Lars Tornberg

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We present measurements of single-qubit gate errors for a superconducting qubit. Results from quantum process tomography and randomized benchmarking are compared with gate errors obtained from a double pi pulse experiment. Randomized benchmarking reveals a minimum average gate error of 1.1+/-0.3% and a simple exponential dependence of fidelity on the number(More)
We investigate the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom which is strongly coupled to a coplanar transmission line. The interaction between the fields and atom produces an effective cross-Kerr coupling. We demonstrate average cross-Kerr phase shifts of up to 20 degrees per photon with(More)
We realize indirect partial measurement of a transmon qubit in circuit quantum electrodynamics by interaction with an ancilla qubit and projective ancilla measurement with a dedicated readout resonator. Accurate control of the interaction and ancilla measurement basis allows tailoring the measurement strength and operator. The tradeoff between measurement(More)
The ability to nondestructively detect the presence of a single, traveling photon has been a long-standing goal in optics, with applications in quantum information and measurement. Realizing such a detector is complicated by the fact that photon-photon interactions are typically very weak. At microwave frequencies, very strong effective photon-photon(More)
L. Tornberg,1 Sh. Barzanjeh,2 and David P. DiVincenzo2,3,4 1Chalmers University of Technology, SE-41296 Gothenburg, Sweden 2Institute for Quantum Information, RWTH Aachen University, D-52056 Aachen, Germany 3Peter Grünberg Institute: Theoretical Nanoelectronics, Research Center Jülich, 52428 Jülich, Germany 4Jülich-Aachen Research Alliance, Fundamentals of(More)
We analyze the dispersive readout of superconducting charge and flux qubits as a quantum measurement process. The measurement oscillator frequency is considered much lower than the qubit frequency. This regime is interesting because large detuning allows for strong coupling between the measurement oscillator and the signal transmission line, thus allowing(More)
We propose an offline method to match tracked objects from two sensors in complex and real life traffic scenarios, which can be used to build an automatic system for offline sensor verification of advanced driver assistance systems and autonomous driving. Detected objects in each of the sensors are described by a dynamic state vector representing their(More)
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