Quantum storage of entangled photons at telecom wavelengths in a crystal

Abstract

The quantum internet -- in synergy with the internet that we use today -- promises an enabling platform for next-generation information processing, including exponentially speed-up distributed computation, secure communication, and high-precision metrology. The key ingredients for realizing such a global network are the distribution and storage of quantum entanglement. As ground-based quantum networks are likely to be based on existing fiber networks, telecom-wavelength entangled photons and corresponding quantum memories are of central interest. Recently, ${}^{167}\mathrm{E}{\mathrm{r}}^{3+}$ ions have been identified as a promising candidate for an efficient, broadband quantum memory at telecom wavelength. However, to date, no storage of entangled photons, the crucial step of quantum memory using these promising ions, ${}^{167}\mathrm{E}{\mathrm{r}}^{3+}$, has been reported. Here, we demonstrate the storage and recall of the entangled state of two telecom photons generated from an integrated photonic chip based on a silicon nitride micro-ring resonator. Combining the natural narrow linewidth of the entangled photons and long storage time of ${}^{167}\mathrm{E}{\mathrm{r}}^{3+}$ ions, we achieve storage time of 1.936 $\mu$s, more than 387 times longer than in previous works. Successful storage of entanglement in the crystal is certified by a violation of an entanglement witness with more than 23 standard deviations (-0.234 $\pm$ 0.010) at 1.936 $\mu$s storage time. These results pave the way for realizing quantum networks based on solid-state devices.

We have improved the storage time of quantum entanglement to over 1.9 $\mu$s with a efficiency of about 2%, using partial nuclear spin polarization as well as better frequency locking for the laser system. We have also enhanced the coherence of signal photons, which are generated from an entangled photon-pair source based on an integrated microring resonator with a quality factor exceeding 10^6

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• Recent advances in high-dimensional mode-locked quantum frequency combs
• Quantum networks using rare-earth ions
• Postselection-Free Cavity-Enhanced Narrow-Band Orbital Angular Momentum Entangled Photon Source
• Quantum Teleportation from Telecom Photons to Erbium-ion Ensembles
• Purcell-Enhanced Generation of Photonic Bell States via the Inelastic Scattering of Single Atoms
• Censorship of Quantum Resources in Quantum Networks
• Photo-luminescence properties of ion implanted Er3+-defects in 4H-SiCOI towards integrated quantum photonics
• Spin-photon Qubits for Scalable Quantum Network