Robust Hadamard gate for optical and ion trap holonomic quantum   computers
  We consider one possible implementation of Hadamard gate for optical and ion trap holonomic quantum computers. The expression for its fidelity determining the gate stability with respect to the errors in the single-mode squeezing parameter control is analytically derived. We demonstrate by means of this expression the cancellation of the squeezing control errors up to the fourth order on their magnitude. 
V.I. Kuvshinov, A.V. Kuzmin