arXiv subjects

Julien Basset

Publications and source records attributed to Julien Basset.

17 recordsLinked to original sources

arXiv2025

Fast and Continuous Detection of Single Microwave Photons via Photo-assisted Quasiparticle Tunneling to a Superconducting Island

We demonstrate a single-photon detector operating in the microwave domain, based on photo-assisted quasiparticle tunneling events that poison a superconducting island. The detection relies on continuously monitoring the island's charge parity using microwave reflectometry. This scheme achieves 10\% detection efficiency with sub \SI{50}{\ns} time resolution and short dead time ($\sim \SI{1}{\us}$), for microwave photons at \SI{10}{\GHz}. The detector features three junctions connected to a superconducting island, which together carry out photoelectric conversion and charge readout. The enhanced light--matter coupling, crucial to photon to quasiparticle conversion, is provided by a granular aluminum-based high-impedance microwave resonator. The time resolved detection of itinerant microwave photon opens up new perspectives in quantum sensing, microwave quantum optics and mesoscopic physics.

cond-mat.mes-hall↗

arXiv2023

Efficient Microwave Photon to Electron Conversion in a High Impedance Quantum Circuit

We demonstrate an efficient and continuous microwave photon to electron converter with large quantum efficiency ($83\%$) and low dark current. These unique properties are enabled by the use of a high kinetic inductance disordered superconductor, granular aluminium, to enhance light-matter interaction and the coupling of microwave photons to electron tunneling processes. As a consequence of strong coupling, we observe both linear and non-linear photon-assisted processes where 2, 3 and 4 photons are converted into a single electron at unprecedentedly low light intensities. Theoretical predictions, which require quantization of the photonic field within a quantum master equation framework, reproduce well the experimental data. This experimental advancement brings the foundation for high-efficiency detection of individual microwave photons using charge-based detection techniques.

quant-ph↗

arXiv2023

Imaging the Quantum Capacitance of Strained MoS2 Monolayers by Electrostatic Force Microscopy

We implemented radio frequency-assisted electrostatic force microscopy (RF-EFM) to investigate the electric field response of biaxially strained molybdenum disulfide (MoS2) monolayers (MLs) in the form of mesoscopic bubbles, produced via hydrogen (H)-ion irradiation of the bulk crystal. MoS2 ML, a semiconducting transition metal dichalcogenide, has recently attracted significant attention due to its promising optoelectronic properties, further tunable by strain. Here, we take advantage of the RF excitation to distinguish the intrinsic quantum capacitance of the strained ML from that due to atomic scale defects, presumably sulfur vacancies or H-passivated sulfur vacancies. In fact, at frequencies fRF larger than the inverse defect trapping time, the defect contribution to the total capacitance and to transport is negligible. Using RF-EFM at fRF = 300 MHz, we visualize simultaneously the bubble topography and its quantum capacitance. Our finite-frequency capacitance imaging technique is non-invasive and nanoscale, and can contribute to the investigation of time and spatial-dependent phenomena, such as the electron compressibility in quantum materials, which are difficult to measure by other methods.

cond-mat.mes-hall↗

arXiv2022

Quantum bath engineering of a high impedance microwave mode through quasiparticle tunneling

We demonstrate a new approach to dissipation engineering in microwave quantum optics. For a single mode, dissipation usually corresponds to quantum jumps, where photons are lost one by one. Here, we are able to tune the minimal number of lost photons per jump to be two (or more) with a simple dc voltage. As a consequence, different quantum states experience different dissipation. Causality implies that the states must also experience different energy shifts. Our measurements of these Lamb shifts are in good agreement with the predictions of the Kramers-Kronig relations for single quantum states in a regime of highly non-linear bath coupling. This work opens new possibilities for quantum state manipulation in circuit QED, without relying on the Josephson effect.

quant-ph↗

arXiv2021

Gate-Assisted Phase Fluctuations in All-Metallic Josephson Junctions

The discovery that a gate electrode suppresses the supercurrent in purely metallic systems is missing a complete physical understanding of the mechanisms at play. We here study the origin of this reduction in a Superconductor-Normal metal-Superconductor Josephson junction by performing, on the same device, a detailed investigation of the gate-dependent switching probability together with the local tunnelling spectroscopy of the normal metal. We demonstrate that high energy electrons leaking from the gate trigger the reduction of the critical current which is accompanied by an important broadening of the switching histograms. The switching rates are well described by an activation formula including an additional term accounting for the injection of rare high energy electrons from the gate. The rate of electrons obtained from the fit remarkably coincides with the independently measured leakage current. Concomitantly, a negligible elevation of the local temperature is found by tunnelling spectroscopy which excludes overheating scenarios.

cond-mat.supr-con↗

arXiv2019

Nonadiabatic Dynamics of Strongly Driven Diffusive Josephson Junctions

By measuring the Josephson emission of a diffusive Superconductor-Normal metal-Superconductor (SNS) junction at a finite temperature we reveal a non-trivial sensitivity of the supercurrent to microwave irradiation. We demonstrate that the harmonic content of the current-phase relation is modified due to the energy redistribution of quasiparticles in the normal wire induced by the electromagnetic field. The distortion originates from the phase-dependent out-of-equilibrium distribution function which is strongly affected by the ac-response of the spectral supercurrent. For phases close to $π$, transitions accross the Andreev gap are dynamically favored leading to a supercurrent reduction. This finding is supported by a comparison with the quasiclassical Green's function theory of superconductivity in diffusive SNS junctions under microwave irradiation.

cond-mat.mes-hall↗

arXiv2019

Quantum noise in carbon nanotubes as a probe of correlations in the Kondo regime

Most of the time, electronic excitations in mesoscopic conductors are well described, around equilibrium, by non-interacting Landau quasi-particles. This allows a good understanding of the transport properties in the linear regime. However, the role of interaction in the non-equilibrium properties beyond this regime has still to be established. A paradigmatic example is the Kondo many body state, which can be realized in a carbon nanotube (CNT) quantum dot for temperatures below the Kondo temperature $T_K$. As CNT possess spin and orbital quantum numbers, it is possible to investigate the twofold degenerate SU(2) Kondo effect as well as the four fold degenerate SU(4) state by tuning the degeneracies and filling factor. This article aims at providing a comprehensive review on our recent works on the Kondo correlations probed by quantum noise measurement both at low and high frequencies and demonstrate how current noise measurements yield new insight on interaction effects and dynamics of a Kondo correlated state.

cond-mat.mes-hall↗

arXiv2019

High Kinetic Inductance Microwave Resonators Made by He-Beam Assisted Deposition of Tungsten Nanowires

We evaluate the performance of hybrid microwave resonators made by combining sputtered Nb thin films with Tungsten nanowires grown with a He-beam induced deposition technique. Depending on growth conditions the nanowires have a typical width $w\in[35-75]$~nm and thickness $t\in[5-40]$~nm. We observe a high normal state resistance $R_{sq}\in [65-150]$ $Ω/sq$ which together with a critical temperature $T_c\in[4-6]~K$ ensure a high kinetic inductance making the resonator strongly nonlinear. Both lumped and coplanar waveguide resonators were fabricated and measured at low temperature exhibiting internal quality factors up to $3990$ at $4.5$~GHz in the few photon regime. Analyzing the wire length, temperature and microwave power dependence we extracted a kinetic inductance for the W nanowire of $L_K\approx15$ pH/sq, which is 250 times higher than the geometrical inductance, and a Kerr non-linearity as high as $K_{W,He}/2π=200 \pm 120$~Hz/photon at $4.5$~GHz. The nanowires made with the helium focused ion beam are thus versatile objects to engineer compact, high impedance, superconducting environments with a mask and resist free direct write process.

cond-mat.mes-hall↗

arXiv2016

Heat dissipation and fluctuations in a driven quantum dot

While thermodynamics is a useful tool to describe the driving of large systems close to equilibrium, fluctuations dominate the distribution of heat and work in small systems and far from equilibrium. We study the heat generated by driving a small system and change the drive parameters to analyse the transition from a drive leaving the system close to equilibrium to driving it far from equilibrium. Our system is a quantum dot in a GaAs/AlGaAs heterostructure hosting a two-dimensional electron gas. The dot is tunnel-coupled to one part of the two-dimensional electron gas acting as a heat and particle reservoir. We use standard rate equations to model the driven dot-reservoir system and find excellent agreement with the experiment. Additionally, we quantify the fluctuations by experimentally test the theoretical concept of the arrow of time, predicting our ability to distinguish whether a process goes in the forward or backward drive direction.

cond-mat.mes-hall↗

arXiv2016

Measuring the degeneracy of discrete energy levels using a GaAs/AlGaAs quantum dot

We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance, and the ability to perform precise and efficient measurements of energy-dependent tunnelling-in and -out rates from a reservoir. The method is realized using a GaAs/AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunnelling with a precision enhanced by a feedback-control. It is thoroughly tested by tuning orbital and spin-degeneracies with electric and magnetic fields. The technique also lends itself for studying the connection between the ground state degeneracy and the lifetime of the excited states.

cond-mat.mes-hall↗

arXiv2015

Equilibrium free energy measurement of a confined electron driven out of equilibrium

We study out-of equilibrium properties of a quantum dot in a GaAs/AlGaAs two-dimensional electron gas. By means of single electron counting experiments, we measure the distribution of work and dissipated heat of the driven quantum dot and relate these quantities to the equilibrium free energy change, as it has been proposed by C. Jarzynski [Phys. Rev. Lett. {\bf78}, 2690 (1997)]. We discuss the influence of the degeneracy of the quantized energy state on the free energy change as well as its relation to the tunnel rates between the dot and the reservoir.

cond-mat.mes-hall↗

arXiv2014

Spectroscopy of Equilibrium and Non-Equilibrium Charge Transfer in Semiconductor Quantum Structures

We investigate equilibrium and non-equilibrium charge-transfer processes by performing high-resolution transport spectroscopy. Using electrostatically defined quantum dots for energy-selective emission and detection, we achieved unprecedented spectral resolution and a high degree of tunability of relevant experimental parameters. Most importantly, we observe that the spectral width of elastically transferred electrons can be substantially smaller than the linewidth of a thermally broadened Coulomb peak. This finding indicates that the charge-transfer process is fast compared to the electron--phonon interaction time. By drawing an analogy to double quantum dots, we argue that the spectral width of the elastic resonance is determined by the lifetime broadening $h\itΓ$ of the emitter and detector states. Good agreement with the model is found also in an experiment in which the charge transfer is in the regime $h\itΓ\gg k_{\rm{B}}T$. By performing spectroscopy below the Fermi energy, we furthermore observe elastic and inelastic transfer of holes.

cond-mat.mes-hall↗

arXiv2014

Evaluating charge noise acting on semiconductor quantum dots in the circuit quantum electrodynamics architecture

We evaluate the charge noise acting on a GaAs/GaAlAs based semiconductor double quantum dot dipole-coupled to the voltage oscillations of a superconducting transmission line resonator. The in-phase ($I$) and the quadrature ($Q$) components of the microwave tone transmitted through the resonator are sensitive to charging events in the surrounding environment of the double dot with an optimum sensitivity of $8.5\times10^{-5} \mbox{e}/\sqrt{\mbox{Hz}}$. A low frequency $1/f$ type noise spectrum combined with a white noise level of $6.6\times10^{-6}$ $\mbox{e}^2/\mbox{Hz}$ above $1$ Hz is extracted, consistent with previous results obtained with quantum point contact charge detectors on similar heterostructures. The slope of the $1/f$ noise allows to extract a lower bound for the double-dot charge qubit dephasing rate which we compare to the one extracted from a Jaynes-Cummings Hamiltonian approach. The two rates are found to be similar emphasizing that charge noise is the main source of dephasing in our system.

cond-mat.mes-hall↗

arXiv2013

Single-electron Double Quantum Dot Dipole-coupled to a Single Photonic Mode

We have realized a hybrid solid-state quantum device in which a single-electron semiconductor double quantum dot is dipole coupled to a superconducting microwave frequency transmission line resonator. The dipolar interaction between the two entities manifests itself via dispersive and dissipative effects observed as frequency shifts and linewidth broadenings of the photonic mode respectively. A Jaynes-Cummings Hamiltonian master equation calculation is used to model the combined system response and allows for determining both the coherence properties of the double quantum dot and its interdot tunnel coupling with high accuracy. The value and uncertainty of the tunnel coupling extracted from the microwave read-out technique are compared to a standard quantum point contact charge detection analysis. The two techniques are found to be consistent with a superior precision for the microwave experiment when tunneling rates approach the resonator eigenfrequency. Decoherence properties of the double dot are further investigated as a function of the number of electrons inside the dots. They are found to be similar in the single-electron and many-electron regimes suggesting that the density of the confinement energy spectrum plays a minor role in the decoherence rate of the system under investigation.

cond-mat.mes-hall↗

arXiv2012

High Frequency Quantum Admittance and Noise Measurement with an On-chip Resonant Circuit

By coupling a quantum detector, a superconductor-insulator-superconductor junction, to a Josephson junction \textit{via} a resonant circuit we probe the high frequency properties, namely the ac complex admittance and the current fluctuations of the Josephson junction at the resonant frequencies. The admittance components show frequency dependent singularities related to the superconducting density of state while the noise exhibits a strong frequency dependence, consistent with theoretical predictions. The circuit also allows to probe separately the emission and absorption noise in the quantum regime of the superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations, whereas at higher temperature emission noise is also present.

cond-mat.mes-hall↗

arXiv2012

Quantum Noise Measurement of a Carbon Nanotube Quantum Dot in the Kondo Regime

The current emission noise of a carbon nanotube quantum dot in the Kondo regime is measured at frequencies $ν$ of the order or higher than the frequency associated with the Kondo effect $k_B T_K/h$, with $T_K$ the Kondo temperature. The carbon nanotube is coupled via an on-chip resonant circuit to a quantum noise detector, a superconductor-insulator-superconductor junction. We find for $h ν\approx k_B T_K$ a Kondo effect related singularity at a voltage bias $eV \approx h ν$, and a strong reduction of this singularity for $h ν\approx 3 k_B T_K$, in good agreement with theory. Our experiment constitutes a new original tool for the investigation of the non-equilibrium dynamics of many-body phenomena in nanoscale devices.

cond-mat.mes-hall↗

arXiv2010

Emission and Absorption quantum noise measurement with an on-chip resonant circuit

Using a quantum detector, a superconductor-insulator-superconductor junction, we probe separately the emission and absorption noise in the quantum regime of a superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations whereas at higher temperature emission noise is also present. By coupling a Josephson junction, biased above the superconducting gap, to the same resonant circuit, we directly measure the noise power of quasiparticles tunneling through the junction at two resonance frequencies. It exhibits a strong frequency dependence, consistent with theoretical predictions.

cond-mat.mes-hall↗