| Date | 25th, Apr 2022 |
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A university-industry collaboration has successfully run a quantum algorithm on a type of quantum computer known as a cold atom quantum computer for the first time. The achievement by the team of scientists from the University of Wisconsin–Madison, ColdQuanta, and Riverlane brings quantum computing one step closer to being used in real-world applications.
Practical quantum computers could solve complex problems, known as algorithms, that classical computer cannot. This could benefit many applications, such as logistics, drug discovery, and computational modeling of quantum processes.
The central components of the quantum computer in the Saffman lab. Practical quantum computers could solve complex problems that regular computers cannot. Image credit: Saffman Lab
Running a quantum algorithm on the cold atom-style computer is a proof of concept that this approach could work.
“There’s a race to build a useful quantum computer, and there’s a handful of different approaches that are being developed to that end,” says Mark Saffman, a physics professor at UW–Madison, director of the Wisconsin Quantum Institute, and chief scientist for quantum information at ColdQuanta. “Cold atom qubits is one of the five approaches actively being developed. This paper presents the capability of running quantum circuits and quantum algorithms using cold-atom qubits.”
Headed by Saffman, the team demonstrated two key achievements in a study published in Nature.
We have entangled up to six neutral atoms with long lifetimes. Previous neutral atom quantum computers have used bits in a shorter-lived state. “One of the benefits [of our approach] is that it’s a longer-lived state,” says Trent Graham, a scientist at UW–Madison and the lead author of the study. “We showed that we have coherence remaining in these states on up to milliseconds. In the [previously-demonstrated state], it decayed three to four hundred times faster.”
Successfully ran two quantum algorithms on their quantum computer. The first, a quantum phase estimation algorithm, is a common problem in chemistry that measures the molecular energy of an atom. The second is a strategy problem known as MaxCut, which has applications in logistics deployment and pattern recognition.
One advantage of neutral atom qubits used in this approach is that they do not naturally interact with each other, so it is easier to control when they are “on” or “off.”
The collaboration was key to the team’s success. The UW–Madison group conceived of and performed much of the work. ColdQuanta engineers, in partnership with the UW team, designed and fabricated key subsystems of the quantum computer and Riverlane staff contributed to circuit design, optimization, and simulation.
One of the first steps in preparing the qubits is to load them into an optical lattice array. Each spot on the grid can hold up to one atom at a time, and this image shows the occupancy of each spot in the grid as a composite of hundreds of experiments. Image credit: Saffman Lab
The quantum algorithms were fundamental. But the work suggests that quantum computers that outcompete traditional ones are on the horizon.
“These were elementary computations, but as you go to higher and higher circuit depth and more qubits, then it is actually possible to get to the regime where classical computers can’t easily calculate these problems,” Graham says.
As is familiar with other classes of quantum computers, there is no error correction mechanism in place with this team’s computer.
Source: University of Wisconsin-Madison
