The aim of this paper is to design a current source obtained as a representation of p information symbols $$\{I_k\}$${Ik} so that the electromagnetic (EM) field generated interacts with a quantum atomic system producing after a fixed duration T a unitary gate U(T) that is as close as possible to a given unitary gate $$U_g$$Ug. The design procedure involves calculating the EM field produced by $$\{I_k\}$${Ik} and hence the perturbing Hamiltonian produced by $$\{I_k\}$${Ik} finally resulting in the evolution operator produced by $$\{I_k\}$${Ik} up to cubic order based on the Dyson series expansion. The gate error energy is thus obtained as a cubic polynomial in $$\{I_k\}$${Ik} which is minimized using gravitational search algorithm. The signal to noise ratio (SNR) in the designed gate is higher as compared to that using quadratic Dyson series expansion. The SNR is calculated as the ratio of the Frobenius norm square of the desired gate to that of the desired gate error.
['Navneet Sharma', 'Tarun Kumar Rawat', 'Harish Parthasarathy', 'Kumar Gautam']
Realization of a quantum gate using gravitational search algorithm by perturbing three-dimensional harmonic oscillator with an electromagnetic field