The Rise of Neutral-Atom Quantum Computing: A New Challenger in the Race to Full-Scale Quantum Computing

Thursday - April 4 2024, 09:24 UTC - 7 months ago

Neutral-atom quantum computing is gaining traction as a potential solution to the challenge of scaling up quantum computers. Recent advances have overcome previous limitations, making it a promising contender for commercialization. Neutral-atom qubits use the phenomena of superposition and entanglement for computation. Harvard researchers have successfully performed quantum computations using programmable quantum circuits with hundreds of neutral-atom qubits.

At the end of last year, the tech giant IBM announced what might sound like a milestone in quantum computing: the first-ever chip, called the Condor, with more than 1,000 quantum bits, or qubits. Given that this was barely two years after the company unveiled the Eagle, the first chip with more than 100 qubits, it looked as though the field was racing forward. Making quantum computers that can solve useful problems beyond the scope of even the mightiest of today’s classical supercomputers demands scaling them up even more — to perhaps many tens or hundreds of thousands of qubits. But that’s surely just a matter of engineering, right? .

Not necessarily. The challenges of scaling up are so great that some researchers think it will require totally different hardware from the microelectronics used by the likes of IBM and Google. The qubits in the Condor and in Google’s Sycamore chip are made from loops of superconducting material. These superconducting qubits have so far been the hare in the race to full-scale quantum computing. But now there’s a tortoise coming from behind: qubits made from individual atoms.

Recent advances have transformed these "neutral-atom qubits" from outsiders to leading contenders.

"The last two or three years have seen more rapid advances than any previous such period," said the physicist Mark Saffman of the University of Wisconsin, Madison, who counted at least five companies racing to commercialize neutral-atom quantum computing.

Like the bits in ordinary computers, qubits encode binary information — 1s and 0s. But whereas a bit is always in one state or the other, the information in a qubit can be left indeterminate, in a so-called "superposition" that gives weight to both possibilities. To carry out a computation, qubits are linked using the phenomenon called quantum entanglement, which makes their possible states interdependent. A particular quantum algorithm might demand a succession of entanglements between different sets of qubits, and the answer is read out at the end of the computation when a measurement is made, collapsing each superposition down to a definite 1 or 0.

The idea of using the quantum states of neutral atoms for encoding information this way was proposed in the early 2000s by the Harvard physicist Mikhail Lukin and colleagues, and also by a group led by Ivan Deutsch of the University of New Mexico. For a long time, the broader research community agreed that neutral-atom quantum computing was a great idea in principle, Lukin said, but that "it just doesn’t work out" in practice.

"But 20 years later, the other approaches haven’t closed the deal," Saffman said. "And the skill set and the techniques needed to make neutral atoms work have been gradually evolving to the point where they are looking very promising." .

Lukin’s lab at Harvard, working with the Harvard group of Markus Greiner and that of Vladan Vuletic at the Massachusetts Institute of Technology, has been among those leading the way. In December, these researchers reported that they created programmable quantum circuits with hundreds of neutral-atom qubits and had performed quantum computations and erro .