An innovative platform for quantum computers and communications

Illustration depicting a quantum computer using a molecular crystal of europium. Credit: Christian Group

The ability to interact with light provides important functionality for quantum systems, such as communication over large distances, a key capability for future quantum computers. However, it is very difficult to find a material capable of fully exploiting the quantum properties of light. A research team from CNRS and the University of Strasbourg, supported by Chimie ParisTech-PSL and in collaboration with German teams from KIT, demonstrated the potential of a new material based on rare earths as a quantum photonic system. The results, published on March 9, 2022 in Natureshow the potential of molecular europium crystals for quantum memories and computers.

If quantum technologies promise a revolution in the future, they are still complex to implement. For example, quantum systems capable of interacting with light to create functionalities for processing information and communication via fiber optics in particular, remain rare. Such a platform should ideally comprise an interface with light as well as information storage units, ie a memory. Information processing must also be possible within these units, which take the form of spin. Developing materials that link spins to light at the quantum level has proven particularly challenging.

A team of scientists from the CNRS and the University of Strasbourg, with the support of Chimie ParisTech-PSL and in collaboration with German teams from KIT, succeeded in demonstrating the interest of molecular europium crystals for communications and quantum processors, thanks to their ultra-tight optical transitions allowing optimal interactions with light.

These crystals are the combined product of two systems already used in quantum technology: rare earth ions (like europium) and molecular systems. Rare earth crystals are known for their excellent optical and spin properties, but their integration into photonic devices is complex. Molecular systems generally lack spins (storage or calculation unit) or, on the contrary, have optical lines that are too broad to establish a reliable link between spins and light.

Molecular europium crystals represent a major breakthrough, as they have ultra-fine linewidths. This results in long-lived quantum states, which have been used to demonstrate the storage of a light pulse inside these molecular crystals. Additionally, a first building block for a light-controlled quantum computer has been obtained. This new material for quantum technologies offers unprecedented properties and opens the way to new computer and quantum memory architectures in which light will play a central role.

The results also open up broad research perspectives thanks to the many synthesizable molecular compounds.

A novel light spin interface with the europium(III) molecule advances the development of quantum computers

More information:
Philippe Goldner, Ultra-narrow optical linewidths in rare-earth molecular crystals, Nature (2022). DOI: 10.1038/s41586-021-04316-2.

Quote: Europium and light: an innovative platform for quantum computers and communications (March 9, 2022) retrieved on March 9, 2022 from

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