Inside Short
- New research from Caltech and Oratomic suggests that fault-tolerant quantum computers may only need 10,000-20,000 qubits—much fewer than previously thought—which could speed up times up to this decade.
- The team has developed highly efficient quantum error correction systems using systems of neutral atoms, reducing the number of physical qubits from 1,000 to five.
- The findings suggest rapid progress towards efficient quantum machines capable of breaking current encryption methods, increasing the speed of migration to quantum-resistant cryptography.
- Figure: Traditional error correction schemes, shown at left, require hundreds of physical qubits per logical qubit. The new project, shown at right, reduces this situation by more than 100 times. (Caltech/Robert Hurt,IPAC-SELab)
WARNING – Quantum computers of the future may be closer to reality thanks to new research from Caltech and Oratomic, a Caltech-affiliated startup. Scientists and experimentalists teamed up to develop a new method to reduce the ridiculous errors in today’s quantum computers. Although it was thought that these machines needed millions of qubits to function properly (the equivalent of 1’s and 0’s in classical computers), new results show that a fully supervised quantum computer can be built with about 10,000 to 20,000 qubits. The need for fewer qubits means that quantum computers could be operational by the end of the decade.
The team proposes a new quantum error correction scheme that is much more efficient than previous methods. Quantum error correction is a process by which additional, redundant qubits are produced to correct errors, or errors, to enable the ultimate goal in the field: error-tolerant quantum computing.
The results use special quantum computing platforms built with neutral atoms, which act as qubits. Other platforms in development include superconducting circuits and trapped ions (ions are charged while neutral atoms are not). In a neutral atom system, laser beams known as optical tweezers are used to arrange atoms into qubit groups. Manuel Endres, a professor of physics at Caltech, and his colleagues recently created the largest qubit array ever assembled, consisting of 6,100 neutrally trapped atoms.
“Unlike other quantum computing platforms, neutral atomic qubits can be directly connected over large areas,” Endres says. “Optical tweezers can move one atom to the other end of the cluster and directly combine it with another atom.”
This powerful ability to move atoms is the key to the researchers’ error-correcting project, which they describe in a new report posted online. The first authors of the study are Madelyn Cain, Oratomic’s principal study scientist, and Qian Xu, a Sherman Fairchild Postdoctoral Fellow at Caltech who is now a research scientist at Oratomic. The main authors are Endres; John Preskill, Richard P. Feynman Professor of Theoretical Physics and Allen VC Davis and Lenabelle Davis Leadership Chair of the Institute for Quantum Information and Matter (IQIM) Caltech; Hsin-Yuan (Robert) Huang, associate professor of theoretical physics and William H. Hurt Scholar at Caltech who is currently on leave while serving as Oratomic’s CTO; and Dolev Bluvstein, visiting fellow in physics at Caltech and CEO of Oratomic. Other authors include Robbie King and Lewis Picard of Oratomic, and Harry Levine of Oratomic and UC Berkeley.
The results of the theory included designing new designs to reduce more than fixing errors.
“We spent years learning how to use this amazing ability of neutral atomic computers to program qubits dynamically,” says Cain. “Our results now make quantum computing with neutral atoms achievable by reducing the number of qubits by two orders of magnitude.”
Xu adds, “For decades, the number of qubits has been considered the main obstacle to the error tolerance of quantum computing. I hope our work helps to change that view.”
The report emphasizes that the team’s research means that fault-tolerant quantum computers may exist. In the past, quantum computing experts thought that such a precise machine would take another 10 or 20 years to develop.
“I’ve been working on fault-tolerant computing longer than some of my colleagues have been alive,” says Preskill. “Now we’re finally getting close.”
Huang says, “I always thought that theoretical research on the usefulness of large quantum algorithms was only interesting in the distant future.
Importantly, the fast timeline shows that the security of digital communications—which includes everyday financial transactions and many other types of private messages—may be vulnerable to data breaches sooner than expected. Today’s computers protect information using encryption methods, such as RSA (Rivest-Shamir-Adleman) and ECC (elliptic curve cryptography). In these ancient projects, data was encrypted using complex mathematical problems that are impossible for today’s computers to solve.
Quantum computers will have the ability to break down two-dimensional algorithms thanks to an algorithm developed by Peter Shor (BS ’81) in 1994, who is now a professor of applied mathematics at MIT. To protect against this situation, organizations around the world are moving to new coding systems that can withstand quantum computing attacks. The authors emphasize that the rapid progress towards efficient quantum computing highlights the importance of a secure and timely migration to these new cryptographic standards.
Quantum computers are based on the laws of quantum physics—the laws that govern the behavior of subatomic particles such as electrons and photons. In the quantum realm, particles exhibit properties that are foreign to our classical environment, including superposition, in which a particle exists in two places at the same time, and entanglement, in which particles remain closely related even after being separated by long distances.
Because nature is quantum at its core, quantum computers are set to have the power to unlock the mysteries of science, including gravity and room temperature, as well as other problems in chemistry, medicine, stability, machine learning and more.
The qubits at the heart of these machines are both flexible and tactile; however, these quantum states are unstable and prone to collapse. When this happens during reading, the information stored by the qubits is corrupted, leading to errors. To solve this problem, researchers have developed error correction methods, similar to those used by old computers, where redundant qubits are used to check for errors. But debugging is more difficult than quantum computers: Today’s standard systems often require about 1,000 physical qubits to work together as a single “logic” qubit—the qubit that performs the desired calculations.
A working quantum computer would need at least 1,000 logical qubits in total, but if each logical qubit was made up of 1,000 physical qubits, the entire computer would need 1 million qubits. Scaling up a quantum machine to a large size would be very difficult, so researchers are working on ways to reduce the number of qubits needed for each qubit. reasonable.
A new study explains how this can be achieved by using neutral atoms. In some error correction schemes, such as those using so-called surface codes, qubits arranged in two layers are limited to aligning with their immediate neighbors. With neutral atoms, qubits can be combined with many other qubits far away, enabling what scientists call high-level codes. In such protocols, each physical qubit can participate in many logical qubits instead of just one.
The new project means that each logical qubit can be embedded in as few as five or so qubits, as opposed to the 1,000 required by other methods.
“It’s surprising how well this works,” says Endres.
Although the results are theoretical, atomic neutralization techniques have advanced rapidly in recent years, and researchers have demonstrated primitive error-correcting processes with clusters of more than 6,000 atomic qubits. The biggest engineering challenges remain in integrating these capabilities into scalable systems, but new research suggests that atomically neutral architectures could eventually run quantum algorithms powerful enough to affect modern encryption. More broadly, when these systems reach thousands of logical qubits that make millions of operations, they are expected to provide many tools with a great scientific and economic impact.
“Fault-tolerant computers with neutral atoms is a rapidly emerging topic, and it was clear that there were many untrained opportunities to find shortcuts,” says Bluvstein.
The next steps are to take larger groups like that of Endres and his team and scale them up to a larger number while showing lower error rates, a method that will require further technological advances.
Scientists founded Oratomic, with Bluvstein as CEO, with the goal of building the world’s first fault-tolerant computers. Oratomic will work in collaboration with Caltech’s Advanced Quantum Computing Mission, a cross-campus effort, which will continue to study the fundamentals of quantum information processing. Over time, the Caltech team plans to have more “supercomputers” on campus to solve scientific problems.
“Now it’s time to make machines,” says Bluvstein.
The study “Shor’s algorithm is possible with 10,000 tunable atomic qubits” was done at Caltech and Oratomic. Caltech’s research was funded by Caltech. Manuel Endres and John Preskill also acknowledge support from the Center for Quantum Information and Matter, National Science Foundation (NSF) Physics Frontiers Center. Manuel Endres also acknowledges support from the NSF Quantum Leap Challenge Institute for Quantum Computation program. Qian Xu also acknowledges funding from the Walter Burke Institute for Theoretical Physics at Caltech.
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