23 Jun 2023
13:15

Neuer Hörsaal

Host:
Henry Legg

Theoretical Condensed Matter Seminar

Next-Generation Qubits in Superconducting Circuits

Constantin Schrade (Niels Bohr Institute, University of Copenhagen)

Abstract:

Over the past decade, qubits encoded in superconducting circuits have emerged as a leading platform for quantum information processing, resulting in a rapidly expanding and thriving research field. However, present-day superconducting quantum processors are still highly susceptible to the effects of environmental noise, which degrades their computational performance and limits applications. As a result, developing next-generation superconducting qubits with improved protection is a major research focus to accelerate the path to a fault-tolerant quantum computer. 

In this talk, I will introduce our approach for protecting quantum information in superconducting circuits, which relies on quantum material Josephson junction realized in superconductor-semiconductor hybrid structures [1,2]. First, I will describe how such hybrid quantum materials when placed in contact with superconductors can give rise to an exotic charge-4e supercurrent and discuss approaches for experimentally detecting this coherent transport of “pairs of Cooper-pairs“ [3]. Second, I will present resulting insights in how the charge-4e supercurrent can be employed to create a protected “0-Pi“ superconducting qubit in arrays of Josephson junctions and discuss how the Josephson junction arrays can be theoretically modeled with effective spin models. Finally, I will compare the “0-Pi“ protected superconducting qubits to an alternative approach based on topological wavefunctions, the Majorana zero modes [4,5], and discuss how quantum material Josephson junctions can provide a new avenue for quantum simulation. 

[1] C. Schrade, C. M. Marcus, A. Gyenis, PRX Quantum 3, 030303 (2022)
[2] A. Maiani, M. Kjaergaard, C. Schrade, PRX Quantum 3, 030329 (2022)
[3] R. S. Souto, M. Leijnse, C. Schrade, Phys. Rev. Lett. 129 267702 (2022)
[4] C. Schrade and L. Fu, Phys. Rev. Lett 129, 227002 (2022)
[5] C. Schrade and L. Fu, Phys. Rev. Lett. 121, 267002 (2018)


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