Efficient spin polarization

A method of controlling a spin ensemble comprising:

• coupling a cavity mode of a cavity with spin states of the spin ensemble in a sample environment, the sample environment comprising a static magnetic field, the spin ensemble defining a state space comprising a plurality of angular momentum subspaces, wherein the angular momentum subspaces are defined by a total angular momentum spin operator for the spin ensemble;
• and
• generating an interaction between the cavity and the spin ensemble that increases polarization of the spin ensemble faster than the dominant thermal polarizing process affecting the spin ensemble in the sample environment,
• wherein the interaction is generated by the coupling between the spin states and the cavity mode acting independently on each of the plurality of angular momentum subspaces of the spin ensemble.