Quantum Correlations between Single Telecom Photons and a Multimode On-Demand Solid-State Quantum Memory

Abstract

Quantum correlations between long lived quantum memories and telecom photons that can propagate with low loss in optical fibers are an essential resource for the realization of large scale quantum information networks. Significant progress has been realized in this direction with atomic and solid state systems. Here, we demonstrate quantum correlations between a telecom photon and a multimode on-demand solid state quantum memory. This is achieved by mapping a correlated single photon onto a spin collective excitation in a Pr 3+ :Y2SiO5 crystal for a controllable time. The stored single photons are generated by cavity enhanced spontaneous parametric down conversion (SPDC) and heralded by their partner photons at telecom wavelength. These results represent the first demonstration of a multimode on-demand solid state quantum memory for external quantum states of light. They provide an important resource for quantum repeaters and pave the way for the implementation of quantum information networks with distant solid-state quantum nodes.

Memory-assisted quantum key distribution resilient against multiple-excitation effects

“…Reference [42] utilizes a low-finesse cavity to show (up to 50%) efficient and on-demand storage of strong pulses. Efficient storage using a low-finesse cavity is achieved in [43], while on-demand storage of qubits and heralded single photons are shown in [44,45], respectively. As shown in figure 7, again we simulate the key rate of the quasi-EPR scheme and find that none of the rare-earth-ion-doped crystal implementations will surpass the nomemory performance.…”

“…Specifically, we suggest memory parameters that could be obtained with realistic experimental improvements to the memories of [34][35][36][37][38][39][40][41][42][43][44][45]. We attempt to be conservative with our suggested parameters, in particular with those of efficiency and coherence time, and acknowledge that there are fundamental limitations of some parameters, e.g.…”

“…We consider the five atomic frequency comb experiments described in [41][42][43][44][45]. Europium-doped Y 2 SiO 5 crystals are employed in the investigations of [41,42] while the well-studied Pr:Y 2 SiO 5 is featured in [44,45].…”

“…The latter may differ in coherence time, efficiency, bandwidth and access time, reading and writing procedures, and operating wavelength for example. In particular, we consider a selection of state-of-the-art memories based on warm vapors at room temperature [34][35][36][37], cold ensembles of rubidium atoms [38][39][40], and cryogenically-cooled rare-earth-ion-doped crystals [41][42][43][44][45]. In the latter case, we utilize the possibility of spectral multi-mode storage [46] in such memories.…”

“…The corresponding quantum memory properties and key rates are shown in table 7 and figure 10, respectively. We employ the 151 Eu:Y 2 SiO 5 memory of [41], except that we assume perfect dynamical decoupling is in use to achieve a coherence time that is entirely limited by the ground-level homogeneous broadening (Eu+DD), and we employ the Pr:Y 2 SiO 5 crystal of [44,45] (Pr+DD) in a similar way. Even with perfect efficiency, we find that neither of the quantum memories overcome the bound, mainly due to their limited bandwidth in comparison to the Raman quantum memories.…”