Consider the matrix U. Find the value of the real number λ such that U = M/λ is a unitary matrix. Describe the action of this gate on a qubit.
A) λ = 1, U is an identity gate
B) λ = 2, U is a Pauli-X gate
C) λ = 0.5, U is a Hadamard gate
D) λ = -1, U is a phase gate