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24 May 2023
Light-matter entanglement demonstrated over 50-kilometer of metropolitan fiber link
Research paves the way to fully independent quantum nodes that could enable a quantum internet
Researchers have demonstrated entanglement between a multimode quantum memory and a photon, after propagation in metropolitan fiber links. This type of remote light-matter entanglement lays the groundwork for fully independent quantum nodes that could be used to build quantum networks for highly secure information transmission.
Samuele Grandi from the Institut de Ciencies Fotoniques (ICFO) at the Barcelona Institute of Science and Technology in Spain will present this research at the Optica Quantum 2.0 Conference and Exhibition, which will take place as a hybrid event 18-22 June in Denver, Colorado.
“Compatibility with the telecom network and with a solid-state quantum memory are some of the crucial properties required for the building blocks of the future quantum internet, which will connect remote quantum computers in a similar manner as the current ‘classical’ internet,” explained Grandi.
Delivering information over quantum networks requires sharing entanglement between the remote nodes of the network. One approach to accomplish this is by light to distribute entanglement across the current telecom network, connecting matter-based quantum systems located at the nodes. These quantum nodes serve as storage, manipulation, and application units for quantum information. Nonetheless, any system designed for long-distance quantum communication must overcome various obstacles to establish quantum correlations between a quantum memory and a telecom photon. One significant challenge involves implementing quantum-based multiplexed communication, enabling optical fibers to transmit multiple data channels simultaneously.
In the new work, the researchers performed a set of experiments over a quantum network testbed using a solid-state multi-mode quantum memory based on a praseodymium-doped crystal, which could be used for multiplexed quantum communication. They used spontaneous parametric down-conversion to create photon pairs that contained an idler photon at telecom wavelength for propagation in optical fibers and a signal photon which was stored in the quantum memory.
The researchers confirmed entanglement between the multimode quantum memory and a telecom photon after its transmission through up to about 50 kilometers of deployed optical fiber in a metropolitan area. Non-classical correlations and light-matter entanglement were maintained after the transmission, with degradation coming only from a reduced signal-to-noise ratio.
As an additional step toward a field-deployable system, the researchers moved the idler detection station to a separate location 17 km away and separated by about 47 km of fiber. With this setup, which required additional synchronization of the remote setups, they were also able to demonstrate non-classical correlations between two locations.
Grandi added, “The next step will involve increasing the storage time in the quantum memory, to ensure that it is still storing its photon when the telecom one has reached its destination. This will remove the need for post-selection, and open the way to experiments featuring entangled and remote quantum memories.”
About Optica Quantum 2.0 Conference and Exhibition
Optica Quantum 2.0 Conference and Exhibition brings together academics, engineers, national laboratories, and industry scientists working to advance quantum science and technology. Quantum 2.0 technical presentations cover a range of emerging technologies quantum computing and simulation, quantum communications systems, quantum metrology and sensors, quantum interconnects and more. Monitor the Quantum 2.0 for the latest information on conference registration. Media registration is free with credential. Digital assets are available as requested.
About Optica
Optica, Advancing Optics and Photonics Worldwide, is the society dedicated to promoting the generation, application, archiving and dissemination of knowledge in the field. Founded in 1916, it is the leading organization for scientists, engineers, business professionals, students and others interested in the science of light. Optica's renowned publications, meetings, online resources and in-person activities fuel discoveries, shape real-life applications and accelerate scientific, technical and educational achievement. Discover more at: Optica.org
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