Mark B. Ketchen

High‐resolution scanning SQUID microscope

We have combined a novel low temperature positioning mechanism with a single‐chip miniature superconducting quantum interference device (SQUID) magnetometer to form an extremely sensitive new magnetic microscope, with a demonstrated spatial resolution of ∼10 μm. The design and operation of this scanning SQUID microscope will be described. The absolute calibration of this instrument with an ideal point source, a single vortex trapped in a superconducting film, will be presented, and a representative application will be discussed.

Ultra‐low‐noise tunnel junction dc SQUID with a tightly coupled planar input coil

We present a new superconducting quantum interference device (SQUID) that combines ultra‐low‐noise performance with tight coupling to a useable input coil. The inductive loop of the SQUID consists of a superconducting square washer that is slit in a low inductance fashion from its central hole to an outside edge where two Josephson tunnel junctions are incorporated. The inductance of the SQUID is about 90 pH, and each junction has a critical current of 15 μA and a resistive shunt of 4.5 Ω. The 190‐nH input coil is a planar spiral of 50 turns situated immediately above the washer and coupled to the SQUID with a coupling constant k2 of 0.86. The SQUID has a minimum coupled energy sensitivity of 19h at 4.2 K and 8h at 1.5 K, in good agreement with theory. The crossover between white and low frequency noise occurs at ∼250 Hz.

Superconducting qubit in a waveguide cavity with a coherence time approaching 0.1 ms

We report a superconducting artificial atom with a coherence time of

Low noise YBa2Cu3O7-δ grain boundary junction dc SQUIDs

{T}_{2}^{*}=92

Low noise YBa sub 2 Cu sub 3 O sub 7 minus. delta. grain boundary junction dc SQUIDs

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Subpicosecond electrical pulse generation using photoconductive switches with long carrier lifetimes

s and energy relaxation time

Pairing Symmetry in Single-Layer Tetragonal Tl2Ba2CuOβ+δ Superconductors

{T}_{1}=70

Design, fabrication, and performance of integrated miniature SQUID susceptometers

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