A5010126138- Quantum Information and Cryptography
- Quantum and electron transport phenomena
- German Literature and Culture Studies
- Quantum Computing Algorithms and Architecture
- Corporate Governance and Law
- Law and Political Science
- Diverse Scientific and Economic Studies
- Cold Atom Physics and Bose-Einstein Condensates
- Diverse Legal and Medical Studies
- Quantum optics and atomic interactions
- Medical and Health Sciences Research
- Mechanical and Optical Resonators
- Quantum Mechanics and Applications
- Physics of Superconductivity and Magnetism
- Criminal Law and Policy
- Digitalization, Law, and Regulation
- Molecular Junctions and Nanostructures
- Photonic and Optical Devices
- Atomic and Subatomic Physics Research
- Spectroscopy and Quantum Chemical Studies
- Public Administration and Political Analysis
- Semiconductor Quantum Structures and Devices
- Laser-Matter Interactions and Applications
- Taxation and Legal Issues
- Advanced Thermodynamics and Statistical Mechanics
Northwestern University
2016-2025
Ludwig-Maximilians-Universität München
2018-2024
University of Tübingen
2018-2024
Karlsruhe University of Education
2023-2024
RAG Aktiengesellschaft (Germany)
2018-2024
Altrecht GGZ
2019-2024
Praxis
2015-2024
Weatherford College
2024
Eckert & Ziegler (United States)
2023
Cornell University
2023
Short dephasing times pose one of the main challenges in realizing a quantum computer. Different approaches have been devised to cure this problem for superconducting qubits, prime example being operation such devices at optimal working points, so-called ``sweet spots.'' This latter approach led significant improvement ${T}_{2}$ Cooper pair box qubits [D. Vion et al., Science 296, 886 (2002)]. Here, we introduce new type qubit called ``transmon.'' Unlike charge qubit, transmon is designed...
The promise of single Cooper pair quantum circuits based on tunnel junctions for metrology and information applications is severely limited by the influence "offset" charges - random, slowly drifting microscopic inherent to many solid-state systems. By shunting a small junction with Josephson kinetic inductance series array large capacitance junctions, thereby ensuring that all superconducting islands are connected circuit at least one junction, we have realized new artificial atom which...
We present an experimental realization of the transmon qubit, which is improved superconducting charge qubit derived from Cooper pair box. experimentally verify predicted exponential suppression sensitivity to $1∕f$ noise. This removes leading source dephasing in qubits results homogeneously broadened transitions with relaxation and times microsecond range. Our systematic characterization spectrum, anharmonicity, dispersion shows excellent agreement theory.
We show that Franck-Condon physics leads to a significant current suppression at low bias voltages (termed blockade) in transport through single molecules with strong coupling between electronic and vibrational degrees of freedom. Transport this regime is characterized by remarkably large Fano factors (10(2)-10(3) for realistic parameters), which arise due avalanchelike electrons. Avalanches occur self-similar manner over wide range time scales, leading power-law dependences the noise on...
We present a detailed characterization of coherence in seven transmon qubits circuit QED architecture. find that spontaneous emission rates are strongly influenced by far off-resonant modes the cavity and can be understood within semiclassical model. A careful analysis qubit decay into microwave transmission-line accurately predict lifetimes over 2 orders magnitude time more than an octave frequency. Coherence times T1 T_{2};{*} microsecond reproducibly demonstrated.
Breaking time-reversal symmetry is a prerequisite for accessing certain interesting many-body states such as fractional quantum Hall states. For polaritons, charge neutrality prevents magnetic fields from providing direct symmetry-breaking mechanism and, similar to the situation in ultracold atomic gases, an effective field has be synthesized. We show that circuit-QED architecture, this can achieved by inserting simple superconducting circuits into resonator junctions. In presence of...
Nonequilibrium phase transitions, where the physical properties of a system change suddenly, are fundamental importance in condensed matter physics but not well understood. Such transitions now observed circuit quantum electrodynamics lattice, paving way for greater insight into exotic materials.
The \textit{heavy-fluxonium} circuit is a promising building block for superconducting quantum processors due to its long relaxation and dephasing time at the half-flux frustration point. However, suppressed charge matrix elements low transition frequency have made it challenging perform fast single-qubit gates using standard protocols. We report on new protocols reset, coherent control, readout, that allow high-quality operation of qubit with 14 MHz frequency, an order magnitude lower in...
The fluxonium qubit is a promising candidate for quantum computation due to its long coherence times and large anharmonicity. We present tunable coupler that realizes strong inductive coupling between two heavy-fluxonium qubits, each with approximately <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>50</a:mn></a:math>-MHz frequencies <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" overflow="scroll"><d:mn>5</d:mn></d:math>-GHz...
We present measurements of single-qubit gate errors for a superconducting qubit. Results from quantum process tomography and randomized benchmarking are compared with obtained double pi pulse experiment. Randomized reveals minimum average error 1.1+/-0.3% simple exponential dependence fidelity on the number gates. It shows that limits primarily imposed by qubit decoherence, in agreement theory.
Strong coupling of electronic and vibrational degrees freedom entails a low-bias suppression the current through single-molecule devices, termed Franck-Condon blockade. In limit slow relaxation, transport in Franck-Condon-blockade regime proceeds via avalanches large numbers electrons, which are interrupted by long waiting times without electron transfer. The consist smaller avalanches, leading to self-similar hierarchy terminates once number transferred electrons per avalanche becomes order...
We investigate the thermopower of single molecules weakly coupled to metallic leads. model molecule in terms relevant electronic orbitals phonons corresponding both internal vibrations and oscillations as a whole. The is computed by means rate equations including sequential-tunneling cotunneling processes. Under certain conditions, allows one access phononic excitation spectrum linear-response measurement. In particular, we find that phonon features are more pronounced for weak lead-molecule...
We assess experimentally the suitability of coupled transmission line resonators for studies quantum phase transitions light. have measured devices with low photon hopping rates t/2pi = 0.8MHz to quantify disorder in individual cavity frequencies. The observed is consistent small imperfections fabrication. studied dependence on geometry and used our results fabricate less than two parts 10^4. normal mode spectrum a high rate 31MHz shows little effect disorder, rendering resonator arrays good...
Abstract The Jaynes‐Cummings model describes the coupling between photons and a single two‐level atom in simplified representation of light‐matter interactions. In circuit QED, this is implemented by combining microwave resonators superconducting qubits on microchip with unprecedented experimental control. Arranging form lattice realizes new kind Hubbard model, Jaynes‐Cummings‐Hubbard which elementary excitations are polariton quasi‐particles. Due to genuine openness photonic systems, QED...
Regular arrays of electromagnetic resonators, in turn coupled coherently to individual quantum two-level systems, exhibit a phase transition polaritons from superfluid Mott-insulating phase. The critical behavior such Jaynes-Cummings lattice thus resembles the physics Bose-Hubbard model. We explore this analogy by elaborating on mean-field theory and presenting several useful mappings which pinpoint both similarities differences two models. show that field-theory approach can be applied...
Quasiparticle tunneling across a Josephson junction sets limit for the lifetime of superconducting qubit state. We develop general theory corresponding decay rate in controlled by magnetic flux. The flux affects quasiparticles amplitudes, thus making flux-dependent. is applicable an arbitrary quasiparticle distribution. It provides estimates rates practically important quantum circuits and also offers new way measuring phase-dependent admittance junction.
Superconducting order in a sufficiently narrow and infinitely long wire is destroyed at zero temperature by quantum fluctuations, which induce $2\pi$ slips of the phase parameter. However, finite-length coherent phase-slips would manifest themselves simply as shifts energy levels excitations spectrum an electrical circuit incorporating this wire. The higher probability amplitude, larger are shifts. Phase-slips occurring different locations along interfere with each other. Due to...
We implement a quantum optimal control algorithm based on automatic differentiation and harness the acceleration afforded by graphics processing units (GPUs). Automatic allows us to specify advanced optimization criteria incorporate them in process with ease. show that use of GPUs can speed up calculations more than an order magnitude. Our strategy facilitates efficient numerical simulations affordable desktop computers, exploration host constraints system parameters relevant real-life...
Qubit connectivity is an important property of a quantum processor, with ideal processor having random access -- the ability arbitrary qubit pairs to interact directly. Here, we implement superconducting information demonstrating universal operations on nine-bit memory, single transmon serving as central processor. The memory uses eigenmodes linear array coupled resonators. bits are superpositions vacuum and single-photon states, controlled by edge array. We selectively stimulate Rabi...
We autonomously stabilize arbitrary states of a qubit through parametric modulation the coupling between fixed frequency and resonator. The is achieved with tunable design, in which resonator are connected parallel to superconducting quantum interference device. This allows for quasistatic tuning qubit-cavity strength from 12 MHz more than 300 MHz. Additionally, can be dynamically modulated, allowing single-photon exchange 6 ns. Qubit coherence times exceeding 20 μs maintained over majority...