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Metasurfaces create super-sized neutral atom arrays for quantum computing
A new way of creating arrays of ultracold neutral atoms could make it possible to build quantum computers with more than 100 000 quantum bits (qubits) – two orders of magnitude higher than today’s best machines. The approach, which was demonstrated by physicists at Columbia University in the US, uses optical metasurfaces to generate the forces required to trap and manipulate the atoms. According to its developers, this method is much more scalable than traditional techniques for generating arrays of atomic qubits.
“Neutral atom arrays have become a leading quantum technology, notably for quantum computing, where single atoms serve as qubits,” explains atomic physicist Sebastian Will, who co-led the study with his Columbia colleague Nanfang Yu. “However, the technology available so far to make these arrays limits array sizes to about 10 000 traps, which corresponds to a maximum of 10 000 atomic qubits.”
Building on a well-established technique
In common with standard ways of constructing atomic qubit arrays, the new method relies on a well-established technique known as optical tweezing. The principle of optical tweezing is that highly focused laser beams generate forces at their focal points that are strong enough to trap individual objects – in this case, atoms.
To create many such trapping sites while maintaining tight control of the laser’s light field, scientists typically use devices called spatial light modulators (SLMs) and acousto-optic deflectors (AODs) to split a single moderately intense laser beam into many lower-intensity ones. Such arrays have previously been used to trap thousands of atoms at once. In 2025, for example, researchers at the California Institute of Technology in the US created arrays containing up to 6100 trapped atoms – a feat that Will describes as “an amazing achievement”.
A superposition of tens of thousands of flat lenses
In the new work, which is detailed in Nature, Will, Yu and colleagues replaced these SLMs and AODs with flat optical surfaces made up of two-dimensional arrays of nanometre-sized “pixels”. These so-called metasurfaces can be thought of as a superposition of tens of thousands of flat lenses. When a laser beam hits them, it produces tens of thousands of focal points in a unique pattern. And because the pixels in the Columbia team’s metasurfaces are smaller than the wavelength of light they are manipulating (300 nm compared to 520 nm), Yu explains that they can use these metasurfaces to generate tweezer arrays directly, without the need for additional bulky and expensive equipment.
The Columbia researchers demonstrated this by trapping atoms in several highly uniform two-dimensional (2D) patterns, including a square lattice with 1024 trapping sites; patterns shaped like quasicrystals and the Statue of Liberty with hundreds of sites; and a circle made up of atoms spaced less than 1.5 microns apart. They also created a 3.5 mm diameter metasurface that contains more than 100 million pixels and used it to generate a 600 x 600 array of trapping sites. “This is two orders of magnitude beyond the capabilities of current technologies,” Yu says.
Another advantage of using metasurfaces, Will adds, is that they are “extremely resilient” to high laser intensities. “This is what is needed to trap hundreds of thousands of neutral atom qubits,” he explains. “Metasurfaces’ laser power handling capabilities go several orders of magnitude beyond the state of the art with SLMs and AODs.”
Laying the groundwork
For arrays of up to 1000 focal points, the researchers showed that their metasurface-generated arrays can trap single atoms with a high level of control and precision and with high single-atom detection fidelity. This is essential, they say, because it demonstrates that the arrays’ quality is high enough to be useful for quantum computing.
While they are not there yet, Will says that the metasurface atomic tweezer arrays they developed “lay the critical groundwork for realizing neutral-atom quantum computers that operate with more than 100 000 qubits”. These high numbers, he adds, will be essential for realizing quantum computers that can achieve “quantum advantage” by outperforming classical computers. “The large number of qubits also allows for more ‘redundancy’ in the system to realize highly-efficient quantum error correction codes, which can make quantum computing – which is usually fragile – more resilient,” he says.
The Columbia team is now working on further improving the quality of their metasurfaces. “On the atomic arrays side, we will now try to actually fill such arrays with more than 100 000 atoms,” Will tells Physics World. “Doing this will require a much more powerful laser than we currently have, but it’s in a realistic range.”
The post Metasurfaces create super-sized neutral atom arrays for quantum computing appeared first on Physics World.
