QuantERA Call 2019 - 2ème Appel de l'ERA-NET Cofund QuantERA

Superinductor-based Quantum Technologies with Ultrastrong Couplings – SiUCs

Submission summary

Superconducting quantum circuits form one of the most promising solid state platforms for quantum computing. This success builds on the naturally large interaction between light, represented by microwave signals, and matter, embodied by superconducting qubits. Microwave photons are used at every stage of quantum information protocols: qubit manipulation, qubit readout and qubit-qubit coupling. To describe this rich and ubiquitous light-matter interaction, the community has relied so far on the conceptual tools inherited from quantum optics. However, atoms and photons interact weakly, perfectly justifying the use of the rotating wave approximation (RWA), which states that non-resonant processes can be safely neglected. The situation with superconducting circuits is quite different since qubits can literally be wired to transmission lines carrying microwave photons. And limitations of the RWA have already been pointed out for qubit readout or driven-dissipative protocols.
SiUCs will follow a radically new approach: we will harness the potentiality of very large light-matter coupling -often referred to as ultra-strong coupling- instead of fighting it. In order to address this challenging approach in a controlled way, we will develop an architecture based on superinductors. Resonators and transmission lines built from such components display impedances close to the quantum of resistance (R~6.5 kOhms) at gigahertz frequencies, with very low losses, allowing a boost in light-matter interaction.
SiUCS will more specifically focus on improving the efficiency of qubit operations involving light-matter interactions. In addition, superinductors will be used to engineer a missing device of the superconducting quantum circuit toolbox: the microwave single photon detector. Finally, unique many-body physics associated to ultrastrong couplings will be investigated thanks to purposely designed quantum simulators.

SiUCs is defined with a transverse spirit to support several areas of this QuantERA call. The project mainly involves area 4 “Quantum information sciences”. Overall, it provides “novel ideas and applications in quantum science and technologies” with its program to diversify the use of superinductors in superconducting circuits, enhancing light-matter interaction strengths controllably, and exploiting the physics of ultrastrong coupling in the different areas addressed by the project. This project will also “understand and control open quantum systems” using qubits in waveguides. After a first stage focused on enabling technologies, we will be exploring readout improvements in quantum computing technologies with superconducting circuits, the focus of area 3. In addition, larger couplings enable the development of new quantum simulations of condensed matter models. Finally, superinductor technology will be applied to detect microwave photons, an essential missing tool in superconducting quantum information processing. SiUCs is therefore a program providing enabling quantum technologies built from superinductors with direct applicability in quantum computation, quantum simulation and quantum metrology with superconducting circuits.

Project coordination

Pol Forn (Barcelona Supercomputing Center - Centro Nacional de Supercomputación)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


CNR Consiglio Nazionale delle Ricerche
UR Universität Regensburg
SAS Slovak Academy of Science
INEEL Institut Néel
BSC Barcelona Supercomputing Center - Centro Nacional de Supercomputación
KIT Kalsruhe Institut für Technologie

Help of the ANR 300,000 euros
Beginning and duration of the scientific project: March 2020 - 36 Months

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