between abstract protocols (described by qubits) and physical implementations (described for example by laser pulses)

we benchmark implementations to properly characterize quantum advantage

we exploit quantum mechanical structures for use in quantum communication

Fields to which are group contributes:

Quantum Key Distribution: Theory for Applications

Quantum Repeater

Protocols with quantitative quantum advantage

Linear Optics

Entanglement Verification

Research Philosophy: As we work on our research topics, we also find often the need to extend the theoretical structures of quantum information theory to answer deeper underlying questions. These include for example which type of observed data can be turned into secret key? How to characterize symmetric extendibility of bi-partite quantum systems? How to verify entanglement from incomplete data in large Hilbert spaces?

When approaching a research question, it is our approach to concentrate on the development of tools, so that these tools answer the research question, and can also be used to answer other questions. This is in contrast to brute force methods that only solve the one problem at hand.

On our web pages you will be able to find more detailed information about our research outcomes, our current research direction and also about the opportunities to join our group.

Our group deals with theoretical and computational atomic, molecular, and optical (AMO) physics with primary interest in the physics of Bose-Einstein condensates.

The freshly created group of Giulia Ferrini investigates quantum information protocols with continuous variables, with a special focus on quantum computation and quantum advantage, from the theoretical point of view. Strong collaborations with the group of Göran Johansson and the one of Per Delsing and Jonas Bylander, dealing with superconducting Josephson junctions at Chalmers (theory and experiments respectively), are being developed.

Skolkovo Institute of Science and Technology (Skoltech) is a unique English-speaking international graduate only research university located in Skolkovo, just outside of Moscow. Established in collaboration with M.I.T., Skoltech is an integral part of the Skolkovo Innovation Center that comprises a complete high-tech city with a number of international R&D centers and start-up incubators, several of which are focused on quantum technology.

Skoltech's Quantum Software Initiative is lead by Jacob Biamonte.

Planned research projects have an applied mathematical and numerical analysis flavor and focus more generally on the foundations of (i) non-stoquastic quantum annealing, (ii) quantum enhanced machine learning algorithms, (iii) quantum tensor network methods and (iv) the interrelations between tracks (i), (ii) and (iii). The group has access to large-scale computing facilities.

Skoltech has a research portfolio covering a range of quantum and machine learning technologies. This includes the Quantum Polariton Simulators Group by Pavlos Lagoudakis and Natalia Berloff as well as the Tensor Networks for Machine Learning Group by Ivan Oseledets and Andrzej Cichocki.

QUANTUM RESOURCES OF COMPOSITE OPEN SYSTEMS FOR APPLICATIONS IN QUANTUM INFORMATION

Quantum coherence, entanglement, non-locality are different types of quantum features of systems at microscopic scale which are basic resources for the upcoming disruptive quantum information technologies. The latter, including quantum communication architectures and quantum computers, are expected to significantly improve the everyday lives of ordinary people around the world. The complete knowledge and control of the quantum resources present in many-particle systems is thus a fundamental requirement towards this achievement. A reliable use of quantum-enabled devices must also overcome the big issue of the detrimental effects induced by the surrounding environment which destroy the desired quantum properties. This research topic aims at devising strategies for the generation, characterization and observation of quantum coherence and correlations, such as entanglement, in different scenarios, like cavity and circuit quantum electrodynamics, quantum optics, solid state and condensed matter. Moreover, we intend to investigate the dynamics of these quantum features to stimulate proposals for their efficient preservation against the environment-induced decay. Special attention will be devoted to systems of identical particles (e.g., photons, electrons, atoms), whose faithful description has remained long debated, for which we have developed a new non-standard approach which is expected to provide novel results regarding the utilization of entanglement due to quantum indistinguishability.

The research group addressing these lines is led by Dr. Rosario Lo Franco at the University of Palermo, Italy. The group collaborates with several other leading research teams and researchers worldwide, both theoretical and experimental.

We are a young research group within the Centre for Theoretical Atomic, Molecular, and Optical Physics at Queen’s University Belfast. We work on quantum information processing, quantum optics, quantum thermodynamics, and the physics of many-body quantum systems. Our interests are many and quite variegate: the group offers a widespread expertise in many topics!

We collaborate with experimentalists and theorists alike: some of us are even able to enter a lab without making any damage! Our international dimension is reflected in the make-up of the team.

If you are interested in our work or in joining us, please contact Alessandro Ferraro, Gabriele De Chiara, or Mauro Paternostro.

Our group is pleased to announce the master’s programme: Quantum Information Technologies The main goal of this programme is to educate and train highly-qualified specialists who will be able to solve complex problems related to the transmission, storage, and processing of data using quantum-information technologies. Furthermore, graduates of the programme will be able to use cutting-edge technologies and directly take part in their development.