“…In particular, it has been reported that the phase‐GHZ state with a π/4 phase can be useful for magic‐state distillation. [
30 ] We can prepare the desired phase‐GHZ state
with phase θ by adjusting the local phase of one of the four photons. In this procedure,
can be expressed as the unitary transformation of the
state, with the zero‐phase expressed in Equation (3), as follows:
…”