A5031076318- Quantum and electron transport phenomena
- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Semiconductor Quantum Structures and Devices
- Advancements in Semiconductor Devices and Circuit Design
- Surface and Thin Film Phenomena
- Topological Materials and Phenomena
- Photonic and Optical Devices
- Quantum Mechanics and Applications
- Physics of Superconductivity and Magnetism
- Semiconductor materials and devices
- Quantum optics and atomic interactions
- Semiconductor Lasers and Optical Devices
- Neural Networks and Reservoir Computing
- Cloud Computing and Resource Management
- Atomic and Subatomic Physics Research
- Mechanical and Optical Resonators
- Acoustic Wave Resonator Technologies
- Magneto-Optical Properties and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Graphene research and applications
- Electronic and Structural Properties of Oxides
- Additive Manufacturing and 3D Printing Technologies
- Distributed and Parallel Computing Systems
- Advanced Electron Microscopy Techniques and Applications
IBM (United States)
2013-2023
IBM Research - Thomas J. Watson Research Center
2016-2019
Harvard University
2006-2012
Abstract We improve the quality of quantum circuits on superconducting computing systems, as measured by volume (QV), with a combination dynamical decoupling, compiler optimizations, shorter two-qubit gates, and excited state promoted readout. This result shows that path to larger QV systems requires simultaneous increase coherence, control gate fidelities, measurement smarter software which takes into account hardware details, thereby demonstrating need continue co-design stack for...
The concept of quantum computing has inspired a whole new generation scientists, including physicists, engineers, and computer to fundamentally change the landscape information technology. With experimental demonstrations stretching back more than two decades, community achieved major milestone over past few years: ability build systems that are limits what can be classically simulated, which enable cloud-based research for wide range thus increasing pool talent exploring early systems....
Two distinct types of magnetoresistance oscillations are observed in two electronic Fabry-Perot interferometers different sizes the integer quantum Hall regime. Measuring these as a function magnetic field and gate voltages, we describe three signatures that distinguish types. The $2.0\text{ }\ensuremath{\mu}{\text{m}}^{2}$ device understood to arise from Coulomb blockade mechanism those an $18\text{ Aharonov-Bohm mechanism. This work clarifies, provides ways distinguish, demonstrates...
An 18-qubit GHZ state with multipartite entanglement is prepared and measured on a 20-qubit device. The detection technique used, which based measuring multiple quantum coherences, robust to noise only requires the population in ground state.
The resonator-induced phase (RIP) gate is an all-microwave multiqubit entangling that allows a high degree of flexibility in qubit frequencies, making it attractive for quantum operations large-scale architectures. We experimentally realize the RIP with four superconducting qubits three-dimensional circuit-QED architecture, demonstrating high-fidelity controlled-z (cz) gates between all possible pairs from two different 4-qubit devices pair subspaces. These are arranged within wide range...
Superconducting qubits are sensitive to a variety of loss mechanisms including dielectric from interfaces. By changing the physical footprint qubit it is possible modulate sensitivity surface loss. Here we show systematic study planar superconducting transmons differing footprints optimize design for maximum coherence. We find that with small limited by and large other which currently not understood.
We improve the quality of quantum circuits on superconducting computing systems, as measured by volume, with a combination dynamical decoupling, compiler optimizations, shorter two-qubit gates, and excited state promoted readout. This result shows that path to larger volume systems requires simultaneous increase coherence, control gate fidelities, measurement smarter software which takes into account hardware details, thereby demonstrating need continue co-design stack for foreseeable future.
Scaling the number of qubits while maintaining high-fidelity quantum gates remains a key challenge for computing. Presently, superconducting processors with >50 are actively available. For these systems, fixed-frequency transmons attractive because their long coherence and noise immunity. However, scaling architectures proves challenging precise relative frequency requirements. Here, we use laser annealing to selectively tune transmon into desired patterns. Statistics over hundreds...
The effects of ionizing radiation on superconducting qubits are studied, showing that the two-level systems near a qubit can be ``scrambled,'' resulting in long-lasting changes to lifetime qubit.
We report measurements of current noise in single-layer and multilayer graphene devices. In four devices, including a $p\mathrm{\text{\ensuremath{-}}}n$ junction, the Fano factor remains constant to within $\ifmmode\pm\else\textpm\fi{}10%$ upon varying carrier type density, averages between 0.35 0.38. The device is found decrease from maximal value 0.33 at charge-neutrality point 0.25 high density. These results are compared theories for shot ballistic disordered graphene.
We report measurements of the cross correlation between temporal current fluctuations in two capacitively coupled quantum dots Coulomb blockade regime. The sign cross-spectral density is found to be tunable by gate voltage and source-drain bias. find good agreement with data including an interdot interaction a sequential-tunneling model.
We investigate nonlinear transport in electronic Fabry-Pérot interferometers the integer quantum Hall regime. For sufficiently large that Coulomb blockade effects are absent, a checkerboardlike pattern of conductance oscillations as function dc bias and perpendicular magnetic field is observed. Edge-state velocities extracted from checkerboard data compared to model calculations found be consistent with crossover skipping orbits at low fields E-vector x B-vector drift high fields....
Resistance oscillations in electronic Fabry-Perot interferometers near fractional quantum Hall (FQH) filling factors $1/3$, $2/3$, $4/3$, and $5/3$ the constrictions are compared to those integer (IQH) same devices at gate voltages. Two-dimensional plots of resistance versus voltage magnetic field indicate that all Coulomb dominated. A charging-model analysis gate-voltage periods yields an effective tunneling charge ${e}^{*}\ensuremath{\approx}e/3$ for FQH states...
Decoherence of superconducting transmon qubits is purported to be consistent with surface loss from two-level systems on the substrate surface. Here, we present a study in devices, explicitly designed have varying sensitivities different contributors. Our experiments also encompass two particular sapphire substrates, which reveal onset yet unknown additional mechanism outside for one substrates. Tests across wafers and devices demonstrate substantial variation, emphasize importance testing...
A promising approach for constructing networks of solid-state qubits quantum information processing is the circuit QED architecture. In such a setup, speed at which qubit measurement can be turned on and off limited by time constant readout resonator. The authors demonstrate method populating depopulating this resonator quickly precisely, without prior knowledge qubit's state---an elegant practical technique to help up computer.
We report simultaneous measurement of shot noise and dc transport in a quantum point contact as function source-drain bias, gate voltage, in-plane magnetic field. Shot at zero field exhibits an asymmetry related to the 0.7 structure conductance. The evolves smoothly into symmetric signature spin-resolved electron transmission high Comparison phenomenological model with density-dependent level splitting yields good quantitative agreement.
We describe the construction and operation of a two-channel noise detection system for measuring power cross spectral densities current fluctuations near 2MHz in electronic devices at low temperatures. The employs cryogenic amplification fast Fourier transform based measurement. gain electron temperature are calibrated using Johnson thermometry. Full shot 100pA can be resolved with an integration time 10s. report demonstration measurement bias-dependent gate defined GaAs∕AlGaAs quantum point contact.
We report measurements of current noise auto- and cross correlation in a tunable quantum dot with two or three leads. As the Coulomb blockade is lifted at finite source-drain bias, autocorrelation evolves from super- to sub-Poissonian two-lead case, positive negative three-lead consistent transport through multiple levels. Cross correlations are found be proportional excess Poissonian value limit weak output tunneling.
Superconducting qubits are sensitive to a variety of loss mechanisms which include dielectric from interfaces. The calculation participation near the key interfaces planar designs can be accomplished through an analytical description electric field density based on conformal mapping. In this way, two-dimensional approximation coplanar waveguide and capacitor produces values as function depth top metallization layer well volume within given thickness surface by reducing problem integration...
Scaling the number of qubits while maintaining high-fidelity quantum gates remains a key challenge for computing. Presently, superconducting processors with >50-qubits are actively available. For such systems, fixed-frequency transmons attractive due to their long coherence and noise immunity. However, scaling architectures proves challenging precise relative frequency requirements. Here we employ laser annealing selectively tune transmon into desired patterns. Statistics over hundreds...
We investigate dynamic nuclear polarization in quantum point contacts (QPCs) the integer and fractional Hall regimes. Following application of a dc bias, plateaus QPC shift symmetrically about half filling lowest Landau level, ν=1/2, suggesting an interpretation terms composite fermions. Polarizing detecting at different factors indicates that Zeeman energy is reduced by induced polarization. Mapping effects from to regimes extends fermion picture include hyperfine coupling.
Superconducting qubit lifetimes must be both long and stable to provide an adequate foundation for quantum computing. This stability is imperiled by two-level systems (TLSs), currently a dominant loss mechanism, which exhibit slow spectral dynamics that destabilize on hour timescales. Stability also threatened at millisecond timescales, where ionizing radiation has recently been found cause bursts of correlated multi-qubit decays, complicating error correction. Here we study TLS 27-qubit...