Eur. Phys. J. D 61, 499-505 (2011)
https://doi.org/10.1140/epjd/e2010-00258-5

Implementing multi-qubit entanglement of two-level systems inside a superconducting phase qubit

¹ Laboratory of Quantum Information Technology, ICMP and SPTE, South China Normal University, Guangzhou, P.R. China
² Department of Physics and Electronic Engineering, Hefei Normal University, Hefei, P.R. China
³ Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
⁴ National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, P.R. China

Corresponding author: ^a longbaoyu@yahoo.com.cn

Received: 12 May 2010
Revised: 22 August 2010
Published online: 8 October 2010

Abstract

The interaction between a superconducting phase qubit and the two-level systems located inside the Josephson tunnel barrier is described by the XY model, which is naturally used to implement the i-SWAP gate. With this gate, we propose a scheme to efficiently generate multi-qubit entangled states of such two-level systems, including multipartite W state and cluster states. In particular, it is found that, with the help of the phase qubit, the entanglement witness can be used to efficiently detect the produced multi-qubit entangled states.