Abstract:
A coherent technique for the control of photon propagation in optically
thick media and its application for quantum memories is discussed. Raman
adiabatic passage with an externally controlled Stokes field can be used to transfer
the quantum state of a light pulse (“flying” qubit) to a collective spin-excitation
(stationary qubit) and thereby slow down its propagation velocity to zero. The
process is reversible and has a potential fidelity of unity without the necessity for
strongly coupling resonators. A simple quasi-particle picture (dark-state polariton)
of the transfer is presented. The analytic theory is supplemented with exact numerical
solutions. Finally the influence of decoherence mechanisms on collective storage
states, which are N-particle entangled states, is analyzed.
