Microwave and spin transfer torque driven coherent control in ferromagnets

Coherent Control is key to quantum technologies. At its heart stands the non-equilibrium energy exchange between the electromagnetic radiation and the material system. Recently, interest has grown in this regime in ferromagnets because of the ability to combine it with spintronics for the purpose of fundamental spin transport research in solid state devices, information processing, and potentially also future quantum bit (Qubit) applications. In this work we address the theoretical grounds of coherent manipulation in practical ferromagnetic systems. We study the interaction as a result of driving electromagnetic radiation and static spin transfer torques (STT) arising from spin polarized currents. We discuss the conditions for obtaining Rabi oscillations and show that the anisotropy field acts as an additional oscillatory driving field. We discuss the Gilbert losses in the context of coherence decay rates and show that it is possible to control the coherence times by application of a static STT. The possibility of using an oscillatory STT as a driving field to replace the electromagnetic radiation used in the manipulation of Qubit is considered. Such a replacement will allow to scale down the Qubits, as well as to increase their reliability by reducing the cross-talk between neighboring Qubits.