Thermal Entanglement in Superconducting Quantum－Interference－Device Qubits Coupled to Cavity Field

Yang Yang, Wenxing

Pan Hai-Zhong, Kuang Le-Man

We investigate thermal entanglement in a superconducting-quantum-interference-device qubit coupled to a cavity field. We show that the entanglement can be manipulated by varying temperature and an effective controlling parameter B which depends on the external field and characteristic parameters of the system. We find that there exists a critical value of the controlling parameter B c . Under a fixed temperature, increasing B can increase entanglement in the regime of B < B c , while the entanglement decreases with increasing B in the regime of B > B c .

A.‐B. A. Mohamed, Hichem Eleuch

Areeda Ayoub, Javed Akram

Wen‐Xing Yang

An alternative scheme is proposed for the generation of n-qubit W states of superconducting quantum interference devices (SQUID) in cavity QED. In this scheme, Raman coupling of two lower flux states of SQUID system is achieved via a microwave pulse and the cavity mode. Conditioned on no photon leakage from the cavity, the n-qubit W state can be generated whether the effective coupling parameters of the SQUID to cavity mode and classical microwave fields are the same or different. Our strictly numerical simulations of the time evolution of the system including decay show that the success probability of our scheme is almost unity and the interaction time is on the order of 10 −9 s. The scheme can also be used to generate the Schrödinger cat states of multi-SQUID.

Y. H. Ji, Yan Jun Hu, Yawei Yu