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Developing a new approach for building quantum computers

UCLA-led team develops new approach to building quantum computers

An artist’s performance shows the researchers’ quantum functional groups (brightly colored spheres) bonding with larger molecules. Credit: Stephan Sullivan

Quantum computing, while still in its infancy, has the potential to dramatically increase processing power by exploiting the strange behavior of particles at the smallest scale. Some research groups have already reported performing calculations that would take a traditional supercomputer thousands of years. In the long run, quantum computers could provide unbreakable coding and simulations of nature beyond today’s capabilities.

A UCLA-led interdisciplinary research team with employees from Harvard University has now developed a fundamentally new strategy for building these computers. While the current state of the art uses circuits, semiconductors and other electrical instruments, the team has devised a game plan based on the ability of chemists to design custom atomic building blocks that determine the properties of larger molecular structures. when they are posted. together.

The findings, published last week in Natural Chemistrycould eventually lead to a jump in quantum processing power.

“The idea is, instead of building a quantum computer, let chemistry build it for us,” said Eric Hudson, UCLA’s David S. Saxon Presidential Professor of Physics and corresponding author of the study. “We’re all still learning the rules for this kind of quantum technology, so this work is very sci-fi right now.”

The basic units of information in traditional computing are bits, each of which is limited to one of only two values. In contrast, a group of quantum bits — or qubits — can have a much wider range of values, exponentially increasing a computer’s processing power. It takes more than 1,000 normal bits to represent only 10 qubits, while 20 qubits require more than 1 million bits.

That property, at the heart of quantum computing’s transformational potential, depends on the counterintuitive rules that apply when atoms interact. For example, when two particles interact, they can become connected or entangled, so measuring the properties of one determines the properties of the other. The entanglement of qubits is a requirement of quantum computing.

However, this entanglement is fragile. When qubits encounter subtle variations in their environment, they lose their “quantumness,” which is necessary to implement quantum algorithms. This limits the most powerful quantum computers to less than 100 qubits, and to keep these qubits in a quantum state requires large machines.

To practically apply quantum computing, engineers need to scale up that computing power. Hudson and his colleagues think they took a first step with the study, where the theory led the team to tailor molecules that protect quantum behavior.

The scientists developed small molecules that contain calcium and oxygen atoms and act as qubits. These calcium-oxygen structures form what chemists call a functional group, meaning it can join in almost any other molecule while also imparting its own properties to that molecule.

The team showed that their functional groups retained their desired structure even when attached to much larger molecules. Their qubits can also withstand laser cooling, a key requirement for quantum computing.

“If we can bind a quantum functional group to a surface or a long molecule, we might be able to control more qubits,” Hudson said. “It should also be cheaper to scale up because an atom is one of the cheapest things in the universe. You can make as many as you want.”

In addition to the potential for next-generation computers, the quantum functional group could be a boon for fundamental discoveries in chemistry and the life sciences, for example by helping scientists discover more about the structure and function of various molecules and chemicals in the human body. .

“Qubits can also be extraordinarily sensitive measurement tools,” said study co-author Justin Caram, a UCLA assistant professor of chemistry and biochemistry. “If we could protect them so that they can survive in complex environments such as biological systems, we would be armed with so much new information about our world.”

Hudson said the development of a chemical-based quantum computer could realistically take decades and is not certain to succeed. Future steps include anchoring qubits to larger molecules, coaxing tethered qubits to interact as processors without unwanted signals, and entangling them to work as a system.

The project was set up by a Department of Energy grant that gave the physicists and chemists the opportunity to break through subject-specific jargon and speak in a common scientific language. Caram also credits UCLA’s atmosphere of easy collaboration.

“This is one of the most intellectually satisfying projects I’ve ever worked on,” he said. “Eric and I first got to know each other over lunch at the Faculty Center. This grew out of nice conversations and being open to talking to new people.”

Quantum computer works with more than zero and one

More information:
Guo-Zhu Zhu et al, Functionalizing Aromatic Compounds with Optical Cycling Centers, Natural Chemistry (2022). DOI: 10.1038/s41557-022-00998-x

Provided by the University of California, Los Angeles

Quote: Developing a New Approach to Building Quantum Computers (2022, Aug. 2), retrieved Aug. 3, 2022 from https://phys.org/news/2022-08-approach-quantum.html

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