The Fourier components of X (t) and P (t) are simple, and more so if they are combined into the quantities A ( t ) = X ( t ) + i P ( t ) = 2 E e − − i t , A † † ( t ) = X ( t ) − − i P ( t ) = 2 E e i t . Both A and A have only a single frequency, and X and P can be recovered from their sum and difference.