New funding to engineer rare-earth qubits could fast-track quantum technology

In today’s digital age, information is represented by binary bits, or zeros and ones. But quantum information technology introduces a new kind of representation called a qubit, or quantum bit, which is zero and one at the same time. Thanks to qubits, quantum computers have the potential to be millions of times more powerful than today’s supercomputers.

Tian Zhong, an assistant professor at the Pritzker School of Molecular Engineering (PME) at the University of Chicago, was awarded a grant in which he aims to create a new form of qubits using rare-earth elements doped in solids. Rare-earth elements refer to the lanthanide series, a family of atoms in the periodic table with atomic numbers from 58 to 71.

Zhong chose to use rare-earth atoms because they have demonstrated superb quantum coherence properties desirable for quantum technology. In addition, these materials are already ubiquitous in electronic gadgets such as TV displays, laser pointers, and mobile phones.

His proposal, titled “Engineering rare-earth hyperfine qubits for quantum information technology” was accepted for three years of funding through the Young Investigator Program (YIP) of the Army Research Office (ARO), an element of the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory. The objective of the YIP is to support exceptional young university faculty members pursuing fundamental research.

“The YIP award will allow us to explore new ways to make qubits by effectively painting rare-earth atoms one at a time onto industry-standard wafers,” said Zhong. “This would allow us to mass-produce high-quality qubits and quantum devices on a large scale.”

“This award recognizes the tremendous potential of Tian’s work in the practical implementation of quantum engineering,” said Matthew Tirrell, dean of Pritzker Molecular Engineering. “With this support, his research could help accelerate the adoption of quantum technologies.”

The new silicon

To engineer qubits, Zhong said one must use the atom's discrete, internal energy levels to encode quantum state zero and one. Creating a new form of atomic qubits on wafers, however, is uncharted territory.

As Zhong’s team works with rare-earth atoms, one challenge will be efficiently controlling the quantum state of the qubits while desensitizing them to noise in the solid-state host. Zhong’s team proposes to overcome this challenge by encoding quantum information in the hybridized energy level between nuclear and electronic spins. The hybridized nuclear-electron state combines the advantages of nuclear spins and electron spins to make a high-performance qubit.

Today, all digital devices are powered by chips made out of silicon, and Zhong hopes that rare-earth elements, already common in electronics, will become the silicon of quantum devices.

“We would like to reinvent this ‘common’ material into something new and that can decisively empower future quantum technologies,” he said, “just as silicon material transformed digital electronics 50 years ago.”

Bringing quantum devices to life

Quantum technology, once it can be produced on a large scale, has the potential to revolutionize computing, sensing, secure communications, and medicine.

But much of the quantum technology that could significantly impact society simply doesn’t exist yet. That’s why finding suitable materials to develop quantum devices is crucial.

"Solid-state systems based on rare-earth elements are potentially an excellent platform for qubit systems of interest to the Army, but there is a lot we don't know yet about them," said Sara Gamble, quantum information science program manager at the ARO. "This exciting work will help us better understand the potential for these qubits to be useful for applications ranging from quantum computing to quantum networking."

Using rare-earth elements in this way has not been done before, but it could be the key to enabling the mass production of quantum devices such as quantum memories, quantum repeaters, and quantum transducers.

“If successful, we might have found the quantum equivalent of silicon, with rare-earth qubits reassembling silicon transistors, which could fuel rapid advancements in quantum technologies in communications, computing, and sensing,” said Zhong.