Single qubit quantum secret sharing with improved security

Analyzing carefully an experimentally feasible non-entangled single qubit quantum secretsharing protocol and its modified version [Phys. Rev. Lett. 95, 230505 (2005); ibid.98, 028902 (2007)], it is found that both versions are insecure against coherent attacksthough the original idea is so remarkable. To overcome this fatal flaw, here we proposea protocol with a distinct security checking strategy, which still involves single qubitoperations only, making it possible to achieve better security of quantum secret sharingwith current technology.