A5008314339- Quantum Information and Cryptography
- Quantum and electron transport phenomena
- Quantum Computing Algorithms and Architecture
- Physics of Superconductivity and Magnetism
- Mechanical and Optical Resonators
- Quantum Mechanics and Applications
- Superconducting and THz Device Technology
- Photonic and Optical Devices
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum optics and atomic interactions
- Particle accelerators and beam dynamics
- Gyrotron and Vacuum Electronics Research
- Neural Networks and Reservoir Computing
- Advanced Frequency and Time Standards
- Advancements in Semiconductor Devices and Circuit Design
- Superconducting Materials and Applications
- Advanced Thermodynamics and Statistical Mechanics
- Laser-Matter Interactions and Applications
- Semiconductor Quantum Structures and Devices
- Atomic and Subatomic Physics Research
- Microwave and Dielectric Measurement Techniques
- Surface and Thin Film Phenomena
- Optical Network Technologies
- Radio Frequency Integrated Circuit Design
- Microwave Engineering and Waveguides
University of Waterloo
2014-2024
University of California, Santa Barbara
2010-2014
California NanoSystems Institute
2011-2013
University of California, Berkeley
2011-2012
Technical University of Munich
2008-2010
Bavarian Academy of Sciences and Humanities
2008-2010
This article provides an introduction to surface code quantum computing. We first estimate the size and speed of a computer. then introduce concept stabilizer, using two qubits, extend this stabilizers acting on two-dimensional array physical which we implement code. next describe how logical qubits are formed in give numerical estimates their fault-tolerance. outline physically moved array, qubit braid transformations constructed, between is equivalent controlled-NOT. single-qubit Hadamard,...
The von Neumann architecture for a classical computer comprises central processing unit and memory holding instructions data. We demonstrate quantum that exchanges data with random-access integrated on chip, stored computer. test our machine by executing codes involve seven elements: Two superconducting qubits coupled through bus, two memories, zeroing registers. vital algorithms computing are demonstrated, the Fourier transform, 66% process fidelity, three-qubit Toffoli-class OR phase gate,...
We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high powers over 1 low powers, best power results approaching 2 million, corresponding to ~1 photon in resonator. These are achieved by controllably producing very smooth clean interfaces between resonators' aluminum metallization underlying single crystal sapphire substrate. Additionally, we a method for analyzing resonator response, which can directly...
We find that stray infrared light from the 4 K stage in a cryostat can cause significant loss superconducting resonators and qubits. For devices shielded only metal box, we measured with quality factors Q = 10^5 qubits energy relaxation times T_1=120 ns, consistent light-induced quasiparticle density of 170-230 \mu m^{-3}. By adding second black shield at sample temperature, found about an order magnitude improvement performance no sensitivity to radiation. also tested various shielding...
Quantum entanglement, one of the defining features quantum mechanics, has been demonstrated in a variety nonlinear spinlike systems. entanglement linear systems proven significantly more challenging, as intrinsic energy level degeneracy associated with linearity makes control difficult. Here we demonstrate photon states two independent microwave resonators, creating $N$-photon NOON (entangled $|N0⟩+|0N⟩$) benchmark demonstration. We use superconducting circuit that includes Josephson qubits...
We demonstrate a superconducting resonator with variable coupling to measurement transmission line. The can be adjusted through zero photon emission rate 1000 times the intrinsic decay rate. catch and release of photons in resonator, as well control nonclassical Fock states. also dynamical waveform from key functionality that will enable high-fidelity quantum state transfer between distant resonators or qubits.
Losses in superconducting planar resonators are presently assumed to predominantly arise from surface-oxide dissipation, due experimental losses varying with choice of materials. We model and simulate the magnitude loss interface surfaces resonator investigate dependence on power, geometry, dimensions. Surprisingly, dominant surface is found metal-substrate substrate-air interfaces. This result will be useful guiding device optimization, even conventional
We introduce a systematic formalism for two-resonator circuit QED, where two on-chip microwave resonators are simultaneously coupled to one superconducting qubit. Within this framework, we demonstrate that the qubit can function as quantum switch between resonators, which assumed be originally independent. In three-circuit network, mediates geometric second-order interaction otherwise decoupled resonators. dispersive regime, it also gives rise dynamic perturbative interaction. The and...
Minimizing phase and other errors in experimental quantum gates allows higher fidelity processing. To quantify correct for errors, particular, we have developed an metrology---amplified error (APE) pulses---that amplifies helps identify general multilevel qubit architectures. In order to both amplitude specific virtual transitions leakage outside of the manifold, implement ``half derivative,'' simplification derivative reduction by adiabatic gate (DRAG) control theory. The are lowered about...
We experimentally demonstrate quantum process tomography of controlled-Z and controlled-NOT gates using capacitively coupled superconducting phase qubits. These are realized by the $|2⟩$ state qubit. obtain a fidelity 0.70 for controlled 0.56 gate, with loss mostly due to single-qubit decoherence. The gate is also used two-qubit Deutsch-Jozsa algorithm single function query.
Quasiparticles are an important decoherence mechanism in superconducting qubits, and can be described with a complex admittance that is generalization of the Mattis-Bardeen theory. By injecting nonequilibrium quasiparticles tunnel junction, we verify qualitatively expected change decay rate transition frequency phase qubit. With their relative agreement to within 4 % prediction, theory reliably used infer quasiparticle density. We describe how settling may allow determination whether qubit...
Quantum computing architectures are on the verge of scalability, a key requirement for implementation universal quantum computer. The next stage in this quest is realization error correction codes, which will mitigate impact faulty information Architectures with ten or more bits (qubits) have been realized using trapped ions and superconducting circuits. While these implementations potentially scalable, true scalability require systems engineering to combine classical hardware. One...
We propose an architecture for quantum computing based on superconducting circuits, where on-chip planar microwave resonators are arranged in a two-dimensional grid with qubit at each intersection. This allows any two qubits the to be coupled swapping overhead independent of their distance. demonstrate that this approach encompasses fundamental elements scalable fault-tolerant quantum-computing architecture.
Quantum state reconstruction of weak propagating microwaves to date requires the use linear amplifiers. We introduce a theory which, even in presence significant amplifier noise, allows one these devices for measuring all quadrature moments quantum based on cross correlations from dual-path amplification setup. Simultaneously, detector noise properties are determined, allowing tomography. demonstrate feasibility our novel concept by proof-of-principle experiments with classical mixtures...
We analyze the detection of itinerant photons using a quantum non-demolition (QND) measurement. show that backaction due to continuous measurement imposes limit on detector efficiency in such scheme. illustrate this setup where signal have enter cavity order be detected dispersively. In approach, is phase shift imparted an intense beam passing through second mode. The restrictions fidelity are consequence Quantum Zeno effect, and we discuss both analytical results trajectory simulations process.
We use a correlation function analysis of the field quadratures to characterize both blackbody radiation emitted by $50\text{ }\text{ }\ensuremath{\Omega}$ load resistor and quantum properties two types beam splitters in microwave regime. To this end, we first study vacuum fluctuations as frequency Planck spectroscopy experiment then measure covariance matrix weak thermal states. Our results provide direct experimental evidence that represent fundamental minimum noise added splitter any...
We measure the dependence of qubit phase coherence and flux noise on inductor loop geometry. While wider traces change neither power spectrum nor dephasing time, increased inductance leads to a simultaneous increase in both. Using our new tomographic protocol for measuring low frequency noise, we make direct comparison between decay, finding agreement within 10% theory.
Quantum bits (qubits) with long coherence times are an important element for the implementation of medium- and large-scale quantum computers. In case superconducting planar qubits, understanding improving qubits' quality can be achieved by studying resonators. this paper, we fabricate characterize coplanar waveguide resonators made from aluminum thin films deposited on silicon substrates. We perform three different substrate surface treatments prior to deposition: one chemical treatment...
Superconducting qubits probe environmental defects such as nonequilibrium quasiparticles, an important source of decoherence. We show that "hot" with energies above the superconducting gap, affect differently from quasiparticles at implying can dynamic quasiparticle energy distribution. For hot we predict a non-negligible increase in qubit excited state probability Pe. By injecting into qubit, experimentally measure Pe semiquantitative agreement model and rule out typically assumed thermal
We present a theoretical treatment for the dissipative two-resonator circuit quantum electrodynamics setup referred to as switch. There, switchable coupling between two superconducting resonators is mediated by qubit operating in dispersive regime, where transition frequency far detuned from those of resonators. derive an effective Hamiltonian switch beyond rotating-wave approximation and provide detailed study dynamics. As central finding, we analytically how affects even if has no...