Figure 1

Overview of the experiment. (a) and (b) The atomic level schemes of ${}^{87}\mathrm{Rb}$ with a weak ($B_0=0.59\mathrm{G}$) and a moderate ($B_0=13.5\mathrm{G}$) magnetic field, respectively. ${\sigma }^{+}$ and ${\sigma }^{-}$ are right-and left-polarized signal light fields, respectively. (c) The experimental setup. Acronyms are defined in the text except for neutral density filters (NDF) and the Glan-laser polarizer (GLP).Reuse & Permissions

Figure 2

Measured retrieval efficiencies as the function of the storage time $t$ for the ${\sigma }^{+}$-polarized (a) and ${\sigma }^{-}$-polarized (b) signal fields. Black square and red circular points are the experimental data obtained for $B_0=13.5$ and $B_0=0.59\mathrm{G}$, respectively. The blue solid lines $I$ in (a) and $I^{\prime }$ in (b) are the fittings to the experimental data (black square points) according to $R_e^{\pm }(t)=R_{e0}{e}^{-t/{\tau }_1}$, respectively, which yields $R_{e0}=8.3\%$, ${\tau }_1=1.6\mathrm{ms}$. The fitting result of 1.6 ms is close to the calculated value ${\tau }_1={\tau }_D{\tau }_1^z/({\tau }_D+{\tau }_1^z)\approx 1.9\mathrm{ms}$, where ${\tau }_D\approx 3.3\mathrm{ms}$ and ${\tau }_1^z\approx 4.6\mathrm{ms}$ are the evaluated results in the text. The green lines $II$ in (a) and $I{I}^{\prime }$ in (b) are the fittings to the experimental data (red circular points) according to theoretical models in which the imperfect atomic preparation has been taken into account (see the Supplemental Material [35]).Reuse & Permissions

Figure 3

Quantum process fidelity as the function of storage time $t$. The data are fitted by Eq. (3), with the measured total detection efficiency ${\eta }_d\approx 0.19$ and background noise $N=2.2\times {10}^{-4}$. The retrieval efficiencies $R_e^{\pm }(t)=0.083e^{-t/1.6}$ are obtained from both fitting curves $I$ and $I^{\prime }$ in Fig. 2. The fitting yields the $e^{-1}$ dephasing time of ${\sigma }_{\gamma }=14\mathrm{ms}$.Reuse & Permissions