Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 18: Transport: Quantum Coherence and Quantum Information Systems - Theory (jointly with MA, HL)

MA 18.7: Talk

Tuesday, March 21, 2017, 11:00–11:15, HSZ 103

Proximity Effect in Normal-Metal Quasiparticle Traps — •Amin Hosseinkhani^1,2 and Ginaluigi Catelani¹ — ¹Peter Grunberg Institut (PGI-2), Forschungszentrum Jülich, Jülich, Germany — ²JARA-Institute for Quantum Information, RWTH Aachen University, Aachen, Germany

In many superconducting devices, including qubits, quasiparticle excitations are detrimental. A normal metal (N) in contact with a superconductor (S) can trap these excitations. However, the contact between N and S modifies the properties of both materials, a phenomenon known as proximity effect which has drawn attention since the '60s. Despite this long history, we find new analytical results for the density of states, which shows a square root threshold behavior at the minigap energy. In superconducting qubits, the trap must be placed far enough from a Josephson junction in order not to harm the qubit coherence. To estimate the minimum trap-junction separation, we study how the density of states in the superconductor depends on the distance from the trap. For high interface resistance between N and S, a separation of several (5-7) coherence lengths is sufficient.