Beyond transcoherent states: Field states for effecting optimal coherent rotations on single or multiple qubits

Understand

Semiclassically, laser pulses can be used to implement arbitrary transformations on atomic systems; quantum mechanically, residual atom-field entanglement spoils this promise.

• Transcoherent states are field states that fix this problem in the fully quantized regime by generating perfect coherence in an atom initially in its ground or excited state.
• We extend this fully quantized paradigm in four directions: First, we introduce field states that transform an atom from its ground or excited state to any point on the Bloch sphere without residual atom-field entanglement.
• The best strong pulses for carrying out rotations by angle $\theta$ are are squeezed in photon-number variance by a factor of $\rm{sinc}\theta$.