We further study the security of the quantum bit commitment (QBC) protocol we previously proposed [Phys. Rev. A 74, 022332 (2006).], by analyzing the reduced density matrix \rho_{ b}^{ B} which describes the quantum state at Bob's side corresponding to Alice's committed bit b. It is shown that Alice will find \rho_{ 0}^{ B}\perp \rho_{ 1}^{ B} while the protocol remains concealing to Bob. On the contrary, the existing no-go theorem of unconditionally secure QBC is based on the condition \rho_{ 0}^{ B}\simeq \rho_{ 1}^{ B}. Thus the specific cheating strategy proposed in the no-go theorem does not necessarily applies to our protocol.
Categories: quant-ph