From The Lab: Europium's immense promise for quantum computing

Recently developed quantum technologies are the forefront of computing and could revolutionise the fields of computing and communications. Thanks to their unique capabilities, quantum computers can either solve algorithms that classical computers cannot solve or significantly reduce computation time.

CNRS researcher Diana Serrano and her team probed the optical quantum properties of a Europium molecule. © Dhananjay Khadilkar

However, implementing the principles of quantum mechanics to build a workable quantum computer remains a big challenge.

A big part of that challenge is to find the right material that can enable the full potential of the quantum properties. 

Now, research teams from France and Germany have demonstrated the potential of a rare earth material called europium in a molecular form. 

“Atoms of rare earth materials such as europium are unique as they can exhibit superposition states with energies corresponding to the optica, microwave, and/or radiofrequency domains” says Diana Serrano, CNRS researcher at Chimie ParisTech.

Superposition refers to the existence of two different states of a quantum particle (electron or photon) at the same time. These two states represent quantum bits, which are used for coding information.

Classical vs. quantum computing

In classical computing, information is coded in bits that can have one of only two values, 0 or 1, whereas quantum bits (or qubits) can take the values of 0 and 1 simultaneously which tremendously boosts the computing power

“For instance, a photonic superposition state (e.g. in the form of light), can be transferred to the atom as a superposition between the electronic excited and ground states” she says.

According to Serrano, while the light superposition state can be used for communications, the superposition state is used for memory and processing.

“In the case of rare earth materials such as europium, both these operations can take place in the same atom. The information arrives in the form of light which is stored in the optical state and transferred to the spin state for memory and processing,” she said.

For this particular experiment, Serrano and her colleagues focused on probing the optical quantum properties of the europium molecule.

However, before it could be tested at Chimie ParisTech, the molecular crystal had to be synthesised in a laboratory. This was done at Karlsruhe Institute of Technology (KIT) in Germany.

Once the material was ready, it was brought to the ENSCP-Chimie ParisTech lab in Paris where it was prepared and ultimately used in tests. 

Serrano and her team used spectroscopic techniques using lasers and cooling systems to demonstrate the quantum properties of the europium molecule such as storage and communication.

Serrano said that efficient optical superposition states are vital for quantum communication through optical fibres.