CEA |   |   |   |   |   |   | webmail : intra - extra |  Accès VPN-SSL | Contact | Français

PhD subjects

3 sujets IRAMIS

Dernière mise à jour : 18-12-2018


««

• Mesoscopic physics

 

Hybrid quantum circuits coupling a single spin to a superconducting resonator

SL-DRF-19-0559

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé

Groupe Quantronique

Saclay

Contact :

Denis VION

Starting date : 01-05-2019

Contact :

Denis VION

CEA - DRF/IRAMIS/SPEC/GQ

2 5529

Thesis supervisor :

Denis VION

CEA - DRF/IRAMIS/SPEC/GQ

2 5529

This PhD thesis, in cotutelle with the Institut Quantque of the University of Sherbrooke, aims at detecting a single spin with a superconducting resonator, in two distinct cases: a qubit based on a single electron in a quantum dot on the one hand, and a single NV centre spin in diamond in the second hand.

In the first case, while the spin qubit is currently viewed as a prime candidate for quantum information processing, the currently preferred readout method is destructive. The proposed research project aims at experimentally demonstrating in The Unversity of Sherbrooke a new type of measurement based on the parametric modulation of the longitudinal coupling between a superconducting microwave resonator and the qubit.

In the second case of the NV centre, its purely inductive detection with a low impedance resonator will be developed at CEA-Paris-Saclay university.

Towards hybrid quantum computing: from superconducting circuits to nuclear spins

SL-DRF-19-0529

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé

Groupe Quantronique

Saclay

Contact :

Emmanuel FLURIN

Daniel ESTEVE

Starting date : 01-09-2019

Contact :

Emmanuel FLURIN

CEA - DRF/IRAMIS/SPEC/GQ

0622623862

Thesis supervisor :

Daniel ESTEVE

CEA - DSM/IRAMIS/SPEC/GQ

0169085529

Personal web page : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=eflurin

Laboratory link : http://iramis.cea.fr/spec/GQ/

Quantum information has emerged in past decades as a new pillar of science at the crossroad between quantum physics and information processing. In particular, quantum computation holds great promise for surpassing conventional computing at solving certain class of hard problems such as factoring large integers, searching in an unstructured database, or more realistically classifying sets, or addressing the many body problem in quantum chemistry, complex materials or nuclear physics. Quantum bits are the fundamental carriers of quantum information, and numerous condensed matter system have been shown to host degrees of freedom able to faithfully retain such quantum information, in particular in superconducting electrical oscillators or single crystalline defects in high quality materials. The PhD thesis is part of a long term research project of the Quantronics group that aims at combining precisely these two types of quantum systems in a hybrid structure: impurities trapped in solids would form high fidelity memory elements in superconducting quantum processors.

The goal of the PhD thesis will be first to optimize the coupling between the circuit and a single spin trapped in diamond and second to successfully detect the unique microwave photon generated by the de-excitation of the electron spin. This single photon will be captured by a superconducting qubit of the transmon type, a key element of the superconducting quantum processor, thus laying the foundations for a new quantum processor architecture.

Electron tunneling time and its fluctuations

SL-DRF-19-0504

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé

Groupe Nano-Electronique

Saclay

Contact :

Carles ALTIMIRAS

Patrice ROCHE

Starting date : 01-09-2019

Contact :

Carles ALTIMIRAS

CEA - DRF/IRAMIS/SPEC/GNE

01 69 08 55 29

Thesis supervisor :

Patrice ROCHE

CEA - DRF/IRAMIS/SPEC/GNE

0169087216

Personal web page : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=caltimir

Laboratory link : http://iramis.cea.fr/spec/GNE/

More : https://nanoelectronicsgroup.com/

Challenging our classical intuition, quantum tunneling has fascinated physicists for decades. Very soon after its discovery, it raised the question of how much time do particles spend under the classically forbidden barrier. Despite its simplicity, such a question is ill defined in terms of quantum observables and does not admit a single answer, thus triggering over the past decades a bunch of different definitions corresponding to different (thought) scenarios.



Following a proposal by Büttiker & collaborators [1], we will address this question from the perspective of a well-defined observable: that is, measuring the spectrum of time fluctuations of the number of particles residing within the classically forbidden barrier. The idea is to exploit semiconducting 2D electron gases where electrostatically coupled metallic gates are used to generate the electrostatic potential barrier upon which the electrons are scattered. Moreover, we will equally use them to collect the mirror influence-charges fluctuating in response to the tunneling electrons residing within the electrostatic barrier. Despite its conceptual simplicity, implementing such a scenario is a formidable task since it demands collecting a tiny radiofrequency (RF) signal emitted by a huge output-impedance source in a sub-Kelvin (dilution) refrigerator. We will build upon the group’s expertise in RF design and ultra-low noise measurements in cryogenic environments in order to overcome this challenge, notably implementing recently developed high impedance RF matching circuits [2] allowing us to efficiently collect the signal into a RF detection chain.



In a second step, we will perform similar measurements in experimental conditions where electron-electron interactions strongly modify the transport properties across the barrier. Notably a metal/insulator quantum phase transition is driven by such interactions when a 1D wire is interrupted by an impurity, mimicking Tomonaga-Lutinger liquid dynamics [3]. We wish to investigate this physics from the original perspective of the electron tunneling time, as put forward by a recent theoretical finding [4].



The student will participate to the radiofrequency design of the samples, to their fabrication in a clean-room environment, and to their measurement exploiting low noise measurement techniques both in the near DC and the few GHz range. He will become familiar with sub-Kelvin cryogenic techniques as well.



References:

[1] Pedersen, van Langen, and Büttiker, Phys. Rev. B 57, 1838 (1998)

[2] Rolland et al., https://arxiv.org/abs/1810.06217

[3] Anthore et al., Phys. Rev. X 8, 031075 (2018)

[4] Altimiras, Portier and Joyez, Phys. Rev. X 6, 031002 (2016)

 

Retour en haut