  I describe the use of techniques based on composite rotations to combat
systematic errors in controlled phase gates, which form the basis of two qubit
quantum logic gates. Although developed and described within the context of
Nuclear Magnetic Resonanace (NMR) quantum computing these sequences should be
applicable to any implementation of quantum computation based on Ising
couplings. In combination with existing single qubit gates this provides a
universal set of robust quantum logic gates.
