Creation of coherent superpositions of Raman qubits by using dissipation

We show how to create coherent superpositions between two ground states of Lamda quantum system of three states, among which the middle one decays. The idea is to deplete the population of the bright state formed by the two ground states via the population loss channel. The remaining population is trapped in the dark states, which can be designed to be equal to any desired coherent superposition of the ground states. The present concept is an alternative to the slow adiabatic creation of coherent superpositions and may therefore be realized over short times, especially in the case where the middle state has a short life span. However, the price we pay for the fast evolution is associated with an overall 50% population losses. This issue can be removed in an experiment by using post-selection.