A Realization Scheme for Half-adder at Room Temperature by Two Transition Pulses in NMR Quantum Information Processing

In quantum information processing, realization of 3-qubit quantum operation is challenging especially when multiple logic operations are required to build non-trivial quantum circuits. Quantum half-adder is a 3-qubit circuit and in this work, a simple realization scheme for quantum half-adder operation is proposed. The 3-qubit quantum circuit is composed of a Toffoli operation and a controlled-NOT operation in succession. These two operations are shown to be achievable only by two transition pulses in nuclear magnetic resonance based quantum computing at room temperature. In our proposed scheme, three weakly coupled spin 1/2 nuclei of a molecule serve as three qubits. The time-independent internal Hamiltonian of the system allows us to obtain the desired multi-qubit operation. The simple structure of the spin 1/2 systems of our scheme make it easy to be implemented in experiments. Simulation on fidelity estimation reveals that more than 96% fidelity is achievable in worst case scenario