Quantum memory for images: A quantum hologram

Matter-light quantum interface and quantum memory for light are important ingredients of quantum information protocols, such as quantum networks, distributed quantum computation, etc. [P. Zoller et al., Eur. Phys. J. D 36, 203 (2005)]. In this paper we present a spatially multimode scheme for quantum memory for light, which we call a quantum hologram. Our approach uses a multiatom ensemble which has been shown to be efficient for a single spatial mode quantum memory. Due to the multiatom nature of the ensemble and to the optical parallelism it is capable of storing many spatial modes, a feature critical for the present proposal. A quantum hologram with the fidelity exceeding that of classical hologram will be able to store quantum features of an image, such as multimode superposition and entangled quantum states, something that a standard hologram is unable to achieve.

Figure 1

The scheme of the write stage of the quantum hologram.

Figure 2

Covariance matrix diagonal element for one pixel (the bold and hair lines—with and without phase correction of squeezing by means of a thin lens). Here $\psi (0,0)=\pi ∕2$, $\exp \left[r\right(0,0\left)\right]=3$.

Figure 3

Average fidelity per pixel for the initial coherent state (a) and the perfect squeezed state (b) of the collective atomic spin. The parameters of light squeezing are the same as in Fig. 2.