Ultralong-distance quantum correlations in three-terminal Josephson junctions

Abstract

In these studies, the distance between the contacts is limited by the zero-energy superconducting coherence length. Here, we demonstrate nonlocality and quantum correlations in voltage-biased three-terminal Josephson junctions over the ultralong distance that exceeds the superconducting coherence length by orders of magnitude. The effect relies on the interplay between the time-periodic Floquet-Josephson dynamics, Cooper pair splitting, and long-range coupling similar to the two-terminal Tomasch effect. We find crossover between the "Floquet-Andreev quartets" (if the spatial separation is smaller than the superconducting coherence length) and the "ultralong-distance Floquet-Tomasch clusters of Cooper pairs" if the separation exceeds the superconducting coherence length, possibly reaching the same 30 μm as in the Tomasch experiments. The effect can be detected with DC-transport and zero-frequency quantum current-noise cross-correlation experiments, and it can be used for fundamental studies of superconducting quasiparticle quantum coherence in the circuits of quantum engineering.

Quantum interferometer for quartets in superconducting three-terminal Josephson junctions

“…Multiterminal Josephson junctions (MTJs) [1][2][3][4] appear as a very fertile evolution in the field of superconductivity. While unbiased MTJs offer prospects as platforms for controllable topological properties [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], biased MTJs reveal new channels for both superconducting phase-sensitive and quantum mechanical DC currents, as predicted by theory [22,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] and confirmed in experiments [43][44][45][46][47]…”

Josephson tunnel junction arrays and Andreev weak links: what’s the difference?

“…[38][39][40][41][42] Explanations based on Andreev levels that are connected to more than one terminal were proposed. 43,44 Classical and quantum multiterminal SIS circuits should also exhibit multiplet supercurrent, 45 which we briefly motivate.…”