Reversible storage of a weak light pulse in a thermal atomic medium

Reversible storage of photon entanglement in thermal atomic ensembles

“…Solid curves 1-3 describe the timedependent photon entanglement and dashed curves 4-6 the corresponding atomic ensemble entanglement, respectively, for the atomic velocity distribution width D∕γ: 0.0, 10.0 and 20.0. There is a common feature of the curves similar to that seen in a conventional photon storage scheme based on EIT [14][15][16]22]; that is, the photon entanglement is mapped into the atomic ensembles as the control field is switched off and is retrieved subsequently after the control field is switched on. This process, according to the DS description (6), corresponds to jΨθ; θ 0 i θθ 0 0.0 ↔jΨθ; θ 0 i θθ 0 π∕2 or 1∕ 2 p j01i e iϕ j10ijḡḡij θθ 0 0.0 ↔1∕ 2 p jḡsi jsḡij00i j θθ 0 π∕2 via stimulated Raman adiabatic passage.…”

“…The density matrix approach becomes an effective way to solve the problem at hand as the decoherent effect resulting from the environment action is taken into consideration [16]. If we denoteρ αβ t; v; m; n (m, n 0; 1) as the v-dependent collective density operator for one of two subsystems and the related density element as ρ αβ t; v; m; n c α t; v; mc β t; v; n, then the elements for the two atomic ensembles and for the two photon modes can be written as…”

Electromagnetically induced transparency of the medium composed of atoms in thermal motion

“…where ρ ge (p − hk 1 , p) = 1 N N j =1 g j , p j − hk 1 e j , p j is the newly introduced p-dependent collective atomic density operator [22]. To obtain equation ( 1), we have sorted the atoms into groups according to their momenta; thus the sequence of the two summations over atomic number j and momentum p j can be exchanged and then subscript j is omitted.…”

“…We assume that the atomic assemble has a temperature at which both the atomic internal and translational degrees of freedom can be treated quantum mechanically. Thus, families of collective atomic states, which are closed with respect to absorption and stimulated emission [21], and momentumdependent collective atomic density operators [22] can be introduced, respectively. The initial atomic thermal motion with a velocity distribution is modelled by the Gaussian function.…”

Storage and Retrieval of a Weak Optical Signal Improved by Spontaneously Generated Coherence in an Atomic Assemble

“…is introduced as the p-dependent collective atomic density operator. [20] To obtain the last equation in Eq. ( 1) we have sorted the atoms into groups according to their momenta, thus the sequence of the two summations over atomic number j and momentum p j can be exchanged and then subscript j is omitted.…”