Ab initio study of optimal control of ammonia molecular vibrational wavepackets: Towards molecular quantum computing

Analytic approach for controlling quantum states in complex systems

“…The existence of an optimal field is proved by optimal control theory (OCT) [24], which is a powerful tool to obtain an optimal field and has been studied for various dynamical systems [25,26]. For the purpose of steering quantum states, many numerical schemes with monotonically convergent algorithms [1,27,28] have been developed based on OCT.…”

Quantum computing using molecular electronic and vibrational states

“…Next, we summarize the merits and demerits for vibrational-rotational, vibrational-vibrational, and electronicvibrational combinations by comparing the present results and the previous ones done by our group [11][12][13] and other authors [7]. The merit of the vibrational-rotational qubits is that the entanglement can be created by laser pulses so that the entangling strength can be controlled by adjusting the incident laser pulses, while the demerit is that in order to create and perform the quantum algorithms we need to shine both the IR and the microwave laser pulses at the same time which may be difficult to realize experimentally [12,13].…”

“…In addition, it was revealed that the selection rule of the rotational transition limits the efficiency of the performance of the quantum algorithm [12]. On the other hand, the merit of the vibrational-vibrational qubits is that we need to shine only the IR pulses which is easy to realize experimentally [7,11]. However, the demerit is that the entangling strength of two vibrational modes cannot be controlled or is constant so that the shape of the laser pulses may be limited.…”

“…To proceed further, we have theoretically shown that it is possible to realize the quantum computing and generate entanglement by using not only two different vibrational modes [11] but also the vibrational and rotational modes in a molecule [12,13]. In these studies, we have shown that the entanglement and arbitrary superposition states can be generated by consecutive three chirped pulses [13] and that the Deutsch-Jozsa algorithm can be realized by laser pulses tailored by optimal control theory (OCT) [12].…”

The operations of quantum logic gates with pure and mixed initial states

“…[15][16][17][18][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] The Deutsch-Jozsa algorithm is one of the elementary algorithms in quantum computation. This algorithm was simulated theoretically using vibrational states of acetylene 18 and electronic excited states of iodine.…”