A multi-qubit system for a scalable adiabatic quantum evolution

We study the Hamiltonian of a system of inductively coupled flux qubits, which has been theoretically proposed for adiabatic quantum computation to handle NP problems. We study the evolution of a basic structure consisting of three coupled rf-SQUIDs upon tuning the external flux bias, and we show that the adiabatic nature of the evolution is guaranteed by the presence of the single-SQUID gap. We further propose an experiment to study the problem of scaling up the number of coupled qubits guaranteeing the adiabatic nature of the process. © 2005 Elsevier B.V. All rights reserved.