Qubit-loss-free fusion of atomic W states via photonic detection

Abstract

In this paper, we propose two new qubit-loss-free (QLF) fusion schemes for W states in cavity QED system. Resonant interactions between atoms and single cavity mode constitute the main fusion mechanism, with which atomic $$|W_{n+m}\rangle $$ and $$|W_{n+m+q}\rangle $$ states can be generated, respectively, from a $$|W_{n}\rangle $$ and a $$|W_{m}\rangle $$ and from a $$|W_{n}\rangle $$ , a $$|W_{m}\rangle $$ and a $$|W_{q}\rangle $$ , by detecting the cavity mode. The QLF property of the schemes makes them more efficient and simpler than the currently existing ones, and fewer intermediate steps and memory resources are required for generating a target large-scale W state. Furthermore, the fusion of atomic states can be realized via the detection on cavity mode rather than the much complicated atomic detection, which makes our schemes feasible. In addition, the analyses of the optimal resource cost and the experimental feasibility indicate that the present schemes are simple and efficient, and maybe implementable within the current experimental techniques.