Martin Sandberg

IBM (United States)

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David P. Pappas

Rigetti Computing (United States)

Michael Vissers

National Institute of Standards and Technology

Martin Weides

University of Glasgow

Per Delsing

Chalmers University of Technology

Jiansong Gao

National Institute of Standards and Technology

C. M. Wilson

Goddard Space Flight Center

Markus Brink

IBM (United States)

Fredrik Persson

Sahlgrenska University Hospital

Göran Johansson

Chalmers University of Technology

Jerry M. Chow

IBM (United States)

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IBM (United States)

IBM Research - Thomas J. Watson Research Center

National Institute of Standards and Technology

IBM Research - Almaden

Karlsruhe Institute of Technology

Chalmers University of Technology

University of Colorado Boulder

Massachusetts Institute of Technology

Stanford University

National Institute of Standards

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Exploring circuit quantum electrodynamics using a widely tunable superconducting resonator

Physica Scripta (2009)

Martin Sandberg Fredrik Persson I.-C. Hoi C. M. Wilson Per Delsing

We have fabricated and characterized systems consisting of superconducting quantum bits (qubits) of the transmon type, coupled to a tunable transmission line resonator. The resonator consists of a superconducting quarter wavelength coplanar waveguide (CPW) resonator that is made tunable by terminating the transmission line to ground through a superconducting quantum interference device (SQUID). Here we present measurements on two devices where we observe Rabi oscillations as we drive the qubit, and vacuum Rabi splitting both as we tune the qubits into resonance with the resonator and as we tune the resonator into resonance with the qubits. We also observe coherent interaction between two resonant qubits. In addition, we demonstrate that we can calculate the response very accurately using a multilevel Hamiltonian.

Transmon

Rabi cycle

Coplanar waveguide

Circuit quantum electrodynamics

Helical resonator

10.1088/0031-8949/2009/t137/014018

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Citations (25)

Open Secure Office Project : Wireless Sensor Network

R. Andersson Martin Sandberg László Urszuly

In recent years, the development of wireless sensor networks has made a great progress. Early projects focused on replacement of existing systems equipped with wires. These systems started out as s ...

Source

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Airborne laser radar: systems and methods for reconnaissance and terrain modeling

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1999)

Ove Steinvall Ulf Soederman Simon Ahlberg Martin Sandberg Dietmar Letalick

Recently a number of airborne nadir scanning laser radars have been developed for both military and civilian applications. These have range resolutions on the order of 10 cm but relatively moderate area coverage rates, in the range 1000 - 10,000 m²/s (3.6 - 36 km²/h) when operating in a high resolution mode with 0.25 m spot distance. Technology development in laser sources, scanning techniques and signal processing will probably improve the area coverage substantially and lead to compact systems suitable for new applications, including the use in UAV:s. Present nadir capability could be combined with a forward looking capability for guidance and obstacle avoidance in autonomous or semi-autonomous systems. The paper will investigate the potential performance of such combined systems using state-of-the-art lasers and receiver technology. Among the applications for both military and civilian users we note the collection of 3-D data for terrain modeling and object recognition. For these functions signal processing using multiple echo and intensity information is of great value as well as adding passive senor information. Full wave form processing will further improve the information for example to characterize trees. The use of high resolution 3-D data in synthetic environments is obvious and will be discussed. Experimental data collected with a commercial laser system, TopEye, developed by Saab Dynamics, will be shown and some image examples will be discussed in relation to different applications.

Nadir

Data Processing

10.1117/12.351338

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Dressed relaxation and dephasing in a strongly driven two-level system

Physical Review B (2010)

C. M. Wilson Göran Johansson T. Duty Fredrik Persson Martin Sandberg

We study relaxation and dephasing in a strongly driven two-level system interacting with its environment. We develop a theory which gives a straightforward physical picture of the complex dynamics of the system in terms of dressed states. In addition to the dressing of the energy diagram, we describe the dressing of relaxation and dephasing. We find a good quantitative agreement between the theoretical calculations and measurements of a superconducting qubit driven by an intense microwave field. The competition of various processes leads to a rich structure in the observed behavior, including signatures of population inversion.

Dephasing

Population inversion

10.1103/physrevb.81.024520

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Citations (69)

Fast readout of a single Cooper-pair box using its quantum capacitance

Physical Review B (2010)

Fredrik Persson C. M. Wilson Martin Sandberg Per Delsing

We have fabricated a single Cooper-pair box (SCB) together with an on-chip lumped element resonator. By utilizing the quantum capacitance of the SCB, its state can be read out by detecting the phase of a radio-frequency signal reflected off the resonator. The resonator was optimized for fast readout. By studying quasiparticle tunneling events in the SCB, we have characterized the performance of the readout and found that we can perform a single-shot parity measurement, with a signal-to-noise ratio of 1, in approximately 50 ns. This is an order of magnitude faster than previously reported measurements.

Cooper pair

Parasitic capacitance

SIGNAL (programming language)

10.1103/physrevb.82.134533

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Citations (23)

Radiation-suppressed superconducting quantum bit in a planar geometry

Applied Physics Letters (2013)

Martin Sandberg Michael Vissers Thomas Ohki Jiansong Gao José Aumentado

We present a superconducting qubit design that is fabricated in a 2D geometry over a superconducting ground plane to enhance the lifetime. The qubit is coupled to a microstrip resonator for readout. The circuit is fabricated on a silicon substrate using low loss, stoichiometric titanium nitride for capacitor pads and small, shadow-evaporated aluminum/aluminum-oxide junctions. We observe qubit relaxation and coherence times ($T_1$ and $T_2$) of 11.7 $\pm$ 0.2 $μ$s and 8.7 $\pm$ 0.3 $μ$s, respectively. Calculations show that the proximity of the superconducting plane suppresses the otherwise high radiation loss of the qubit. A significant increase in $T_1$ is projected for a reduced qubit-to-superconducting plane separation.

10.1063/1.4792698

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Citations (32)

Coherence in a transmon qubit with epitaxial tunnel junctions

Applied Physics Letters (2011)

Martin Weides Jeffrey S. Kline Michael Vissers Martin Sandberg David Wisbey

We developed transmon qubits based on epitaxial tunnel junctions and interdigitated capacitors. This multileveled qubit, patterned by use of all-optical lithography, is a step towards scalable qubits with a high integration density. The relaxation time T1 is 0.72−0.86 μs and the ensemble dephasing time T2* is slightly larger than T1. The dephasing time T2 (1.36 μs) is nearly energy-relaxation-limited. Qubit spectroscopy yields weaker level splitting than observed in qubits with amorphous barriers in equivalent-size junctions. The qubit’s inferred microwave loss closely matches the weighted losses of the individual elements (junction, wiring dielectric, and interdigitated capacitor), determined by independent resonator measurements.

Transmon

Dephasing

10.1063/1.3672000

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Citations (34)

Coherence Times of Dressed States of a Superconducting Qubit under Extreme Driving

Physical Review Letters (2007)

C. M. Wilson T. Duty Fredrik Persson Martin Sandberg Göran Johansson

We measure longitudinal dressed states of a superconducting qubit, the single Cooper-pair box, and an intense microwave field. The dressed states represent the hybridization of the qubit and photon degrees of freedom and appear as avoided level crossings in the combined energy diagram. By embedding the circuit in an rf oscillator, we directly probe the dressed states. We measure their dressed gap as a function of photon number and microwave amplitude, finding good agreement with theory. In addition, we extract the relaxation and dephasing rates of these states.

Charge qubit

Dephasing

Flux qubit

Cooper pair

10.1103/physrevlett.98.257003

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Citations (153)

Measuring a Topological Transition in an Artificial Spin-1/2System

Physical Review Letters (2014)

M. D. Schroer Michael Kolodrubetz William Kindel Martin Sandberg Jian Gao

We present measurements of a topological property, the Chern number (C1), of a closed manifold in the space of two-level system Hamiltonians, where the two-level system is formed from a superconducting qubit. We manipulate the parameters of the Hamiltonian of the superconducting qubit along paths in the manifold and extract C1 from the nonadiabatic response of the qubit. By adjusting the manifold such that a degeneracy in the Hamiltonian passes from inside to outside the manifold, we observe a topological transition C1=1→0. Our measurement of C1 is quantized to within 2% on either side of the transition.Received 28 April 2014DOI:https://doi.org/10.1103/PhysRevLett.113.050402© 2014 American Physical Society

Hamiltonian (control theory)

Manifold (fluid mechanics)

Degeneracy (biology)

Topological index

10.1103/physrevlett.113.050402

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Citations (142)

Concentric transmon qubit featuring fast tunability and an anisotropic magnetic dipole moment

Applied Physics Letters (2016)

Jochen Braumüller Martin Sandberg Michael Vissers Andre Schneider Steffen Schlör

We present a planar qubit design based on a superconducting circuit that we call concentric transmon. While employing a straightforward fabrication process using Al evaporation and lift-off lithography, we observe qubit lifetimes and coherence times in the order of 10 μs. We systematically characterize loss channels such as incoherent dielectric loss, Purcell decay and radiative losses. The implementation of a gradiometric SQUID loop allows for a fast tuning of the qubit transition frequency and therefore for full tomographic control of the quantum circuit. Due to the large loop size, the presented qubit architecture features a strongly increased magnetic dipole moment as compared to conventional transmon designs. This renders the concentric transmon a promising candidate to establish a site-selective passive direct Ẑ coupling between neighboring qubits, being a pending quest in the field of quantum simulation.

Transmon

10.1063/1.4940230

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Citations (50)