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Many-body quantum optics with superconducting circuits

The use of superconducting circuits as building blocks for studying light matter interactions at the fundamental level was introduced more than a decade ago and is named Circuit Quantum ElectroDynamics (circuitQED). With this project we want to push these ideas to the next level and build circuits to explore many-body quantum optics.

The key element of these circuits is the Josephson junction, two superconductors separated by a thin insulating barrier. Depending on their size, such junctions can be operated in the quantum regime (size ~ hundreds of nanometers by hundreds of nanometers) or in the classical regime (size ~ several micrometers by several micrometers). In the quantum regime, thanks to their huge non linear inductance they can be used for fabricating quantum two level systems or quantum bits (qubits). In the classical regime, they provide very large and tunable inductances. By making arrays of such classical junctions we can obtain a new type of metamaterials: high impedance and tunable transmission lines.

Transmon and Chain
Artist view of the sample.

In this work we are interested in studying a qubit strongly coupled to such a metamaterial, which contains many electromagnetic degrees of freedom (called plasma modes). By tailoring the properties of this metamaterial (more specifically its characteristic impedance), we can enhance the qubit-plasma modes coupling up to the ultra-strong coupling regime.

We couple the qubit (in red on the figure) via coupling capacitors to an array of 4700 Josephson junctions (in blue). We probe the system via microwave transmission measurements. We obtain a strong hybridization of the qubit levels with several modes of the environment and thus demonstrate an on-chip many-body system.

Related Publications:

Probing a transmon qubit via the ultra-strong coupling to a Josephson waveguide

J. Puertas Martinez, S. Leger, N. Gheereart, R. Dassonneville, L. Planat, F. Foroughi, Y. Krupko, O. Buisson, C. Naud, W. Guichard, S. Florens, I. Snyman, N. Roch,

Arxiv 1802.00633 (2018) Arxiv

Particle production in a waveguide ultra-strongly coupled to a qubit

N. Gheeraert, X. H. H. Zhang, S. Bera, N. Roch, H. U. Baranger and S. Florens,

Physical Review A 98, 043816 (2018), Arxiv | Phys. Rev. A

Stabilizing Spin Coherence Through Environmental Entanglement in Strongly Dissipative Quantum Systems

S. Bera, S. Florens, H. U. Baranger, N. Roch, A. Nazir, and A. W. Chin,

Physical Review B 89, 121108(R) (2014), Arxiv | Phys. Rev. B

Near quantum limited amplifiers

During the last decade, it has been demonstrated that superconducting Josephson circuits behave as quantum bits and are very well suited to realize advanced quantum mechanical experiments. These circuits appear as artificial atoms whose properties are defined by their electronic characteristics (capacitance, inductance and tunnel barrier).

Moreover, given their mesoscopic size, these quantum bits couple very strongly to electromagnetic radiations in the microwave range. Thus, it is now possible to perform quantum optics experiments using microwave photons and to unravel light-matter interactions using circuits. This field is dubbed circuit-QED (Quantum Electro-Dynamics).

Josephson Parametric Amplifier
A near quantum limited Josephson Parametric Amplifier, based on superconducting metamaterials.

Measuring these microwave photons with very high quantum efficiency remains a tremendous challenge, since the energy conveyed by one single microwave photon is hundreds thousand times smaller than the one of usual optical photons. Yet signals at the single-photon level can be measured using Josephson parametric amplifiers.

In our team we are now using superconducting metamaterials (see figure) to engineer the next generation of parametric amplifiers. These new devices allow us to explore the quantum limits of amplification as well as to perform quantum optics experiments.

Related Publications:

Understanding the saturation power of Josephson Parametric Amplifiers made from SQUIDs arrays

L. Planat, R. Dassonneville, J. Puertas Martínez, F. Foroughi, O. Buisson, W. Hasch-Guichard, C. Naud, R. Vijay, K. Murch, and N. Roch,

Arxiv 1809.08476 (2018), Arxiv

Widely tunable, nondegenerate three-wave mixing microwave device operating near the quantum limit

N. Roch, E. Flurin, F. Nguyen, P. Morfin, P. Campagne-Ibarcq, M. Devoret, and B. Huard

Physical Review Letters 108, 147701, (2012), Arxiv | Phys. Rev. Lett.


January 2019

We now have a new PhD graduate: congrats Remy for this very nice defense!

October 2018

Nicolas Gheeraert explained us all about "Quantum non-linearities of a qubit ultra-strongly coupled to a waveguide", his PhD work. Great defense Nicolas!

September 2018

Check our new paper explaining saturation effects in Josephson Parametric Amplifiers.

July 2018

Our paper presenting a detailed analysis of the Kerr non-linearity in a Josephson junctions chain is now available in the Publications section.

June 2018

Javier defended his Phd thesis. Congratulations doctor Puertas Martinez!

February 2018

Check the Publications section. Two new preprints are available.

September 2017

Welcome to Sebastien Leger! He will aim at observing many-body physics effects in superconducting circuits during his PhD.

October 2016

Luca Planat starts his PhD on Josephson Parametric Amplifiers (JPA), welcome Luca!

September 2016

Nicolas Gheeraert is awarded a Raman-Charpak Fellowship to join QuMac, the lab of Vijay, for an internship. Congratulations Nicolas!

September 2016

Pictures of the new lab are available, check the Photo Gallery section.

September 2016

Our review paper on quantum trajectories has just been published.

April 2016

Our paper on "Unexpectedly allowed transitions" in transmon qubits is now out. Have a look at the Publications section.

September 2015

Welcome to Remy Dassonneville who starts his PhD!

June 2015

Wanna know what is a quantum trajectory? Have a look at our new paper on the Arxiv.

April 2015

We are happy to welcome our new Phd student: Javier Puertas Martinez.

March 2015

Check our new paper about a Superconducting Quantum Node for Entanglement and Storage of Microwave Radiation!

January 2015

Our recent work on A V-shape superconducting artificial atom based on two inductively coupled transmons is now on the Arxiv.

March 2014

Our paper on measurement induced entanglement between remote superconducting quantum bits has been accepted for publication in Physical Review Letters and featured as a Viewpoint in Physics!

October 2013

After my post-doc in the quantum nanoelectronics lab at UC Berkeley, I am joining the Neel Institue!