Optimal light storage with full pulse-shape control

We experimentally demonstrate optimal storage and retrieval of light pulses of arbitrary shape in atomic ensembles. By shaping auxiliary control pulses, we attain efficiencies approaching the fundamental limit and achieve precise retrieval into any predetermined temporal profile. Our techniques, demonstrated in warm Rb vapor, are applicable to a wide range of systems and protocols. As an example, we present their potential application to the creation of optical time-bin qubits and to controlled partial retrieval.

Figure 1

(Color online) (a) Schematic of the three-level $\Lambda$ interaction scheme. Control (b) and signal (c) fields in pulse-shape-preserving storage of a “positive-ramp” pulse using a calculated optimal control field envelope $\Omega \left(t\right)$. During the writing stage $(t<0)$, the input pulse ${\mathcal{E}}_{\mathrm{in}}\left(t\right)$ is mapped onto the optimal spin wave $S\left(z\right)$ [inset in (b)], while a fraction of the pulse escapes the cell (leakage). After a storage time $\tau$, the spin wave $S\left(z\right)$ is mapped into an output signal pulse ${\mathcal{E}}_{\mathrm{out}}\left(t\right)$ during the retrieval stage. The dashed blue line in (c) shows the target output pulse shape.

Figure 2

(Color online) An input Gaussian pulse was optimally stored and retrieved either into its original pulse shape (a) or into a ramp pulse shape (b). Similarly, the incoming ramp pulse was optimally stored and retrieved into a Gaussian (c) or into an identical ramp (d). Input and output signal pulses are shown as dotted and solid black lines, respectively, while the optimal control fields are shown as solid red lines.

Figure 3

(Color online) Examples of storage of signal input pulses with Gaussian and triangular envelopes, followed by retrieval in a linear combination of two time-resolved Gaussian pulse shapes $g_1\left(t\right)$ and $g_2\left(t\right)$. Input and output signal fields are shown as dotted and solid black lines, respectively. Dashed blue lines show the target envelopes.