Multiplet supercurrent in Josephson tunneling circuits

Abstract

The multi-terminal Josephson effect allows DC supercurrent to flow at finite commensurate voltages. Existing proposals to realize this effect rely on nonlocal Andreev processes in superconductor-normal-superconductor junctions. However, this approach requires precise control over microscopic states and is obscured by dissipative current. We show that standard tunnel Josephson circuits also support multiplet supercurrent mediated only by local tunneling processes. Furthermore, we observe that the supercurrents persist even in the high charging energy regime in which only sequential Cooper transfers are allowed. Finally, we demonstrate that the multiplet supercurrent in these circuits has a quantum geometric component that is distinguishable from the well-known adiabatic contribution.

Dynamical Stabilization of Multiplet Supercurrents in Multi-terminal Josephson Junctions

“…In this text, we show conclusively that multiplet resonances can also emerge as a consequence of the three terminal circuit model, similar to the theoretical prediction of Ref. [17]. The supercurrent appears due to the correlated phase dynamics at values that correspond to the multiplet condition nV1 = −mV2 of applied bias.…”

“…More specifically, the robust classical 2φ periodicity of the multiplet resonances may be useful in developing cos 2φ qubits [17,34,35]. In this case, coherence could be generated using flux biasing with superconducting loops, which have been used to probe topological states in diffusive multiterminal junctions [8,9].…”

“…These multiplets have been an area of intense theoretical [10-13, 17, 24] and experimental [14][15][16] study as they show promise to provide insights into Floquet dynamical systems [10][11][12][13]16]. However, it has recently been found that quartets may classically emerge as a consequence of the mixing of strictly sinusoidal current phase relations (CPR) [17]. Here, we demonstrate classical quartets in the case of a three terminal graphene Josephson junction (Figure 1a), a three-terminal Josephson junction analogue (Figures 2,3), and simulations of the multi-terminal circuit (Figures 4,5).…”

Dynamical Stabilization of Multiplet Supercurrents in Multiterminal Josephson Junctions

“…These multiplets have been an area of intense theoretical − and experimental − study as they require the multicontact phase coherent trajectories necessary to realize synthetic topological states predicted in these devices. − Further, the multiplets themselves show promise to provide insights into Floquet dynamical systems. ,− However, it has been proposed that quartets may classically emerge as a consequence of the mixing of strictly sinusoidal current phase relations (CPR) . Here, we demonstrate classical quartets in the case of a three-terminal graphene JJ (Figure a), a three-terminal JJ analogue (Figures ,), and simulations of the multiterminal circuit (Figures and ).…”

“…However, the π – 0 transition observed in that work cannot be explained by our model, and may thus be conclusive evidence of the observation of quartet states. The robust classical 2φ periodicity observed along the quartet resonance may be useful in developing new quantum devices such as cos 2φ qubits, ,, using flux loops , to control the trajectory in phase space.…”