Superposition of nuclear states in multi-lambda systems using x-ray laser pulses

Nuclear-state population transfer in the multi-lambda systems with N = 5 that interact with four X-ray laser pulses are investigated theoretically. By using the coincident pulses and stimulated Raman adiabatic passage (STIRAP) techniques, the population transfer from one initially populated ground state to an arbitrary coherent superposition of other ground states. Since the frequency of currently available X-ray lasers is lower than the gamma rays, in this method, X-ray laser pulses with different frequencies are interacting with the accelerated nuclei. We employ the Morris-Shore (MS) transformation to reduce the five-states system to two separate three-state and two-state linkage. The required laser intensities were calculated, which satisfy the conditions of coincident pulses and multi-lambda STIRAP techniques. Considering the spontaneous emission from excited states, the master equation has to be used for numerical study, and it is shown that an arbitrary superposition of final ground states can be obtained. Also, it is observed that by increasing the number of coincident pulses, the population of ground states gets closer to the ideal situation.

Using deep learning for digitally controlled STIRAP

Stimulated Raman Adiabatic Passage (STIRAP) is a technique for preparing atoms and molecules in an arbitrary preselected coherent superposition of quantum states, ordinarily controlled by Gaussian laser pulses. We search novel pulse sequences by exploiting deep reinforcement learning algorithms in order to achieve fast and flexible solutions for integer and fractional STIRAP. By using the robustness of the PPO algorithm, we impose the agent to exploit only digital pulses corresponding to on/off states of the control radiation instead of continuous amplitudes. Such method allows to adapt to detuning of the energy levels and disturbances such as dephasing.