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Josephson Junction Spectroscopy of Mesoscopic Systems

Project description

A Josephson junction-based spectrometer targets mesoscopic systems

Mesoscopic systems are those that are larger than a few atoms or molecules but smaller than the everyday objects we can see and touch. They serve as an interesting testbed for studying the interface between quantum mechanics and macroscopic systems. Mesoscopic devices, which preserve quantum coherence over lengths larger than the atomic scale, offer a unique opportunity to both engineer and investigate excitations at the single quanta level. However, current spectroscopic methods do not enable one to probe mesoscopic systems with radiation and detect their small absorption signals. The European Research Council-funded JSPEC project will develop an on-chip, Josephson junction-based spectrometer ideally suited for probing elementary excitations in mesoscopic systems.

Objective

Spectroscopy is a powerful tool to probe matter. By measuring the spectrum of elementary excitations, one reveals the symmetries and interactions inherent in a physical system. Mesoscopic devices, which preserve quantum coherence over lengths larger than the atomic scale, offer a unique possibility to both engineer and investigate excitations at the single quanta level. Unfortunately, conventional spectroscopy techniques are inadequate for coupling radiation to mesoscopic systems and detecting their small absorption signals. I propose an on-chip, Josephson-junction based spectrometer which surpasses state-of-the-art instruments and is ideally suited for probing elementary excitations in mesoscopic systems. It has an original design providing uniform wideband coupling from 2-2000 GHz, low background noise, high sensitivity, and narrow linewidth.

I describe the operating principle and design of the spectrometer, show preliminary results demonstrating proof-of-concept, and outline three experiments which exploit the spectrometer to address important issues in condensed matter physics. The experiments are: measuring the lifetime of single quasiparticle and excited Cooper pair states in superconductors, a topic relevant for quantum information processing; determining whether graphene has a bandgap, a fundamental yet unresolved question; and recording a clear spectroscopic signature of Majorana bound states in topological superconductor weak links.

Various applications of the superconducting circuits developed for the spectrometer include a Josephson vector network analyzer, a cryogenic mixer, a THz camera, a detector for radioastronomy, and a scanning microwave impedance microscope. In itself the proposed JJ spectrometer is a general purpose tool that will benefit researchers studying mesoscopic systems. Ultimately, Josephson junction spectroscopy should not only be useful to detect existing elementary excitations but also to discover new ones.

Host institution

COLLEGE DE FRANCE
Net EU contribution
€ 1 651 232,50
Address
PLACE MARCELIN BERTHELOT 11
75005 Paris
France

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Region
Ile-de-France Ile-de-France Paris
Activity type
Higher or Secondary Education Establishments
Links
Total cost
€ 1 997 497,50

Beneficiaries (2)