Quantum Remote Entanglement and Telecommunication

Quantum networks are crucial for realizing secure communication based on the principles of quantum mechanics and developing more powerful quantum computing devices by connecting distributed computing resources. Scalable quantum networks can be realized in a trapped ion system through modular architecture leveraging ion-photon entanglement. Teleportation of quantum information between distant quantum nodes requires a resource called quantum entanglement. To develop large-scale quantum networks, quantum repeaters are essential for generating long-range entanglement through entanglement swapping.

Developing quantum repeater node

Our remote entanglement team focuses on developing a quantum repeater node based on a trapped ion system, which is an essential device for realizing scalable quantum networks. Trapped ion system offers an ideal entangled pair of a stationary memory qubit (ion) and a rapidly propagating communication qubit (photon). By measuring the photons emitted from two distant trapped ions in a Bell basis, we can generate an entangled pair of ion qubits deterministically.

We have successfully observed a Hong-Ou-Mandel interference of two photons emitted from trapped 174 Yb ions, and successively observed strong evidence of a remote entanglement between two separate ion qubits.

Quantum frequency conversion

The short wavelength of photons emitted by trapped ions yields a challenge for generating long-range entanglement over a few kilometers, due to the large attenuation of optical fiber. Therefore, to generate a long-range entanglement, we are developing a quantum frequency conversion (QFC) system for converting the ultraviolet (UV) photons emitted by a trapped ytterbium ion into telecommunication wavelength. Specifically, we are considering a 3-stage QFC setup for converting the UV wavelength of the photons into optical communication C–band.

By integrating the QFC system with our remote entanglement setup, we aim to make a long-distance entanglement between trapped ions. In recent developments, we successfully built our first QFC setup and demonstrated efficient conversion of ultraviolet photons from a trapped ytterbium ion into visible photons.