Quantum-state transfer between fields and atoms in electromagnetically induced transparency

We show that a quasiperfect quantum-state transfer between an atomic ensemble and fields in an optical cavity can be achieved in electromagnetically induced transparency (EIT). A squeezed vacuum field state can be mapped onto the long-lived atomic spin associated to the ground-state sublevels of the $\Lambda$-type atoms considered. The EIT on-resonance situation show interesting similarities with the Raman off-resonant configuration. We then show how to transfer the atomic squeezing back to the field exiting the cavity, thus realizing a quantum memory–type operation.

Figure 1

Three-level system in a $\Lambda$ configuration.

Figure 2

(Color online) Transfer efficiency versus $\overline{\Delta }$ for ${\gamma }_0=0$ (plain) and ${\gamma }_0=\gamma ∕1000$ (dash) $\left(C=100,{\gamma }_E=15\right)$.

Figure 3

(Color online) EIT transfer efficiency versus EIT pumping rate: analytical (23) (plain), low frequency approximation (11) (dots), and lossless system (24) (dashed). The three regimes are I $\left(\Gamma ⪡{\gamma }_0\right)$, II $\left({\gamma }_0⪡\Gamma ⪡\gamma ,\kappa \right)$, and III $\left(\Gamma \gtrsim \gamma ,\kappa \right)$. Parameters: $C=100$, $\sigma =1∕1000$, $\rho =1∕2$. The optimal pumping rate is then ${\gamma }_E^{*}\simeq 15$.

Figure 4

(Color online) Transfer efficiency versus $\tilde{\delta }∕{\gamma }_0$ in EIT (plain) and Raman (dash) schemes. Parameters: $C=100$, $\sigma =1∕1000$, $e^{-2r}=0.5$. With these values, ${\Gamma }_E$ and ${\Gamma }_R$ are chosen so that, in both cases, ${\tilde{\gamma }}_0\simeq 75{\gamma }_0$.