“Stopping” of light and quantum memories for photons

Abstract

Summary. -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.

Control with EIT: High Energy Charged Particle Detection

“…An explicit evaluation of the integral in terms of complex error functions can be done in the far-field limit by approximating k ⊥ by a piecewise function composed of parabolas. As shown in Figure 5, we consider the local quadratic best fit in the region and expand it about a central frequency, 2 . We evaluate the radial component of the E-field which has a Hankel function of first type with order 1.…”

“…Theoretical studies have opened up several applications including generation of non-classical atomic ensembles, high-resolution spectroscopy and reversible quantum memories in optical systems. A proposed technique by Fleischhauer and Mewes to greatly increase storage time for use in quantum memory is in adiabatically reducing the control field's strength to bring the light to a halt, effectively mapping the light's quantum state to the atomic spin ensemble and then achieve reconstruction through restoring the control field's strength [1,2]. An experiment realization of this protocol in a laser-cooled ensemble of a cloud of Rb-87 atoms in a magneto-optical trap achieved a favourable result of 0.036 storage efficiency for a transport distance of 1.26 mm (1/e size of the cloud) for a lifetime of 2.6 ms [3].…”