Quantum Computing and Information Processing

Our mission is to investigate complex quantum systems, engineer novel devices and educate students to advance quantum technologies for scientific and societal impact.
Recent projects
Stefan Filipp, Max Werninghaus, Federico Roy
Stefan Filipp, Franz Haslbeck, Federico Roy
Stefan Filipp, Ivan Tsitsilin
Stefan Filipp, Malay Singh
Rudolf Gross, Stefan Filipp, Frank Deppe, Hans Huebl, Matthias Althammer, Qi-Ming Chen, Frank Deppe, Kirill Fedorov, Florian Fesquet, Kedar Honasoge, Achim Marx, Yuki Nojiri, Michael Renger, Nadezhda Kukharchyk, Stephan Geprägs, Thomas Luschmann, Ana Strinic
Stefan Filipp, Stefan Filipp, Rudolf Gross, Frank Deppe, Kirill Fedorov, Hans Huebl, Achim Marx, Martin Knudsen, Franz Haslbeck, Leon Koch, Federico Roy, Johannes Schirk, Malay Singh, Ivan Tsitsilin, Max Werninghaus, Johneph Sukham †
Rudolf Gross, Frank Deppe, Stefan Filipp, Rudolf Gross, Hans Huebl, Nadezhda Kukharchyk
Rudolf Gross, Frank Deppe, Stefan Filipp, Rudolf Gross, Hans Huebl, Nadezhda Kukharchyk
Recent publications
Max Werninghaus and Daniel Egger and Stefan Filipp
Research Article | Physical Review X Quantum 2, 020324  (2021)
Max Werninghaus and Daniel J Egger and Federico Roy and Shai Machnes and Frank K Wilhelm and Stefan Filipp
Research Article | npj Quantum Information 7, 14  (2021)
M. Ganzhorn, G. Salis, D. J. Egger, A. Fuhrer, M. Mergenthaler, C. Müller, P. Müller, S. Paredes, M. Pechal, M. Werninghaus, and S. Filipp
Research Article | Physical Review Research 2, 033447  (2020)
J M Fink and R Bianchetti and M Baur and M Göppl and L Steffen and S Filipp and P J Leek and A Blais and A Wallraff
Research Article | Physical Review Letters 103, 083601--4  (2009)
S Filipp and J Klepp and Y Hasegawa and C Plonka-Spehr and U Schmidt and P Geltenbort and H Rauch
Research Article | Physical Review Letters 102, 030404  (2009)

Technological progress goes hand in hand with incessant advances in computing power. Modern personal electronic devices have the computational power of a supercomputer from just a decade ago. Computer-aided designs, logistics, data analysis and cognitive computing have become an essential part of modern life. However, current progress in down-scaling transistors reaches physical limits when approaching atomic scales, and heat dissipation becomes a severe issue with increasing transistor densities.

Above all, certain complex physical problems such as computing energy spectra, correlations or time dynamics in molecular and condensed matter systems are beyond the reach of classical computers. Because of the exponential growth of Hilbert space with the number of particles, such computations require exponential resources preventing the computation of realistic systems.

A quantum computer may provide the means to compute ground-state energies, energy spectra, time dynamics and correlations of such systems efficiently. It is even expected that certain types of optimization problems with application in logistics, time-scheduling and others could be solved more efficiently with the help of quantum effects.

In our experiments, we use superconducting qubits, which can be manipulated on short time scales with respect to their coherence times within a cryogenic environment. Thanks to the relatively simple and reliable fabrication there exists a clear path towards a scalable architecture to realize the building blocks of a future quantum computer.

Subtopics
Multi-qubit operations
We explore possibilities to efficiently create entanglement between multiple qubits by extending the standard gate set.

The goal is to develop superconducting qubit architectures and control methods to efficiently generate multi-qubit entangled states. One specific direction is to use  couplers connecting multiple superconducting qubits and investigate multi-qubit operations that allow us to entangle and read-out  multiple qubits at the same time.  We will address the question if there is an advantage in using multi-qubit gates over traditional two-qubit gates in practical experiments by assessing the efficiency of such gates in specific algorithms, e.g., for quantum chemistry. Moreover, we investigate different types of qubits and couplers that allow for fast and high-fidelity gate operations. The devices and methods developed here may enhance the scalability of superconducting qubit platforms and the efficiency of quantum algorithms.

Recent projects
Stefan Filipp, Ivan Tsitsilin
Stefan Filipp, Malay Singh
Stefan Filipp, Stefan Filipp, Rudolf Gross, Frank Deppe, Kirill Fedorov, Hans Huebl, Achim Marx, Martin Knudsen, Franz Haslbeck, Leon Koch, Federico Roy, Johannes Schirk, Malay Singh, Ivan Tsitsilin, Max Werninghaus, Johneph Sukham †
Recent publications
M. Ganzhorn, G. Salis, D. J. Egger, A. Fuhrer, M. Mergenthaler, C. Müller, P. Müller, S. Paredes, M. Pechal, M. Werninghaus, and S. Filipp
Research Article | Physical Review Research 2, 033447  (2020)
Quantum Optimal Control
Accurate control over quantum systems at the level of single and multiple qubits is on top of the obvious requirement of long coherence essential for realizing advanced quantum systems and eventually practical quantum computers.

The primary focus of this line of research is on the design, optimal characterization and control of multi-qubit superconducting devices in a circuit QED architecture. We use closed-loop measurements to optimize the tune-up of the system and to obtain high-fidelity quantum gates. Moreover, we address the question how to tailor control and measurements of a complex multi-qubit quantum processor in order to obtain targeted information in the most efficient and robust way. We study experimental techniques to optimize gate operations at the pulse level. Combining these with advanced calibration and characterization methods will allow us to prepare quantum states and run algorithms with high fidelity.

Recent projects
Stefan Filipp, Max Werninghaus, Federico Roy
Stefan Filipp, Stefan Filipp, Rudolf Gross, Frank Deppe, Kirill Fedorov, Hans Huebl, Achim Marx, Martin Knudsen, Franz Haslbeck, Leon Koch, Federico Roy, Johannes Schirk, Malay Singh, Ivan Tsitsilin, Max Werninghaus, Johneph Sukham †
Recent publications
Max Werninghaus and Daniel Egger and Stefan Filipp
Research Article | Physical Review X Quantum 2, 020324  (2021)
Max Werninghaus and Daniel J Egger and Federico Roy and Shai Machnes and Frank K Wilhelm and Stefan Filipp
Research Article | npj Quantum Information 7, 14  (2021)
Quantum Neural Networks
Neural networks based on quantum elements may lead to more efficient ways to realize neural networks. Our research is directed towards building small feed forward neural networks consisting of a few qubits that work in the quantum regime and investigate the question on whether to expect a quantum advantage.

A specific way to realize quantum neuron networks is based on adiabatic ramp quantum neurons. These are implemented via tunable ZZ-type couplings together with an adiabatically varying driving field. Along with higher connectivity brought by multi-qubit couplers we aim to realize first feed-forward networks and explore its capabilities beyond classical approximation.

Recent projects
Stefan Filipp, Franz Haslbeck, Federico Roy
Materials and Fabrication
Improving materials and fabrication concepts is the most essential ingredient for realizing high-quality quantum devices. There can never be enough coherence time.

The quality factor of superconducting quantum circuits is determined both by their design and the quality of the materials and interfaces. We explore different materials including high kinetic inductance superconducting thin films to increase the lifetime of qubits. By modelling the effect of interfaces we design qubits which are less affected by surface residues. We also explore different types of qubits that by design feature long coherence times and high anharmonicity.

Recent projects
Stefan Filipp, Stefan Filipp, Rudolf Gross, Frank Deppe, Kirill Fedorov, Hans Huebl, Achim Marx, Martin Knudsen, Franz Haslbeck, Leon Koch, Federico Roy, Johannes Schirk, Malay Singh, Ivan Tsitsilin, Max Werninghaus, Johneph Sukham †