Robust creation of entangled states of two coupled flux qubits via dynamic control of the transition frequencies

TL;DR

This paper presents robust methods for creating entangled Bell states in two superconducting flux qubits by dynamically controlling their transition frequencies, achieving high fidelity despite decoherence.

Contribution

It introduces schemes using continuous-wave control and Stark-chirped adiabatic passages with dynamic frequency tuning for robust entanglement creation.

Findings

Successful creation of Bell states with high fidelity

Dynamic control improves robustness against decoherence

Comparison of different control schemes

Abstract

Coherent control and the creation of entangled states are discussed in a system of two superconducting flux qubits interacting with each other through their mutual inductance and identically coupling to a reservoir of harmonic oscillators. We present different schemes using continuous-wave control fields or Stark-chirped rapid adiabatic passages, both of which rely on a dynamic control of the qubit transition frequencies via the external bias flux in order to maximize the fidelity of the target states. For comparison, also special area pulse schemes are discussed. The qubits are operated around the optimum point, and decoherence is modelled via a bath of harmonic oscillators. As our main result, we achieve controlled robust creation of different Bell states consisting of the collective ground and excited state of the two-qubit system.