A5005874844- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Quantum Information and Cryptography
- Surface and Thin Film Phenomena
- Molecular Junctions and Nanostructures
- Quantum Computing Algorithms and Architecture
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Thermodynamics and Statistical Mechanics
- Magnetic properties of thin films
- stochastic dynamics and bifurcation
- Force Microscopy Techniques and Applications
- Quantum optics and atomic interactions
- Semiconductor Quantum Structures and Devices
- Advancements in Semiconductor Devices and Circuit Design
- Mechanical and Optical Resonators
- Topological Materials and Phenomena
- Graphene research and applications
- Semiconductor materials and devices
- Atomic and Subatomic Physics Research
- Quantum Mechanics and Applications
- Superconducting and THz Device Technology
- Radio Frequency Integrated Circuit Design
- Photonic and Optical Devices
- Boron and Carbon Nanomaterials Research
- Crystallography and Radiation Phenomena
CEA Paris-Saclay
2013-2023
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2013-2023
Centre National de la Recherche Scientifique
2013-2023
Service de Physique de l'État Condensé
2006-2023
Institut Rayonnement-Matière de Saclay
2011-2022
Université Paris-Saclay
2018-2022
DSM (Netherlands)
2003-2022
Université Paris-Sud
2011
Laboratoire de physique des Solides
2011
Universidad Autónoma de Madrid
2004
We have designed and operated a superconducting tunnel junction circuit that behaves as two-level atom: the "quantronium." An arbitrary evolution of its quantum state can be programmed with series microwave pulses, projective measurement performed by pulsed readout subcircuit. The measured quality factor coherence Qphi approximately 25,000 is sufficiently high solid-state processor based on this type envisioned.
Decoherence in quantum bit circuits is presently a major limitation to their use for computing purposes. We present experiments, inspired from NMR, that characterise decoherence particular superconducting circuit, the quantronium. introduce general framework analysis of decoherence, based on spectral densities noise sources coupled qubit. Analysis our measurements within this indicates simple model acting discuss various methods fight decoherence.
A metallic electrode connected to electron reservoirs by tunnel junctions has a series of charge states corresponding the number excess electrons in electrode. In contrast with state an atomic or molecular ion, such "island" involve macroscopic conduction island. Island bear some resemblance photon cavity QED, phase conjugate being analogous field cavity. For normal island, decay irreversibly into lower energies. However, ground superconducting island can be coherent superposition differing...
We have determined the individual transmission coefficients of Al quantum point contacts containing up to six conduction channels. The determination is based on a comparison highly nonlinear current-voltage characteristics in superconducting state with predictions theory for single channel contact. find that at least two channels contribute transport even conductance lower than quantum.
Coherent control of quantum states has been demonstrated in a variety superconducting devices. In all these devices, the variables that are manipulated collective electromagnetic degrees freedom: charge, phase, or flux. Here, we demonstrate coherent manipulation system based on Andreev bound states, which microscopic quasiparticle inherent to weak links. Using circuit electrodynamics setup perform single-shot readout this "Andreev qubit". We determine its excited state lifetime and coherence...
Metallic point contacts and tunnel junctions with a small adjustable number of conduction channels have been obtained in the last few years using scanning tunneling microscope break junction techniques. For conventional junctions, reported drift interelectrode spacing regime is typically order 0.5 pm/min (1 pm=10−12 m). We nanofabricated which display smaller than 0.2 pm/h. The improvement results from scaling down by two orders magnitude device dimensions. describe nanofabrication process,...
We have measured the difference between free energies of an isolated superconducting electrode with odd and even number electrons using a Coulomb blockade electrometer. The decrease this energy increasing temperature is in good agreement theoretical predictions assuming BCS density quasiparticle states, except at lowest temperatures where results indicate presence extra level inside gap.
We have measured the supercurrent branch of a superconducting single electron transistor as function gate charge, temperature, and magnetic field. At low temperature field, switching current goes from minimum to maximum when charge is varied 0 e, expected for an island in ground state with even number. When odd number becomes populated by increase or Josephson tunneling strongly suppressed, agreement theoretical predictions.
Using a dual-mode STM-AFM microscope operating below 50 mK we measured the local density of states along small normal wires connected at both ends to superconductors with different phases. We observe that uniform minigap can develop in whole wire and near interfaces. The depends periodically on phase difference. quasiclassical theory superconductivity applied simplified 1D model geometry accounts well for data.
We explore the photonic (bright) side of dynamical Coulomb blockade (DCB) by measuring radiation emitted a dc voltage-biased Josephson junction embedded in microwave resonator. In this regime Cooper pair tunneling is inelastic and associated with transfer an energy $2eV$ into resonator modes. have measured simultaneously current photon emission rate at resonance frequency Our results show two regimes, which each emits either one or photons The spectral properties are accounted for extension...
We performed tunneling spectroscopy of a carbon nanotube quantum dot (QD) coupled to metallic reservoir either in the normal or superconducting state. explore how Kondo resonance, observed when QD's occupancy is odd and normal, evolves towards Andreev bound states (ABS) Within this regime, ABS spectrum consistent with phase transition from singlet degenerate magnetic doublet ground state, quantitative agreement single-level Anderson model leads.
Coherent superpositions of quantum states have already been demonstrated in different superconducting circuits based on Josephson junctions. These are now considered for implementing bits. We report experiments which the state a qubit circuit, quantronium, is efficiently manipulated using methods inspired from nuclear magnetic resonance (NMR): multipulse sequences used to perform arbitrary operations, improve their accuracy, and fight decoherence.
We observe the suppression of finite frequency shot-noise produced by a voltage biased tunnel junction due to its interaction with single electromagnetic mode high impedance. The is embedded in quarter wavelength resonator containing dense SQUID array providing it characteristic impedance kOhms range and resonant tunable 4-6 GHz range. Such gives rise sizeable Coulomb blockade on (roughly 30% reduction differential conductance) allows an efficient measurement spectral density current...
Experiments show that, contrary to long-held predictions, a Josephson junction in series with large enough resistance does not become insulating at low temperature, thus forcing reanalysis of quantum phase transitions these and similar systems.
We show experimentally that a dc biased Josephson junction in series with high-enough-impedance microwave resonator emits antibunched photons. Our is made of simple microfabricated spiral coil resonates at 4.4 GHz and reaches $1.97\text{ }\text{ }\mathrm{k}\mathrm{\ensuremath{\Omega}}$ characteristic impedance. The second order correlation function the power leaking out drops down to 0.3 zero delay, which demonstrates antibunching photons emitted by circuit rate...
We have investigated the suppression of single-electron charging effects in metallic transistors when conductance tunnel junctions becomes larger than quantum ${e}^{2}/h$. find that Coulomb blockade is progressively shifted at lower temperatures. The experimental results agree quantitatively with available $1/T$ expansion high temperature, and qualitatively predictions an effective two-state model low which predicts $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ a for all gate voltages.
An unshunted Josephson tunnel junction switching out of its zero-voltage state is a model system for thermal activation metastable state. For small-capacitance low-critical-current junctions, this process follows generalized Arrhenius law involving dissipation directly in exponent. This escape over barrier can be computed exactly connected to $\mathrm{RC}$ impedance providing large damping. The diffusion branch and the histograms measured such are agreement with theory.
In experiments on single electron devices, the electromagnetic noise from parts of apparatus at temperatures higher than that device can dramatically increase tunnel rates out Coulomb-blocked state and therefore error rate. The electrical lines must be filtered adequately. We derive simple expressions for calculating required attenuation coefficient. describe a wide-band miniature dissipative filter functioning cryogenic temperatures. effective thermalization an experiment 30 mK obtained by...
We have measured the supercurrent flowing through a nonhysteretic, ultrasmall, voltage-biased Josephson junction. In contrast with experiments performed so far on hysteretic junctions, we find peak whose maximum I(s max) increases as temperature T decreases. The asymptotic = 0 value of agrees junction Ambegaokar-Baratoff critical current, predicted by theory.
A general nonlinear response theory is derived for an arbitrary time-dependent Hamiltonian, not necessarily obeying time-reversal symmetry. We consider the application of this to a multiterminal mesoscopic system with interactions and voltages. This allows us obtain generalized Kubo-type formula. derive microscopic expression finite frequency differential conductance matrix, which preserves current conservation gauge invariance. exploit result show that asymmetric part fluctuation matrix at...
We show that a properly dc-biased Josephson junction in series with two microwave resonators of different frequencies emits photon pairs the resonators. By measuring auto- and intercorrelations power leaking out resonators, we demonstrate two-mode amplitude squeezing below classical limit. This nonclassical light emission is found to be quantitative agreement our theoretical predictions, up an rate 2 billion per second.
We derive fluctuation-dissipation relations for a tunnel junction driven through resonator displaying strong quantum fluctuations. find that the derived classical external drives hold, provided effect of circuit's fluctuations is incorporated into modified nonlinear current voltage characteristics. also demonstrate all quantities measured under time dependent bias can be reconstructed from their values dc using photoassisted tunneling relations. confirm these predictions by implementing...
We show experimentally that a dc-biased Josephson junction in series with two microwave resonators emits entangled beams of microwaves leaking out the resonators. In absence stationary phase reference for characterizing entanglement outgoing beams, we measure second-order coherence functions to prove entanglement. The experimental results are found quantitative agreement theory, proving low-frequency noise dc bias is main limitation time beams. This allows us evaluate entropy resonators,...