A new chip-scale device offers unprecedented control over laser frequencies, a key ingredient for large-scale quantum computing.

Researchers have achieved an important step forward in quantum computing by developing a device so small that it is almost 100 times thinner than a human hair.

The advance, reported in the journal Nature Communications, centers on a new type of optical phase modulator designed to precisely control lasers. This capability is critical for future quantum computers, which will rely on thousands or even millions of qubits—the basic units of quantum information—to perform complex calculations.

A key part of the achievement is how the devices are made. Instead of relying on specialized, hand-built components, the researchers used scalable manufacturing methods similar to those behind the processors found in computers, phones, vehicles, and home appliances—virtually everything powered by electricity (even toasters).

The work was led by Jake Freedman, an incoming PhD student in the Department of Electrical, Computer and Energy Engineering at the University of Colorado at Boulder, alongside Matt Eichenfield, a professor and the Karl Gustafson Endowed Chair in Quantum Engineering. They collaborated with researchers from Sandia National Laboratories, including co-senior author Nils Otterstrom, to create a device that combines an extremely small footprint with strong performance while remaining affordable to produce at large scale.

The chip operates by generating microwave-frequency vibrations that oscillate billions of times per second, which are used to control laser light with exceptional accuracy.

By harnessing these rapid vibrations, the device can precisely adjust the phase of a laser beam and generate new laser frequencies with high stability and efficiency. These capabilities are considered essential for advancing quantum computing, as well as emerging applications in quantum sensing and quantum networking.

Why quantum computers depend on precise optical frequency control

Among the leading approaches to quantum computing are trapped-ion and trapped-neutral-atom systems, which store information in individual atoms.
To operate these qubits, researchers “talk” to each atom using precise laser beams, allowing them to give the instructions to do computations.
Each laser’s frequency must be tuned with extreme accuracy, often to within billionths of a percent or even smaller.

“Creating new copies of a laser with very exact differences in frequency is one of the most important tools for working with atom- and ion-based quantum computers,” Freedman said. “But to do that at scale, you need technology that can efficiently generate those new frequencies.”

Today, those frequency shifts are made using bulky table-top devices that consume significant amounts of microwave power.

Current setups work well for small lab experiments and quantum computers with small numbers of qubits, but they cannot scale to the tens or hundreds of thousands of optical channels required for future quantum computers.

“You’re not going to build a quantum computer with 100,000 bulk electro-optic modulators sitting in a warehouse full of optical tables,” Eichenfield said. “You need some much more scalable ways to manufacture them that don’t have to be hand-assembled and with long optical paths. While you’re at it, if you can make them all fit on a few small microchips and produce 100 times less heat, you’re much more likely to make it work.”

The device can generate new frequencies of light through efficient phase modulation that consumes roughly 80 times less microwave power than many commercial modulators.

Using less power reduces heat and allows many more channels to be placed close together—even on a single chip.

Together, these features turn the chip into a powerful, scalable system for managing the complex dance that atoms must perform to make quantum computations.

Built using the world’s most scalable manufacturing technology

One of the most significant aspects of the project is that it was produced entirely in a “fab” or foundry, the same type of facility used to make advanced microelectronics.

“CMOS fabrication is the most scalable technology humans have ever invented,” Eichenfield said.

“Every microelectronic chip in every cell phone or computer has billions of essentially identical transistors on it. So, by using CMOS fabrication, in the future, we can produce thousands or even millions of identical versions of our photonic devices, which is exactly what quantum computing will need.”

According to Otterstorm, they’ve taken modulator devices, which were previously expensive and power hungry, and made them more efficient and less bulky.

“We’re helping to push optics into its own ‘transistor revolution,’ moving away from the optical equivalent of vacuum tubes and towards scalable integrated photonic technologies,” Otterstorm said.

The team is now developing fully integrated photonic circuits that combine frequency generation, filtering, and pulse-carving on the same chip, bringing the goal of a complete operational chip closer to reality.

Moving forward, they will collaborate with quantum computing companies to test versions of these chips inside state-of-the-art trapped-atom and trapped-neutral-atom quantum computers.

“This device is one of the final pieces of the puzzle,” Freedman said. “We’re getting close to a truly scalable photonic platform capable of controlling very large numbers of qubits.”