II. Applications of the Josephson Effect

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R. Gross, A. Marx, and F. Deppe © Walther-Meißner-Institut (2001 - 2013) II. Applications of the Josephson Effect AS-Chap. 4 - 2 large number of analog and digital applications: • I s m = I s m B : magnetic field sensors (SQUIDs) (ch. 4) • β C ≫ 1: bistability: zero/voltage state switching devices, Josephson computer (ch. 5) • 2 nd Josephson equation dφ/dt = 2eV/ħ VCO, voltage standard (ch. 6) • nonlinear IVC mixers up to THz, oscillators (ch. 7) • macroscopic quantum behavior superconducting qubits (ch. 9)
R. Gross, A. Marx, and F. Deppe © Walther-Meißner-Institut (2001 - 2013) 4. Superconducting Quantum Interference Devices Superconducting Quantum Interference Devices = SQUID single Josephson junction as can be used as magnetic field sensor: I s m = I s m B - sensitivity: dI s /dΦ ≈ I s m /Φ 0 = I s m /B 0 t B L increase t B L to increase sensitivity • superconducting loop with one or more Josephson junctions relevant area: loop area • dual or multi-beam interference: Superconducting Quantum Interference Devices (SQUIDs) • relevant physics: flux quantization in superconducting loops and Josephson effect • SQUIDs = most sensitive detectors for magnetic flux • can detect every quantity that can be converted into magnetic flux: magnetic field, field gradient, current, voltage, displacement, … • most relevant types of SQUIDs: direct current (dc) and radio frequency (rf) SQUIDs • dc-SQUIDs: highest energy sensitivity at low temperatures AS-Chap. 4 - 3
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II. Applications of the Josephson Effect

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