University of Iowa researchers have modeled how to minimize interference to yield a consistent single photon stream (shown here in this image), an advance that could make quantum computing and communications more reliable and more secure. Credit: Ravitej Uppu lab, University of Iowa

University of Iowa researchers have discovered a method to "purify" photons, an advance that could make optical quantum technologies more efficient and more secure.

The work is published in the journal Optica Quantum.

The researchers investigated two nagging challenges to creating a steady stream of single photons, the gold standard method for realizing photonic quantum computers and secure communication networks. One obstacle is called laser scatter, which occurs when a laser beam is directed at an atom, causing it to emit a photon, which is a single unit of light. While effective, the technique can yield extra, redundant photons, which hampers the optical circuit’s efficiency, much like a wayward current in an electrical circuit.

The other challenge involves how atoms can sometimes interact with a laser beam. In rare instances, an atom will emit more than a single photon. In those cases, the optical circuit’s fidelity is compromised because the extra photons disrupt the desired single-file photon line.

In the study, Matthew Nelson, a graduate student in the Department of Physics and Astronomy, figured out that the color on the wavelength spectrum and the waveform generated when an atom emits more than one photon are nearly identical to the wavelength spectrum and the waveform produced by the laser beam itself. What that means, the researchers report, is that the two essentially can be tuned to cancel each other out.

"We have shown that stray laser scatter, typically considered a nuisance, can be harnessed to cancel out unwanted, multi-photon emission," says Ravitej Uppu, assistant professor in the Department of Physics and Astronomy and the study’s corresponding author. "This theoretical breakthrough could turn a long-standing problem into a powerful new tool for advancing quantum technologies."

In photonic computing, light is used to carry out operations faster or more efficiently than with electronics. Today’s computers use bits—streams of electrical or optical pulses representing ones or zeroes. Quantum computers, on the other hand, use qubits, which are typically subatomic particles, such as photons. A growing number of startup companies believe photonic systems will be central to advances in quantum computing.

The single-photon line is important to that advance, in large part because it is orderly, controllable, and easier to scale up. Think about it like herding elementary school students single file through the cafeteria lunch line, rather than as a jumbled group. That tidy photonic line also lessens chances of information being hacked or eavesdropped upon, much like a conversation shared between two students in a single-file line is less likely to be heard by the entire group.

"If we can control exactly how the laser beam shines on an atom—the angle at which it’s coming, the shape of the beam, and so on—you can actually make it cancel out all the additional photons that the atom likes to emit," Uppu explains. "We would be left with a stream that is actually very pure."

The research theoretically eliminates two barriers to accelerating photonic, or light-based, circuitry. Removing these obstacles could help usher in more advanced quantum computers and more secure communication networks. The next step is to test these ideas, which the researchers plan to do soon.

More information: Matthew D. Nelson et al, Noise-assisted purification of a single-photon source, Optica Quantum (2025). DOI: 10.1364/opticaq.565878

Citation: Theoretical results could lead to faster, more secure quantum technology (2025, December 10) retrieved 10 December 2025 from https://phys.org/news/2025-12-theoretical-results-faster-quantum-technology.html

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