Measurement of Quantum Phase-Slips in Josephson Junction Chains

Quantum phase-slip dynamics in Josephson junction chains could provide the basis for the realization of a new type of topologically protected qubit [1] or for the implementation of a new current standard [2]. I will present measurements of the effect of quantum phase-slips on the ground state of a Josephson junction chain. We can tune in situ the strength of the phase-slips. These phase-slips are the result of fluctuations induced by the finite charging energy of each junction in the chain. Our measurements demonstrate that a Josephson junction chain under phase bias constraint behaves in a \textit{collective }way [3]. I will also show evidence of coherent phase-slip interference, the so called Aharonov-Casher effect. This phenomenon is the dual of the well known Aharonov-Bohm interference.\\[4pt] In collaboration with I.M. Pop, Institut Neel, C.N.R.S. and Universite Joseph Fourier, BP 166, 38042 Grenoble, France; I. Protopopov, L. D. Landau Institute for Theoretical Physics, Kosygin str. 2, Moscow 119334, Russia and Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie, 76021 Karlsruhe, Germany; and F. Lecocq, Z. Peng, B. Pannetier, O. Buisson, Institut Neel, C.N.R.S. and Universite Joseph Fourier. \\[4pt] [1] I. M. Pop, O. Buisson, K. Hasselbach, I. Protopopov, W. Guichard and B. Pannetier, Phys. Rev. B, 78, 104504(2008) \\[0pt] [2] W. Guichard and F. Hekking, Phys. Rev. B 81, 064508 (2010) \\[0pt] [3] I. M. Pop, I. Protopopov, F. Lecocq, Z. Peng, B. Pannetier, O. Buisson and W. Guichard, Nature Physics, 6, 589 (2010).