Macroscopic Greenberger-Horne-Zeilinger and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>W</mml:mi></mml:math>states in flux qubits

Abstract

We investigate two types of genuine three-qubit entanglement, known as the Greenberger-Horne-Zeilinger (GHZ) and $W$ states, in a macroscopic quantum system. Superconducting flux qubits are theoretically considered in order to generate such states. A phase coupling is proposed to offer enough strength of interactions between qubits. While an excited state can be the $W$ state, the GHZ state is formed at the ground state of the three flux qubits. The GHZ and $W$ states are shown to be robust against external flux fluctuations for feasible experimental realizations.