Synchronizing the dynamics of a single NV spin qubit on a parametrically coupled radio-frequency field through microwave dressing

A hybrid spin-oscillator system in parametric interaction is experimentally emulated using a single NV spin qubit immersed in a radio frequency (RF) field and probed with a quasi resonant microwave (MW) field. We report on the MW mediated locking of the NV spin dynamics onto the RF field, appearing when the MW driven Rabi precession frequency approaches the RF frequency and for sufficiently large RF amplitudes. These signatures are analog to a phononic Mollow triplet in the MW rotating frame for the parametric interaction and promise to have impact in spin-dependent force detection strategies

Nano-optomechanical measurement in the photon counting regime

Optically measuring in the photon counting regime is a recurrent challenge in modern physics and a guarantee to develop weakly invasive probes. Here we investigate this idea on a hybrid nano-optomechanical system composed of a nanowire hybridized to a single Nitrogen-Vacancy (NV) defect. The vibrations of the nanoresonator grant a spatial degree of freedom to the quantum emitter and the photon emission event can now vary in space and time. We investigate how the nanomotion is encoded on the detected photon statistics and explore their spatio-temporal correlation properties. This allows a quantitative measurement of the vibrations of the nanomechanical oscillator at unprecedentedly low light intensities in the photon counting regime when less than one photon is detected per oscillation period, where standard detectors are dark-noise-limited. These results have implications for probing weakly interacting nanoresonators, for low temperature experiments and for investigating single moving markers

Tunable Nb superconducting resonators based upon a Ne-FIB-fabricated constriction nanoSQUID

Hybrid superconducting--spin systems offer the potential to combine highly coherent atomic quantum systems with the scalability of superconducting circuits. To fully exploit this potential requires a high quality-factor microwave resonator, tunable in frequency and able to operate at magnetic fields optimal for the spin system. Such magnetic fields typically rule out conventional Al-based Josephson junction devices that have previously been used for tunable high-$Q$ microwave resonators. The larger critical field of niobium (Nb) allows microwave resonators with large field resilience to be fabricated. Here, we demonstrate how constriction-type weak links, patterned in parallel into the central conductor of a Nb coplanar resonator using a neon focused ion beam (FIB), can be used to implement a frequency-tunable resonator. We study transmission through two such devices and show how they realise high quality factor, tunable, field resilient devices which hold promise for future applications coupling to spin systems

Superconducting Nanocircuits for Topologically Protected Qubits

For successful realization of a quantum computer, its building blocks (qubits) should be simultaneously scalable and sufficiently protected from environmental noise. Recently, a novel approach to the protection of superconducting qubits has been proposed. The idea is to prevent errors at the "hardware" level, by building a fault-free (topologically protected) logical qubit from "faulty" physical qubits with properly engineered interactions between them. It has been predicted that the decoupling of a protected logical qubit from local noises would grow exponentially with the number of physical qubits. Here we report on the proof-of-concept experiments with a prototype device which consists of twelve physical qubits made of nanoscale Josephson junctions. We observed that due to properly tuned quantum fluctuations, this qubit is protected against magnetic flux variations well beyond linear order, in agreement with theoretical predictions. These results demonstrate the feasibility of topologically protected superconducting qubits.Comment: 25 pages, 5 figure

Interactions et transport électronique dans le système ErSi2/Si (111) (une étude par microscopie et spectroscopie tunnel à basse température)

Cette thèse porte sur l'étude de phénomènes relatifs au gaz d'électrons bidimensionnel (GE2D) d~ surface constitué d'une monocouche de siliciure d'erbium (ErSb) épitaxiée sur un substrat semiconducteur de silicium. Il est établi que le système ErSb/Si(lll) constitue un véritable métal 2D. Deux aspects afférents à ce matériau ont été étudiés par microscopie et spectroscopie tunnel (STM, STS) à basse température. Tout d'abord des atomes ont été déposés sur une couche continue de siliciure d'erbium afm d'étudier localement l'interaction entre le GE2D et des impuretés. L'étude spectroscopique par STS de ces adsorbats ainsi que celle d'impuretés intrinsèques au siliciure a mis en évidence la présence d'états liés aux sites de certaines impuretés. Un modèle de chimisorption (Grimley-Newns-Anderson) et un modèle de type Friedel permettent de rendre compte qualitativement des résultats obtenus expérimentalement. Dans le contexte général de la caractérisation des propriétés électroniques de surfaces de semiconducteurs nous nous sommes intéressés à l'étude des phénomènes de transport de charges injectées par la pointe STM dans des îlots métalliques 2D de siliciure d'erbium. La modification de paramètres tels que la nature chimique de la surface entre les îlots, le type et le niveau de dopage du silicium, ou la température du substrat, permet d'activer ou (d'inhiber) les canaux de conduction parallèle ou perpendiculaire à la surface. Les différents mécanismes d'évacuation des charges à partir de l'îlot nanométrique sont analysés grâce aux spectres de conductance tunnel, sur une large gamme de conductance.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Suspended NbN superconducting resonator for reducing intrinsic losses

International audienceSuperconducting coplanar waveguide (CPW) microwave resonators are crucial elements in Photon detectors, Quantum-limited parametric amplifiers, Narrow-band filters, Read-out, interconnect in quantum processors and Hybrid devices, connecting solid-state spins with superconducting circuits [1-3]. In the quantum regime, the dominant loss mechanism for high-Q superconducting resonators can be attributed to parasitic two-level systems (TLSs) in the dielectrics. Interface TLSs are common by products of the fabrication process, often introduced by impurities associated with Si surfaces [3]. To reduce intrinsic losses, we employ isotropic deep reactive-ion etching (DRIE) of Si substrate to create suspended NbN superconducting resonators (SSR).In this study, thin films of niobium (Nb) and niobium nitride (NbN) are deposited on Si substrate by a DC magnetron sputtering system. The influence of the N2/Ar gas ratio, the deposition current, the substrate bias potential on the superconducting critical temperature of the films are investigated. Plasma etching of Nb and NbN in a SF6 and Cl2-BCl3 gas plasma is studied using an inductively coupled plasma (icp) reactor. Parametric studies on the effects of total gas flow rate and chamber pressure on the edge angles and etch rates are reported. Finally, the suspended NbN superconducting resonator is fabricated and will be tested. This could be applied to the fabrication of superconducting qubits in integrated circuits, offering a path towards longer qubit coherence times.Reference:[1] Landig et al. Coherent spin–photon coupling using a resonant exchange qubit. Nature 560, 179–184 (2018)[2] Tosi et al. Silicon quantum processor with robust long-distance qubit couplings. Nat Commun 8, 450 (2017)[3] Bruno et al. Reducing intrinsic loss in superconducting resonators by surface treatment and deep etching of silicon substrates, Appl. Phys. Lett. 106, 182601 (2015)[4] Kennedy et al. Tunable Nb Superconducting Resonator Based on a Constriction Nano-SQUID Fabricated with a Ne Focused Ion Beam, Phys. Rev. Applied 11, 014006 (2019)

Radio Frequency Reflectometry of Single-Electron Box Arrays for Nanoscale Voltage Sensing Applications

International audienceSingle-electron tunneling transistors (SETs) and boxes (SEBs) exploit the phenomenon of Coulomb blockade to achieve unprecedented charge sensitivities. Single-electron boxes, however, despite their simplicity compared to SETs, have rarely been used for practical applications. The main reason for that is that unlike a SET where the gate voltage controls conductance between the source and the drain, an SEB is a two terminal device that requires either an integrated SET amplifier or high-frequency probing of its complex admittance by means of radio frequency reflectometry (RFR). The signal to noise ratio (SNR) for a SEB is small, due to its much lower admittance compared to a SET and thus matching networks are required for efficient coupling ofSEBs to an RFR setup. To boost the signal strength by a factor of N (due to a random offset charge) SEBs can be connected in parallel to form arrays sharing common gates and sources. The smaller the size of the SEB, the larger the charging energy of a SEB enabling higher operation temperature, and using devices with a small footprint (1000) can be assembled into an array occupying just a few square microns. We show that it is possible to design SEB arrays that may compete with an SET in terms of sensitivity. In this, we tested SETs using RF reflectometry in a configuration with no DC through path (“DC-decoupled SET” or DCD SET) along with SEBs connected to the same matching network. The experiment shows that the lack of a path for a DC current makes SEBs and DCD SETs highly electrostatic discharge (ESD) tolerant, a very desirable feature for applications. We perform a detailed analysis of experimental data on SEB arrays of various sizes and compare it with simulations to devise several ways for practical applications of SEB arrays and DCD SETs