A5001211524- Quantum and electron transport phenomena
- Quantum Information and Cryptography
- Physics of Superconductivity and Magnetism
- Quantum Computing Algorithms and Architecture
- Semiconductor Quantum Structures and Devices
- Iron-based superconductors research
- Quantum chaos and dynamical systems
- Quantum optics and atomic interactions
- Atomic and Subatomic Physics Research
- Quantum Mechanics and Applications
- Mechanical and Optical Resonators
- Cold Atom Physics and Bose-Einstein Condensates
- Advancements in Semiconductor Devices and Circuit Design
- Quantum many-body systems
- Topological Materials and Phenomena
- Corporate Taxation and Avoidance
- Photonic and Optical Devices
- Semiconductor materials and devices
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- Superconductivity in MgB2 and Alloys
- Theoretical and Computational Physics
- Surface and Thin Film Phenomena
- Semiconductor Lasers and Optical Devices
- Magnetic Field Sensors Techniques
University of Wisconsin–Madison
2015-2025
Moscow State University
2025
Lomonosov Moscow State University
2025
University of Wisconsin System
2021
Physical Sciences (United States)
2017
Wisconsin Institutes for Discovery
2017
University of Maryland, College Park
2017
Yale University
2005-2006
Massachusetts Institute of Technology
2004-2005
University of Minnesota
2002-2004
Fluxonium qubit is a promising elementary building block for quantum information processing due to its long coherence time combined with strong anharmonicity. In this paper, we realize 60-ns direct gate on two inductively coupled fluxoniums, which behave almost exactly as pair of transversely spin-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>1</a:mn><a:mo>/</a:mo><a:mn>2</a:mn></a:math> systems. The -gate fidelity, estimated using randomized...
We develop a theory of magneto-oscillations in the photoconductivity two-dimensional electron gas observed recent experiments. The effect is governed by change distribution function induced microwave radiation. analyze nonlinearity with respect to both dc field and power, as well temperature dependence determined inelastic relaxation rate.
We derive the quantum Boltzmann equation for two-dimensional electron gas in a magnetic field such that filling factor $\ensuremath{\nu}\ensuremath{\gg}1.$ This describes all of effects external fields on impurity collision integral including Shubnikov--de Haas oscillations, smooth part magnetoresistance, and nonlinear transport. Furthermore, we obtain quantitative results effect microwave radiation linear dc transport system. Our findings are relevant description oscillating resistivity...
We present a detailed description of two-band quasi-two-dimensional metals with $s$-wave superconducting (SC) and antiferromagnetic spin-density-wave (SDW) correlations. general approach use it to investigate the influence difference between shapes areas two Fermi surfaces on phase diagram. In particular, we determine conditions for coexistence SC SDW orders at different temperatures dopings. argue that conventional order coexists only very low $T$ in tiny range parameters. An extended...
Using general symmetry arguments and model calculations we analyze the superconducting gap in materials with multiple Fermi-surface pockets, applications to iron pnictides. We show that pnictides has an extended $s$-wave but is either nodeless or nodes, depending on interplay between intraband interband interactions. argue nodes emerge without a phase transition as tendency toward spin-density-wave order gets weaker. These findings provide way reconcile seemingly conflicting results of...
We describe an approach to the integrated control and measurement of a large-scale superconducting multiqubit array comprising up 108 physical qubits using proximal coprocessor based on Single Flux Quantum (SFQ) digital logic family. Coherent is realized by irradiating directly with classical bitstreams derived from optimal theory. Qubit performed Josephson photon counter, which provides access result projective quantum at millikelvin stage. analyze power budget footprint SFQ discuss...
Superconducting qubits are conventionally controlled with shaped microwave pulses from a carrier tone. This works well for small systems, but is difficult to scale up the millions of needed general-purpose quantum computer. Instead, authors suggest irradiating qubit trains quantized flux derived single (SFQ) digital logic. The generated by an SFQ driver circuit cofabricated on chip. work opens door tight integration array classical coprocessor, lower wiring heat load, latency, and overall...
Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting gated InAs-Al Josephson junction coplanar waveguide resonator, we demonstrate the use of wide-range gate-tunable element. We show that resonant frequency is controlled via inductance and non-linearity voltage-controlled non-dissipative as case with conventional Al-AlO$_{x}$ junctions. As gate voltage decreased, inductive...
Abstract We report a detailed characterization of two inductively coupled superconducting fluxonium qubits for implementing high-fidelity cross-resonance gates. Our circuit stands out because it behaves very closely to the case transversely spin-1/2 systems. In particular, generally unwanted static ZZ-term due non-computational transitions is nearly absent despite strong qubit-qubit hybridization. Spectroscopy reveals spurious LC-mode arising from combination coupling inductance and...
We consider phase transitions and potential coexistence of spin-density-wave (SDW) magnetic order extended $s$-wave $({s}^{+})$ superconducting within a two-band itinerant model iron pnictides in which SDW magnetism ${s}^{+}$ superconductivity are competing orders. show that depending on parameters, the transition between these two states is either first or involves an intermediate orders coexist. demonstrate such possible when incommensurate.
We consider the superfluid density ${\ensuremath{\rho}}_{s}(T)$ in a two-band superconductor with sign-changing extended $s$-wave symmetry $({s}^{+})$ presence of nonmagnetic impurities and apply results to Fe-pnictides. show that behavior is essentially same as an ordinary magnetic impurities. that, for moderate strong interband impurity scattering, behaves power law ${T}^{n}$ $n\ensuremath{\approx}1.6\textdiv{}2$ over wide range $T$. argue power-law consistent recent experiments on...
We study the emergent band topology of subgap Andreev bound states in three-terminal Josephson junctions. scrutinize symmetry constraints scattering matrix normal region connecting superconducting leads that enable topological nodal points spectrum states. When possesses time-reversal symmetry, gap closing occurs at special stationary are topologically trivial as they carry vanishing Berry fluxes. In contrast, for broken case we find monopoles curvature and corresponding phase transition...
Fast, high-fidelity measurement is a key ingredient for quantum error correction. Conventional approaches to the of superconducting qubits, involving linear amplification microwave probe tone followed by heterodyne detection at room temperature, do not scale well large system sizes. Here we introduce an alternative approach based on photon counter. We demonstrate raw single-shot fidelity 92%. Moreover, exploit intrinsic damping counter extract energy released process, allowing repeated...
A longstanding goal of quantum-computer architecture is to integrate control circuitry in a fault-tolerant and compact manner that will facilitate future scalable designs. In this paper, authors propose using resonant trains single flux quantum pulses produce fidelities excess 99.9% for 20-ns gate times. The provide one sharp kick per qubit oscillation period, analogous pumping up rider on swing by giving short push cycle.
Nonequilibrium quasiparticles represent a significant source of decoherence in superconducting quantum circuits. Here we investigate the mechanism quasiparticle poisoning devices subjected to local injection. We find that is dominated by propagation pair-breaking phonons across chip. characterize energy dependence timescale for poisoning. Finally, observe incorporation extensive normal metal traps leads more than order magnitude reduction loss given injected power.
We consider mesoscopic four-terminal Josephson junctions and study emergent topological properties of the Andreev subgap bands. use symmetry-constrained analysis for Wigner-Dyson classes scattering matrices to derive band dispersions. When matrix normal region connecting superconducting leads is energy independent, determinant formula spectrum can be reduced a palindromic equation that admits complete analytical solution. Band topology manifests with an appearance Weyl nodes which serve as...
Large scale quantum computing motivates the invention of two-qubit gate schemes that not only maximize fidelity but also draw minimal resources. In case superconducting qubits, weak anharmonicity transmons imposes profound constraints on design, leading to increased complexity devices and control protocols. Here we demonstrate a resource-efficient over interaction strongly-anharmonic fluxonium qubits. Namely, applying an off-resonant drive noncomputational transitions in pair...
The superconducting fluxonium qubit has a great potential for high-fidelity quantum gates with its long coherence times and strong anharmonicity at the half-flux-quantum sweet spot. However, current implementations of two-qubit compromise fluxonium's properties by requiring either temporary population noncomputational states or tuning magnetic flux off Here we realize fast all-microwave cross-resonance gate between two capacitively coupled fluxoniums dynamics well confined to computational...
We propose a random matrix theory to describe the influence of time-dependent external field on electron transport through open quantum dots. generation current by an oscillating for dot, connected two leads with equal chemical potentials. For low-frequency fields, our results correspond adiabatic charge pumping. Finite can be produced if system goes along closed loop in parameter space, which covers finite area. At high frequency, is even line space. This result explained same way as...
We develop a theory of nonlinear response to an electric field two-dimensional electron gas (2DEG) placed in classically strong magnetic field. The latter leads non-linear current-voltage characteristic at relatively weak origin the non-linearity is two-fold: formation non-equilibrium distribution function, and geometrical resonance inter-Landau-levels transitions rates. find dependence characteristics on relaxation rates 2DEG.
We present a systematic study of the microwave-induced oscillations in magnetoresistance two-dimensional electron gas for mixed disorder including both short-range and long-range components. The obtained photoconductivity tensor contains contributions four distinct transport mechanisms. show that photoresponse depends crucially on relative weight component disorder. Depending properties disorder, theory allows one to identify temperature range within which is dominated by mechanisms analyzed paper.
We analyze how disorder affects the transition temperature ${T}_{c}$ of ${s}^{+\ensuremath{-}}$ superconducting state in iron pnictides. The conventional wisdom is that should rapidly decrease with increasing inter-band nonmagnetic impurity scattering, but we show this behavior holds only overdoped region phase diagram. In underdoped regime, where superconductivity emerges from a pre-existing magnetic state, gives rise to two competing effects: breaking Cooper pairs, which tends reduce...
Random-matrix theory is used to study the mesoscopic fluctuations of excitation gap in a metal grain or quantum dot induced by proximity superconductor. We propose that probability distribution universal function rescaled units. Our analytical prediction for agrees well with exact diagonalization model Hamiltonian.
We investigate the effect of a spin-density wave (SDW) on $s_{\pm}$ superconductivity in Fe-based superconductors. show that, contrary to common wisdom, no nodes open at new, reconnected Fermi surfaces when hole and electron pockets fold down SDW state, despite fact that gap changes sign between two pockets. Instead, order parameter preserves its along newly formed surfaces. The familiar experimental signatures an symmetry are still preserved, although they appear mathematically different...
We study transport properties of a two-dimensional electron gas, placed in classically strong perpendicular magnetic field and constant oscillating in-plane electric fields. The analysis is based on quantum Boltzmann equation derived for weakly disordered gas. consider potential with both long- short-range correlations. Electron scattering off such disorder not limited to small change momentum direction, but occurs an arbitrary angle, including the backscattering. nonlinearity considered...