Boosted communication rates? Entanglement multiplexing from Caltech

This is a preview issue of Quantum Campus, which shares the latest in quantum science and technology. Read by more than 1,400 researchers, we publish on Fridays and are always looking for news from across the country. Want to see your work featured? Submit your ideas to the editor.

Multiplexed quantum nodes

Caltech engineers demonstrated a quantum network of two nodes, each containing about 20 qubits.

“This is the first-ever demonstration of entanglement multiplexing in a quantum network of individual spin qubits,” Andrei Faraon, a professor at Caltech, said in an announcement. “This method significantly boosts quantum communication rates between nodes.”

The two nodes are made from yttrium orthovanadate crystals. Lasers excite ytterbium atoms within these crystals, causing each atom to emit a photon that remains entangled with it. Each atom has a slightly different optical frequency caused by imperfections within the crystal. The photons travel to a central location where they are detected. That detection triggers a quantum processing protocol that leads to the creation of entangled states between pairs of ytterbium atoms.

This work was published in Nature.

Ocelot

Amazon Web Services announced its entry into the quantum chip derby last week. Ocelot combines cat qubit technology, bosonic error correction, and noise-biased gates “onto a microchip that can be manufactured in a scalable fashion using processes borrowed from the microelectronics industry,” according to Amazon.

The chip is described in a technical report from Amazon and a paper in Nature. 

Hydrogen bonds for quartet states

Researchers at the University of Freiburg and the University of Strasbourg used perylenediimides and nitroxide radicals designed to self-assemble via hydrogen bonding to form quartet states that can be manipulated coherently using microwaves.

Relying on non-covalent bonds, the approach gives more precise control over the system’s properties and greater scalability compared to traditional approaches that rely on covalent bonds. It also allows “multiple qubits within a single molecule, creating a larger space for storing and processing information, compared with conventional qubits,” according to the team in a story in Chemistry World.

Read the details in Nature Chemistry.

Modular designs

IEEE Spectrum reviewed various modular computing approaches to linking multiple quantum chips. It covered designs by Xanadu, IBM, IonQ, Welinq, and Nu Quantum.

“To get to a million qubits, which is when you can start truly solving customer problems, you’re not going to be able to have them all on a single chip,” Xanadu CEO Christian Weedbrook said. “The only way to really scale up is through this modular networking approach.”

Quickbits

• Time magazine talks quantum with IBM CEO Arvind Krishna in an extended interview

• Parallel circuit implementation of variational quantum algorithms (npj Quantum Information)

• Efficient perovskite LEDs with tailored atomic layer number emission at fixed wavelengths (Science Advances)

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