Multiplying and detecting propagating microwave photons using inelastic Cooper-pair tunneling

The interaction between propagating microwave fields and Cooper-pair tunneling across a DC-voltage-biased Josephson junction can be highly nonlinear. We show theoretically that this nonlinearity can be used to convert an incoming single microwave photon into an outgoing n-photon Fock state in a different mode. In this process, the electrostatic energy released in a Cooper-pair tunneling event is transferred to the outgoing Fock state, providing energy gain. The created multiphoton Fock state is frequency entangled and highly bunched. The conversion can be made reflectionless (impedance matched) so that all incoming photons are converted to n-photon states. With realistic parameters, multiplication ratios n > 2 can be reached. By two consecutive multiplications, the outgoing Fock-state number can get sufficiently large to accurately discriminate it from vacuum with linear postamplification and power measurement. Therefore, this amplification scheme can be used as a single-photon detector without dead time

Development of a Neurotensin-Derived 68Ga-Labeled PET Ligand with High In Vivo Stability for Imaging of NTS1 Receptor-Expressing Tumors

Overexpression of the neurotensin receptor type 1 (NTS1R), a peptide receptor located at the plasma membrane, has been reported for a variety of malignant tumors. Thus, targeting the NTS1R with 18F- or 68Ga-labeled ligands is considered a straightforward approach towards in vivo imaging of NTS1R-expressing tumors via positron emission tomography (PET). The development of suitable peptidic NTS1R PET ligands derived from neurotensin is challenging due to proteolytic degradation. In this study, we prepared a series of NTS1R PET ligands based on the C-terminal fragment of neurotensin (NT(8–13), Arg8-Arg9-Pro10-Tyr11-Ile12-Leu13) by attachment of the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) via an Nω-carbamoylated arginine side chain. Insertion of Ga3+ in the DOTA chelator gave potential PET ligands that were evaluated concerning NTS1R affinity (range of Ki values: 1.2–21 nM) and plasma stability. Four candidates were labeled with 68Ga3+ and used for biodistribution studies in HT-29 tumor-bearing mice. [68Ga]UR-LS130 ([68Ga]56), containing an N-terminal methyl group and a β,β-dimethylated tyrosine instead of Tyr11, showed the highest in vivo stability and afforded a tumor-to-muscle ratio of 16 at 45 min p.i. Likewise, dynamic PET scans enabled a clear tumor visualization. The accumulation of [68Ga]56 in the tumor was NTS1R-mediated, as proven by blocking studies

Quantum bits with Josephson junctions

Already in the first edition of this book (Barone and Paterno, "Fundamentals and Physics and Applications of the Josephson Effect", Wiley 1982), a great number of interesting and important applications for Josephson junctions were discussed. In the decades that have passed since then, several new applications have emerged. This chapter treats one such new class of applications: quantum optics and quantum information processing (QIP) based on superconducting circuits with Josephson junctions. In this chapter, we aim to explain the basics of superconducting quantum circuits with Josephson junctions and demonstrate how these systems open up new prospects, both for QIP and for the study of quantum optics and atomic physics.Comment: 30 pages, 10 figures. Book chapter for a new edition of Barone and Paterno's "Fundamentals and Physics and Applications of the Josephson Effect". Final versio

Blocage de Coulomb dans les transistors silicium à base de nanofils

We present electrical transport measurements at low temperature on single-electron transistors (SETs) based on silicon nanowire MOSFETs.The Coulomb island is formed in the wire not by constrictions or oxide barriers but by a modulation of the doping level and a gate electrode covering the central part of the wire. The devices form very stable SETs with well-controlled properties.When few electrons are on the island, it is in a localized regime with strong fluctuations of the spacing between Coulomb blockade peaks. When more than a few tens of electrons are on the island it becomes diffusive. Then the fluctuations of the peak spacing are small and scale with the single-particle level spacing.The well-controlled Coulomb blockade allows to investigate the barriers formed by the low-doped parts of the wire. On a small scale, the charging of single dopants in the barriers causes anomalies in the Coulomb blockade spectrum which allow to determine capacitance matrix, approximate position, dynamics and spin of the individual dopants. On a large scale, the increase of the electron density in the barriers with gate voltage leads to a dramatic increase of the dielectric constant in the barriers. We find dielectric constant and conductance of the barriers to be linked as predicted by scaling laws describing the metal-insulator transition.Cette thèse est consacrée à des mesures de transport électronique dans des transistors mono-électroniques de type MOSFET silicium à base de nanofil.L'îlot de blocage de Coulomb n'est pas formé par des constrictions ou des barrières d'oxyde mais par une modulation du dopage et une grille couvrant la partie centrale du fil. Ces dispositifs sont des transistors mono-électroniques très stables et bien contrôlés.Quand il ne contient que peu d'électrons, l'îlot est dans un régime localisé où l'espacement entre résonances de Coulomb est très irrégulier. A partir de quelques dizaines d'électrons l'îlot devient diffusif. Dans ce cas les fluctuations de l'espacement entre résonances sont petites et correspondent à l'espacement entre niveaux à une particule.Le blocage de Coulomb contrôlé permet d'analyser les barrières formées par les parties faiblement dopées du fil. A petite échelle, le remplissage de dopants individuels cause des anomalies dans le spectre de Coulomb qui permettent de remonter à la matrice de capacité, la position approximative, la dynamique et le spin des dopants. A grande échelle l'augmentation de la densité électronique dans les barrières avec la tension de grille entraîne une forte augmentation de la constante diélectrique dans les barrières. Nous observons un bon accord entre constante diélectrique et conductance des barrières via les lois d'échelle de la transition métal-isolant

Blocage de Coulomb dans les transistors silicium à base de nanofils

We present electrical transport measurements at low temperature on single-electron transistors (SETs) based on silicon nanowire MOSFETs.The Coulomb island is formed in the wire not by constrictions or oxide barriers but by a modulation of the doping level and a gate electrode covering the central part of the wire. The devices form very stable SETs with well-controlled properties.When few electrons are on the island, it is in a localized regime with strong fluctuations of the spacing between Coulomb blockade peaks. When more than a few tens of electrons are on the island it becomes diffusive. Then the fluctuations of the peak spacing are small and scale with the single-particle level spacing.The well-controlled Coulomb blockade allows to investigate the barriers formed by the low-doped parts of the wire. On a small scale, the charging of single dopants in the barriers causes anomalies in the Coulomb blockade spectrum which allow to determine capacitance matrix, approximate position, dynamics and spin of the individual dopants. On a large scale, the increase of the electron density in the barriers with gate voltage leads to a dramatic increase of the dielectric constant in the barriers. We find dielectric constant and conductance of the barriers to be linked as predicted by scaling laws describing the metal-insulator transition.Cette thèse est consacrée à des mesures de transport électronique dans des transistors mono-électroniques de type MOSFET silicium à base de nanofil.L'îlot de blocage de Coulomb n'est pas formé par des constrictions ou des barrières d'oxyde mais par une modulation du dopage et une grille couvrant la partie centrale du fil. Ces dispositifs sont des transistors mono-électroniques très stables et bien contrôlés.Quand il ne contient que peu d'électrons, l'îlot est dans un régime localisé où l'espacement entre résonances de Coulomb est très irrégulier. A partir de quelques dizaines d'électrons l'îlot devient diffusif. Dans ce cas les fluctuations de l'espacement entre résonances sont petites et correspondent à l'espacement entre niveaux à une particule.Le blocage de Coulomb contrôlé permet d'analyser les barrières formées par les parties faiblement dopées du fil. A petite échelle, le remplissage de dopants individuels cause des anomalies dans le spectre de Coulomb qui permettent de remonter à la matrice de capacité, la position approximative, la dynamique et le spin des dopants. A grande échelle l'augmentation de la densité électronique dans les barrières avec la tension de grille entraîne une forte augmentation de la constante diélectrique dans les barrières. Nous observons un bon accord entre constante diélectrique et conductance des barrières via les lois d'échelle de la transition métal-isolant

Blocage de Coulomb dans les transistors silicium à base de nanofils

Cette thèse est consacrée à des mesures de transport électronique dans des transistors mono-électroniques de type MOSFET silicium à base de nanofil. L'îlot de blocage de Coulomb n'est pas formé par des constrictions ou des barrières d'oxyde mais par une modulation du dopage et une grille couvrant la partie centrale du fil. Ces dispositifs sont des transistors mono-électroniques très stables et bien contrôlés. Quand il ne contient que peu d'électrons, l'îlot est dans un régime localisé où l'espacement entre résonances de Coulomb est très irrégulier. A partir de quelques dizaines d'électrons l'îlot devient diffusif. Dans ce cas les fluctuations de l'espacement entre résonances sont petites et correspondent à l'espacement entre niveaux à une particule. Le blocage de Coulomb contrôlé permet d'analyser les barrières formées par les parties faiblement dopées du fil. A petite échelle, le remplissage de dopants individuels cause des anomalies dans le spectre de Coulomb qui permettent de remonter à la matrice de capacité, la position approximative, la dynamique et le spin des dopants. A grande échelle l'augmentation de la densité électronique dans les barrières avec la tension de grille entraîne une forte augmentation de la constante diélectrique dans les barrières. Nous observons un bon accord entre constante diélectrique et conductance des barrières via les lois d'échelle de la transition métal-isolant.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Foreword

International audienc

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)

Absorptive filters for quantum circuits: Efficient fabrication and cryogenic power handling

We present an efficient fabrication method for absorptive microwave filters based on Eccosorb CR-124. Filters are fabricated from readily available parts, and their cutoff frequency can be set by their length. They exhibit desirable properties such as a very large and deep stop band with rejection beyond 120 dB at least up to 40 GHz, more than 10 dB return loss in both the pass and the stop band, and an error-function shaped step response without overshoot. Measurements at very low temperatures show that the filters thermalize on a time scale of approximately 100 s, and that they can absorb power as high as 100 nW with their noise temperature staying remarkably low, below 100 mK. These properties make the filters ideal for cryogenic filtering and filtering of intermediate frequency port signals of mixers