Stabilizing Majorana bound states in artificial Kitaev chains through reservoir couplings

• Grant number: 25/18261-2
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: February 01, 2026
• End date: January 31, 2029
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Miled Hassan Youssef Moussa
• Grantee: Rodrigo de Abreu Dourado
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 24/13689-1 - Building the Quantum Mechanics of Time-Dependent Pseudo-Hermitian Hamiltonians., AP.R

Abstract

The main predicaments to the operation of quantum computers are quantum noise and the decoherence of quantum states due to the coupling of qubits to the environment. A theorized route to achieving fault-tolerant quantum computation is the implementation of topological qubits with Majorana Bound States (MBSs), which would be, in principle, robust against local noise and decoherence-free. The most promising experimental approach to building Majorana qubits involves engineering artificial Kitaev chains using short arrays of semiconducting-superconducting quantum dots. However, MBSs in this context exist only at discrete points in parameter space, making the practical implementation far less robust than the theorized topological model. This project aims to leverage the couplings of the system to reservoirs to enhance the characteristics of artificial Kitaev chains and Majorana qubits, focusing on robustness against parameter fluctuation, excitation gap, and dephasing times. Our primary approach will involve the non-Hermitian regime, accessed by integrating out the reservoir's degrees of freedom to obtain effective non-Hermitian Hamiltonians. From there, the system can be driven to Exceptional Points (EPs), i.e., bifurcations in the complex plane where intriguing phenomena arise, such as the real part of the energy of excitations being pinned to zero and an increase in the lifetime of quasiparticles. Using this framework, we will apply concepts from quantum optics where dissipative interacting systems can yield decoherence-free subspaces, protecting quantum states from the injection of noise from the reservoirs. Further, we will investigate the behavior of MBSs in minimal (2-site) artificial Kitaev chains in the open system regime, aiming to improve their stability through EPs. Finally, a time-dependent approach will allow us to examine the influence of reservoirs on the manipulation of MBSs, with a focus on decoherence times, as well as the implementation of braiding and fusion protocols in the non-Hermitian limit. The realization of artificial Kitaev chains is currently undergoing intense development, and our proposal to exploit the coupling to reservoirs to improve their properties might guide future experimental efforts in the area. (AU)