A5078852469- Quantum and electron transport phenomena
- Quantum Information and Cryptography
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Superconducting and THz Device Technology
- Quantum Computing Algorithms and Architecture
- Mechanical and Optical Resonators
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Electrical Measurement Techniques
- Semiconductor Quantum Structures and Devices
- Surface and Thin Film Phenomena
- Advanced Frequency and Time Standards
- Nonlinear Dynamics and Pattern Formation
- Microwave Engineering and Waveguides
- Radio Frequency Integrated Circuit Design
- Graphene research and applications
- Advanced Thermodynamics and Statistical Mechanics
- Quantum Mechanics and Applications
- Quantum optics and atomic interactions
- Photonic and Optical Devices
- Superconductivity in MgB2 and Alloys
- Optical Network Technologies
- Force Microscopy Techniques and Applications
- Gyrotron and Vacuum Electronics Research
- Strong Light-Matter Interactions
Delft University of Technology
2021-2024
QuTech
2021-2024
Physikalisch-Technische Bundesanstalt
2023-2024
Karlsruhe Institute of Technology
2016-2021
Universidad de Zaragoza
2019
Istituto Nazionale di Fisica Nucleare, Sezione di Roma I
2019
National University of Science and Technology
2016-2019
Johannes Gutenberg University Mainz
2016
National Institute of Standards and Technology
2016
Abstract As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds microseconds, they are currently one the leading platforms for information processing. However, needs further improve by orders magnitude reduce prohibitive hardware overhead current error correction schemes. Reaching this goal hinges on reducing density broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source nonequilibrium...
Andreev bound states are fermionic localized in weak links between superconductors, which can be occupied with spinful quasiparticles. Recently, experiments embedding a nanowire Josephson junction into superconducting circuit have enabled coherent manipulation of single spin. However, these remained limited to small magnetic fields. Here, the authors measure microwave spectra fields up $\ensuremath{\sim}$ 250 mT and identify singlet, doublet, triplet interacting spins.
Superconducting high kinetic inductance elements constitute a valuable resource for quantum circuit design and millimeter-wave detection. Granular aluminum (GrAl) in the superconducting regime is particularly interesting material since it has already shown range of nH$/\Box$ its deposition compatible with conventional Al/AlOx/Al Josephson junction fabrication. We characterize microwave resonators fabricated from GrAl room temperature resistivity $4 \times 10^3\,\mu\Omega\cdot$cm, which...
Out of equilibrium quasiparticles (QPs) are one the main sources decoherence in superconducting quantum circuits and that is particularly detrimental devices with high kinetic inductance, such as impedance resonators, qubits, detectors. Despite significant progress understanding QP dynamics, pinpointing their origin decreasing density remain outstanding tasks. The cyclic process recombination generation QPs implies exchange phonons between thin film underlying substrate. Reducing number...
We realize a hybrid superconductor-semiconductor transmon device in which the Josephson effect is controlled by gate-defined quantum dot an InAs/Al nanowire. Microwave spectroscopy of transmon's transition spectrum allows us to probe ground state parity as function gate voltages, external magnetic flux, and field applied parallel The measured phase diagram agreement with that predicted single-impurity Anderson model superconducting leads. Through continuous time monitoring circuit we...
We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of quantum dot Josephson junction tuned be in spin-1/2 ground state with an unpaired quasiparticle. Because spin-orbit coupling, we resolve two flux-sensitive branches the spectrum, depending on spin A finite magnetic field shifts energy, favoring one and resulting anomalous effect. demonstrate excitation direct spin-flip transition using all-electrical control. Manipulation control enable future...
Josephson junctions in InAs nanowires proximitized with an Al shell can host gate-tunable Andreev bound states. Depending on the state occupation, fermion parity of junction be even or odd. Coherent control states has recently been achieved within each sector, but it is impeded by incoherent switches due to excess quasiparticles superconducting environment. Here, we show that polarize dynamically using microwave pulses embedding a LC resonator. We demonstrate polarization up...
The introduction of crystalline defects or dopants can give rise to so-called "dirty superconductors", characterized by reduced coherence length and quasiparticle mean free path. In particular, granular superconductors such as Granular Aluminum (GrAl), consisting remarkably uniform grains connected Josephson contacts have attracted interest since the sixties thanks their rich phase diagram practical advantages, like increased critical temperature, field, kinetic inductance. Here we report...
Microwave kinetic inductance detectors (MKIDs) are central equipment in radioastronomy, thanks to their ease of fabrication and potential for multiplexing, which allow millimeter-wavelength cameras with thousands pixels. However, increasing obtain maximum responsivity degrades performance, due the onset nonlinearities. This work determines optimum working point MKIDs by taking into account interplay between these two competing factors. It is also found that a lower-gapped ground plane can...
Bloch oscillations in small Josephson junctions were predicted theoretically as the quantum dual to oscillations. A significant consequence of this prediction is emergence quantized current steps, so-called Shapiro when synchronizing an external microwave signal. These steps potentially enable a fundamental standard I, defined via frequency f signal and elementary charge e, I = ± n × 2ef, where natural number. Here, we realize relation by Al/AlO
We present a planar qubit design based on superconducting circuit that we call concentric transmon. While employing straightforward fabrication process using Al evaporation and lift-off lithography, observe lifetimes coherence times in the order of 10 μs. systematically characterize loss channels such as incoherent dielectric loss, Purcell decay radiative losses. The implementation gradiometric SQUID loop allows for fast tuning transition frequency therefore full tomographic control quantum...
We report on a detailed study of the optical response and ${T}_{c}\text{\ensuremath{-}}\ensuremath{\rho}$ phase diagram (${T}_{c}$ being superconducting critical temperature $\ensuremath{\rho}$ normal state resistivity film) granular aluminum, combining transport measurements high resolution spectroscopy technique. The is discussed as resulting from an interplay between stiffness, Coulomb repulsion, gap $\mathrm{\ensuremath{\Delta}}$. provide direct evidence for two different types well...
Determining the state of a qubit on time scale much shorter than its relaxation is an essential requirement for quantum information processing. With aid nondegenerate parametric amplifier, we demonstrate continuous detection jumps transmon with $90\mathrm{%}$ fidelity discrimination. Entirely fabricated by standard two-step optical-lithography techniques, this type amplifier consists dispersion-engineered Josephson-junction (JJ) array. By using long arrays, containing...
Reading out the state of superconducting artificial atoms typically relies on dispersive coupling to a readout resonator. For given system noise temperature, increasing circulating photon number $\bar{n}$ in resonator enables shorter measurement time and is therefore expected reduce errors caused by spontaneous atom transitions. However, generally observed also increase these transition rates. Here we present fluxonium which measure an overall flat dependence rates between its first two...
We report the detection of a gate-tunable kinetic inductance in hybrid InAs/Al nanowire. For this purpose, we have embedded nanowire into quarter-wave coplanar waveguide resonator and measured resonance frequency circuit. find that can be changed via gate voltage controls electron density proximitized semiconductor thus inductance. Applying Mattis-Bardeen theory, extract dependence normal state conductivity nanowire, as well its superconducting gap. Our measurements complement existing...
Quantum error correction will be an essential ingredient in realizing fault-tolerant quantum computing. However, most schemes rely on the assumption that errors are sufficiently uncorrelated space and time. In superconducting qubits, this is drastically violated presence of ionizing radiation, which creates bursts high-energy phonons substrate. These can break Cooper pairs superconductor and, thus, create quasiparticles over large areas, consequently reducing qubit coherence across device a...
We present an experimental investigation of stochastic switching a bistable Josephson junctions array resonator with resonance frequency in the GHz range. As device is regime where anharmonicity on order linewidth, bistability appears for pump strength only few photons. measure dynamics by continuously observing jumps between two metastable states, which occur rate ranging from Hz down to mHz. The strongly depends strength, readout and temperature, following Kramer's law. interplay...
We developed a versatile integrated control and readout instrument for experiments with superconducting quantum bits (qubits), based on field-programmable gate array (FPGA) platform. Using this platform, we perform measurement-based, closed-loop feedback operations $428 \, \mathrm{ns}$ platform latency. The capability is instrumental in realizing active reset initialization of the qubit into ground state time much shorter than its energy relaxation $T_1$. show experimental results...
We analyze the effect of circuit parameter variation on performance Josephson traveling-wave parametric amplifiers (JTWPAs). Specifically, JTWPA concept we investigate is using flux-biased nonhysteretic rf-SQUIDs in a transmission line configuration, which harnesses three-wave mixing (3WM) regime. Dispersion engineering enables phase-matching to achieve power gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math...
We present an argon ion beam milling process to remove the native oxide layer forming on aluminum thin films due their exposure atmosphere in between lithographic steps. Our cleaning is readily integrable with conventional fabrication of Josephson junction quantum circuits. From measurements internal quality factors superconducting microwave resonators and without contacts, we place upper bound residual resistance milled contact 50 mΩ μm2 at a frequency 4.5 GHz. Resonators for which only 6%...
We present scanning tunneling microscope (STM) measurements of the local electronic structure superconducting granular aluminium films. The STM spectra show a homogeneously increased gap compared to that aluminum, both near and above Mott resistivity ${\ensuremath{\rho}}_{\mathrm{M}}\ensuremath{\approx}400\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$. Above ${\ensuremath{\rho}}_{\mathrm{M}}$ we find Coulomb charging effects, first indication electrical...
The high kinetic inductance offered by granular aluminum (grAl) has recently been employed for linear inductors in superconducting high-impedance qubits and detectors. Due to its large critical current density compared typical Josephson junctions, resilience external magnetic fields, low dissipation, grAl may also provide a robust source of non-linearity strongly driven quantum circuits, topological superconductivity, hybrid systems. Having said that, can the be sufficient build qubit? Here...
Fast discrimination between quantum states of superconducting artificial atoms is an important ingredient for information processing. In circuit electrodynamics, increasing the signal-field amplitude in readout resonator, dispersively coupled to atom, improves signal-to-noise ratio and increases measurement strength. Here, we employ this effect over 2 orders magnitude power, made possible by unique combination a dimer-Josephson-junction-array amplifier with large dynamic range fact that our...