Key takeaways
- Hypersensitivity to the environment has created problems leading to errors in quantum computing. The challenge is to get these machines to perform predictably and without making errors.
- A team of physicists, engineers and computer scientists will develop a design for a fault-tolerant quantum computer, not prone to these types of mistakes, based on trapped atomic ions.
- If successful, fault tolerance would allow quantum computers to perform long, reliable calculations that are impossible on current devices.
A UCLA-led team of physicists, engineers and computer scientists has been selected by the U.S. National Science Foundation for $4 million in funding through the NSF National Quantum Virtual Laboratory, or NQVL, a national initiative designed to accelerate the development of useful quantum technologies and make advanced quantum tools and testbeds available to researchers across the country.
The project, FTL: Accelerating Fault-Tolerant Quantum Logic, brings together researchers across UCLA's Division of Physical Sciences and the UCLA Samueli School of Engineering to develop the design for a fault-tolerant quantum computer based on trapped atomic ions. Led by UCLA physics professor Eric Hudson, the team aims to create a blueprint for a machine with 60 logical qubits — error-protected quantum bits — capable of performing digital quantum simulations beyond the reach of classical supercomputers.
Qubits are the basic units of quantum computing, analogous to bits in classical computing. But while classical bits can only operate in one of two positions at any given time ("on" or "off"), qubits take advantage of a quantum phenomenon known as "superposition" to operate in different positions simultaneously. But many factors can affect the position of a qubit, and a fundamental challenge of quantum computing is ensuring that qubits behave consistently and perform predictably, without errors. A logical qubit resolves this by encoding several qubits together in a cluster that makes errors easier to detect and contain without affecting the performance of other qubits.
"Quantum computers will only become useful when they can operate reliably despite the fragility of quantum information," said Hudson, professor of physics and astronomy at UCLA and principal investigator of the project. "This award allows us to bring together the hardware, error correction, software and user communities needed to design a system that can reach the fault-tolerant regime."
Building toward fault-tolerant quantum computing
Today's quantum computers are limited by errors that arise as quantum information interacts with its environment. Even very small disturbances, such as minor variations in temperature or minute inconsistencies in the materials of the device itself, can interfere with how quantum computers work. Fault-tolerant quantum computing seeks to overcome this challenge by encoding information into logical qubits protected by quantum error correction. If successful, fault tolerance would allow quantum computers to carry out long, reliable calculations that are impossible on current unstable or "noisy" devices.
The UCLA-led FTL team will focus on a trapped-ion architecture known as a quantum charge-coupled device. In this approach, individual charged atoms are moved through a chip-based device so that selected pairs of ions can interact. The architecture combines high-quality quantum operations with flexible connectivity, making it a promising path toward scalable, error-corrected quantum processors.
The project's central technical goal is to codesign the entire quantum computing stack — from atomic physics and chip architecture to quantum error correction, compilation, control systems and target applications. By designing the hardware and software together, the team aims to reduce the overhead normally required for fault-tolerant quantum computing.
The proposed processor is designed to support digital quantum simulation, one of the earliest anticipated applications of fault-tolerant quantum computers. Such simulations could help scientists study quantum many-body systems that are too complex for classical computers, with potential impact in materials science, chemistry, drug discovery and fundamental physics.
Teaming up to address key challenges
"Working together across the physical sciences and engineering enables us to address the key challenges in designing a quantum computer," said project co-leader Jens Palsberg, a professor of computer science at UCLA Samueli.
UCLA physicist and project co-leader Wesley Campbell, said, "I learn so much every time I speak with my colleagues on the computer-science side. They have a completely different way of understanding so many of the concepts. This allows us to cover ground more quickly by filling in each other's gaps."
Colleagues at UC Berkeley, Cornell University, the University of Maryland, the Georgia Tech Research Institute, UC Santa Barbara, SRI International, Quantinuum, Nvidia, Daylight Solutions, IonQ and other partners are also working on the project.
"This project is about more than building a better quantum device," Hudson said. "It is about creating an open, academic pathway to fault-tolerant quantum computing — one that trains the next generation of scientists and gives users access to machines capable of solving problems that matter."
