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Home > Scientific teams > Electrons Photons Surfaces > Quantum Circuits (QCMX)


by Peretti Jacques - published on , updated on

QCMX Webpage

The goal of the QCMX Lab is to explore the quantum properties of electronic circuits and matter. Our strategy consists in coupling superconducting circuits normally used to process quantum information to materials in order to probe their quantum properties and discover new electronic states of matter. This could make it possible to identify new carriers of quantum information and to simulate complex many-body quantum problems.

Contacts: Landry Bretheau, Joël Griesmar & Jean-Damien Pillet

Find us: Google Maps | Ecole Polytechnique, PMC, Building 83, 1st floor
Offices / Labs: 83.20.18, 83.20.19, 83.20.20, 83.20.25 and 83.20.37


- Landry Bretheau
- Joël Griesmar
- Jean-Damien Pillet

Research Engineer
- Everton Arrighi

- Ambroise Peugeot

PhD Students
- Samy Annabi
- Hannes Riechert
- Solenn Cances:

Regular Visitors
- Danijela Markovic: CNRS Researcher at UmPhy Thales

- Pierre-Eugène Coulon: was a Research Engineer for 1.3 year in 2018-2020
- Interns: Baptiste Carles (2022, ENS Paris-Saclay M1), Etienne Bargel (2020, ENS Paris-Saclay L3), Elie De Seze (2020, ENS Paris-Saclay L3), Luke Pilache (2020, X-Bachelor L2).

We are always looking for highly motivated PhD students or postdocs. Please contact us by email.


- Sep 2022: Welcome to Solenn who joined the group as a PhD Student.
- Sep 2022: Welcome to Joël who joined the group as an Assistant Professor!
- Aug 2022: Goodbye to Joël who just got a permanent position.
- Feb 2022: Joël published a nice popularization article in PMC’s newsletter on how a dilution fridge works.
- Feb 2022: Welcome to Everton who joined the group as a Research Engineer.
- Jan 2022: Hannes built 2 fancy RF sample-holders called JAWS. Thanks Marius and the ENS team.
- Nov 2021: We’ve installed our new BlueFors dilution cryostat, with vector magnet (3/1/1 T) and bottom loader. Base temp = 8 mK !!! Thanks Mathias & Vojko.
- Nov 2021: We’ve just installed our carbon nanotube furnace. Base temp = 1000 °C !
- Nov 2021: We measured our first Rabi oscillations: T1 = 40 µs & T2 = 20 µs. Thanks Manu for the hero qubit.
- Oct 2021: Congrats to Joël & JD for their paper published in Physical Review Research on a high-sensitivity broad-band Josephson junction spectrometer.
- Oct 2021: We’ve received our Quantum Orchestration Platform (OPX) from Quantum Machines. Let’s do real-time control!
- Oct 2021: We performed the spectroscopy of a transmon qubit using our home-made Josephson spectrometer!
- Oct 2021: We measured tunable RF emission from a Josephson junction: 5 MHz bandwidth!
- Oct 2021: Welcome to Hannes & Joël who joined the group as PhD Student and Post-Doctoral Associate.
- Sep 2021: Congrats to Landry who was appointed Professor.
- Sep 2021: New RF equipments from Rohde & Schwarz (2 MSG). New cryogenic circulators and amplifiers from LNF.
- July 2021: Congrats to Ambroise for his paper published in Physical Review X on a dc-Biased Josephson Junction generating two-modes entanglement.
- June 2021: We measured the IV characteristic of a tunnel Josephson junction! DC Josephson effect :)
- May 2021: We joined the PMC Laboratory. What a relief!
- May 2021: Congrats to JD & Landry for their back-to-back papers published in Physical Review Research (013288 & 013289) on Weyl Josephson circuits.
- May 2021: Welcome to Samy who joined the group as a PhD Student.
- Mar 2021: We spotted our first individual carbon nanotube!
- Mar 2021: Landry was interviewed by Polytechnique Insights on the "Plan Quantique"
- Nov 2020: Congrats to Ambroise! He was awarded the 2020 PhOM PhD Award, for his work on "Quantum microwave sources from inelastic Cooper pair tunneling"
- Oct 2020: Welcome to Ambroise who joined the group as a Post-Doctoral associate.
- Sep 2020: We’ve received all the elements to build up our Rayleigh optical characterization platform for the carbon nanotubes (supercontinuum laser, spectrometer, optical table, optics, objectives)
- Sep 2020: Congrats to JD who was awarded a young researcher grant from ANR.
- Sep 2020: Landry was awarded an ERC Starting Grant! → X-News
- July 2020: We measured quantum limited amplification using a SNAIL from Zaki.
- Jun 2020: Congrats to JD for his paper published in SciPost Physics Core on the Scattering description of Andreev molecules.
- Jun 2020: Welcome to Etienne, Elie & Luke who joined the group as summer interns.
- Mar 2020: Congrats to Landry who was awarded the 2020 Nicholas Kurti Science Prize, together with Rebeca Ribeiro from CNRS C2N → X-News
- Feb 2020: Tons of room-T µwave components have arrived.
- Nov 2019: Congrats to JD for his nice PRL, Science, MRS Bulletin & X-News
- Sep 2019: New DC electronic instruments (oscillos, sources, DAC, amp).
- Sep 2019: JD and Landry got tenured!
- Aug 2019: Congrats to JD for his paper published in Nano Letters on Nonlocal Josephson effect in Andreev molecules.
- Aug 2019: New paper by JD & co published in Physical Review Applied on Injection Locking and Parametric Locking in a Superconducting Circuit.
- Jul 2019: We’ve received our cryogenic circulators and amplifiers from LNF.
- Apr 2019: We’ve installed our new BlueFors dilution refregirator. Base temp = 7 mK !!! Thanks Aymeric & Vojko.
- Mar 2019: After 3 months, electricity, masonry and plumbing works are finished! Our lab is ready to get the fridge. And we’ve just received our expresso machine !
- Jan 2019: New RF equipments from Rohde & Schwarz (1 VNA, 1 PSA and 3 MSG).
- Jan 2019: Congrats to Landry for his paper published in Nature Nanotechnology on a graphene-based superconducting qubit → spotlight by Nature Nano & MIT News
- Nov 2018: New paper by Landry & co published in Science that shows gate-controllable superconductivity in monolayer WTe2 → spotlight by MIT News
- Sep 2018: We’ve received a 40L cylinder of He3. Thanks to Michel and the DOE :)
- Sep 2018: New paper by Landry & co in PRB that reports tunneling spectroscopy measurements of graphene proximitized by large-gap superconductors.
- Jul 2018: Congrats to Landry who was awarded a young researcher grant from ANR.
- Dec 2017: The QCMX-lab was awarded a grant from SIRTEQ.
- Sep 2017: We’ve been hired as Assistant Professors (with Startup Grant and Lab Space). Let’s build from scratch a new lab. Long-live QCMX!


The QCMX Lab was created in September 2017 by Landry Bretheau and Jean-Damien Pillet. Since then, we’ve been building up from scratch a brand new laboratory dedicated to the development and measurement of hybrid quantum circuits. This requires access to temperatures close to absolute zero (few mK), nanofabrication tools for the creation of new architectures and electronic instruments in the DC and microwave range for quantum control. The QCMX Lab currently contains two dilution cryostats (from the company BlueFors), which makes it the coldest point of l’X.

One of the crucial ingredients for the operation of quantum circuits is the non-linearity provided by a non-dissipative electronic component called a Josephson junction. These junctions are usually made of two superconductors coupled by tunnel effect through a thin insulating barrier. There is however a wider class of Josephson junctions where superconductors are connected by quantum conductors, such as graphene, semiconductor nanowires or carbon nanotubes. In these systems, barely exploited in the context of quantum circuits, physics is richer because they host additional degrees of freedom associated with the electronic properties of quantum conductors.

We want to use this unexploited resource to design new quantum devices, notably through the development of ultra-clean growth of carbon nanotubes that can be integrated into superconducting circuits. Such Josephson junctions then host elementary electronic excitations in the GHz energy range that can be controlled coherently by means of microwave signals. Our circuits, placed in a microwave cavity to protect it from environmental decoherence, will allow to detect new electronic states of matter such as, for example, Andreev Bound States, Weyl fermions or Majorana fermions.

Hybrid quantum circuit architectures as developed within the QCMX Lab offer tremendous opportunities for quantum simulation, particularly to answer modern questions of fundamental Physics. For example, a charge trapped in a nanotube or a semiconducting nanowire, connected in parallel to a Josephson junction can simulate the problem of a spin 1/2 immersed in a space-dependent magnetic field. In the quantum regime, the degrees of freedom of spin and position are entangled and obey a joined dynamic of great complexity. This experiment would make it possible to understand in more details the spin-boson model which is at the heart of the description of the dissipation in quantum physics.

Beyond this basic situation, it is possible to imagine more complex systems based on networks of several quantum objects. For example, a carbon nanotube connected to multiple superconducting electrodes may behave as a network of quantum dots. Strategies to perform the quantum teleportation of an electron within such electronic device are currently developing.

With the financial support of:
- the Ecole Polytechnique (Young Team Fellowship QCMX)
- the Agence Nationale de la Recherche (Grant ANR-18-CE47-0012 JCJC QIPHSC)
- the DIM SIRTEQ Ile-de-France (Grant ONQC)
- the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 947707)).