1301.5095 (V. E. Zobov et al.)

Global phase and minimum time of quantum Fourier transform for qudits
represented by quadrupole nuclei    [PDF]

V. E. Zobov, V. P. Shauro

We demonstrate the relation between the global phase of the quantum gate and the layout of energy levels of the effective Hamiltonian, which is required for implementing the gate. The minimum time necessary to implement the quantum Fourier transform (QFT) gate for qudits represented by quadrupole nuclei with the spins I = 1 and I = 3/2 is calculated using optimal control methods. This time strongly depends on the global phase of the gate. To implement the QFT gate for a qutrit, we found the effective Hamiltonians and sequences of nonselective radiofrequency pulses separated by time intervals of free evolution for three global phase factors.

View original: http://arxiv.org/abs/1301.5095