  In a recent letter [Phy. Rev. Lett. 95, 080502 (2005)], it is claimed that
based on a new kind of quantum mechanical phase of wave function which is
neither dynamical nor geometrical a new kind of phase gate for quantum
computation is discovered. The origin of this phase is the adiabatic evolution
of a dark state. I would like to point out that these claims are questionable.
The so called new phase gate was based on a phase which was nothing new but has
been known for decades. It is something which has no physical meaning and is
not observable. It was also pointed out by [quant-ph/0509150v1] that [Phy. Rev.
Lett. 95, 080502 (2005)] was incorrect and the phase is the known geometric
phase. Here we present a totally different argument.

Quantum Physics