Quantum Dissociation of a Vortex-Antivortex Pair in a Long Josephson Junction

Abstract

The thermal and the quantum dissociation of a single vortex-antivortex (VAV) pair in an annular Josephson junction is experimentally observed and theoretically analyzed. In our experiments, the VAV pair is confined in a pinning potential controlled by external magnetic field and bias current. The dissociation of the pinned VAV pair manifests itself in a switching of the Josephson junction from the superconducting to the resistive state. The observed temperature and field dependence of the switching current distribution is in agreement with the analysis. The crossover from the thermal to the macroscopic quantum tunneling mechanism of dissociation occurs at a temperature of about 100 mK. We also predict the specific magnetic field dependence of the oscillatory energy levels of the pinned VAV state.

Quantum Dynamics of Vortices and Vortex Qubits

“…In this section we report on the experimental observation of thermal and the quantum dissociation of a single vortex-antivortex pair [37]. States containing many VAV pairs are relevant to thin superconducting films or large two-dimensional Josephson arrays close to the KosterlitzThouless transition [9].…”

“…We have theoretically analyzed the penetration and the following dissociation of a VAV pair in the presence of a small magnetic field H and a large dc bias current I [37]. The bound vortex-antivortex pair is confined by a potential formed by the bias current and the magnetic field.…”

“…The bound vortex-antivortex pair is confined by a potential formed by the bias current and the magnetic field. Its dissociation can be mapped into the well known problem of particle escape from a cubic potential [37]. The probability of the dissociation depends on the height of the effective potential barrier…”

Parametric amplification of vortex-antivortex pair generation in a Josephson junction

“…A similar principle has been recently used to generate Josephson vortex-antivortex pairs in a planar junction [30], where another degree of tunability was demonstrated by using a preconditioned phase imprint on the junction. Adding the fact that vortex-antivortex pairs are known to appear in Josephson junctions also under thermal and quantum fluctuations [31], and that the dynamics of such vortices under external excitations is intimately related to the properties and coherence of the emitted electromagnetic radiation from layered materials [32], it is of timely interest to see to which extent the nucleation and motion of Josephson vortex-antivortex pairs can be controlled by experimentally accessible tools.…”

Influence of Length on the Noise Delayed Switching of Long Josephson Junctions

“…It is also necessary to note that, currently, all Josephson junctions are manufactured with the use of optical and electron-beam lithography [Dorojevets, 2002;Makhlin et al, 2001], and can always be considered as distributed. Moreover macroscopic quantum phenomena in long Josephson junctions have attracted a lot of experimental and theoretical work recently [Weides et al, 2006;Mertens et al, 2006;Alfimov & Popkov, 2006;Kim et al, 2006;Fistul et al, 2003]. These junctions are characterized by one or more dimensions longer than the Josephson penetration length or depth [Barone & Paternò, 1982].…”