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Cooper-Pair Splitters as Circuit Elements for Realizing Topological Superconductors

Guilherme Delfino1, Dmitry Green1,2, Saulius Vaitiekėnas3, Charles M. Marcus3,4,5, and Claudio Chamon1,*

  • *Contact author: chamon@bu.edu
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PRX Quantum 6, 030318 – Published 31 July, 2025

DOI: https://doi.org/10.1103/3c6m-x28w

Abstract

Advances in materials and fabrication of superconducting devices allows the exploration of novel quantum effects in synthetic superconducting systems beyond conventional Josephson-junction arrays. As an example, we introduce a new circuit element, the Y splitter, a superconducting loop with three leads and three Josephson junctions, smaller or comparable in size to the superconducting coherence length of the material. By tuning magnetic flux through an array of Y splitters, Cooper-pair transport can be made to interfere destructively, while spatially separated split Cooper pairs propagate coherently. We consider an array of Y splitters connected in a two-dimensional star [Archimedean (3,122)] geometry, deformable into the kagome lattice, and find a rich phase diagram that includes topological superconducting phases with Chern numbers ±2. Experimental realization appears feasible.

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Popular Summary

The ability of superconductors to carry electricity without loss is key to building circuits that follow the laws of quantum mechanics, making them leading contenders for quantum computing architectures. To date, the main components of such circuits are capacitors, inductors, and Josephson junctions. While superconductivity arises from electrons moving in pairs, this pairing is typically hidden in the theoretical analysis of superconducting circuits and only becomes relevant when pairs break apart, which is often regarded as an undesirable feature that can disrupt the quantum behavior of the circuit.

What if, instead, one could harness the pair breaking? This paper introduces a new component for superconducting circuits: the Y splitter. It consists of a superconducting ring with three arms, each connected by Josephson junctions. The Y splitter is designed to split Cooper pairs—the bound electrons responsible for superconductivity—and recombine them in a controlled way that spreads quantum correlations across the circuit. By combining many Y splitters into a network, the authors show how to create the conditions necessary for topological superconductivity, a phase of matter with potential applications in quantum information.

The work combines theory with realistic circuit design, setting a path toward experimental realization. This approach introduces a new superconducting circuit element to the existing toolkit for constructing topological quantum states.

Article Text

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PRX Quantum 6, 030318– Published 31 July, 2025
  • Received 4 October 2024
  • Revised 3 May 2025
  • Accepted 5 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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