User:Jitenphy

Stimulated Raman adiabatic passage (STIRAP):
STIRAP process permits us to transfer the population between two applicable quantum states via at least  two coherent  electromagnetic  (light) pulses. These light pulses drive the transitions of the three level  Ʌ atom or multilevel system.

Population transfer in three level Ʌ atom :
Let us consider the description of three level Ʌ atom having ground state $$|g_1\rangle $$ and $$|g_2\rangle $$  ( for simplicity consider the energy of both ground states are same ) and excited state $$|e\rangle $$ respectively.Suppose in the begining the the total population is in the ground state $$|g_1\rangle $$. Here the logic for transformation of the population from ground state $$|g_1\rangle $$ to $$|g_2\rangle $$ is that initially the unpopulated states $$|g_2\rangle $$ and $$|e\rangle $$ couple, afterward superposition of state $$|g_2\rangle $$ and $$|e\rangle $$ couple to the state $$|g_1\rangle $$.Thereby a state is form that permit to transform the population into state $$|g_2\rangle $$ with out populating the excited state $$|e\rangle $$.This process of transform the population with out populating the excited state is called the stimulated Raman adiabatic passage.