Researchers at the University of Iowa have identified a new way to "purify" photons, a development that could improve both the performance and security of light based quantum technologies. By refining how single particles of light are produced, the approach aims to overcome long standing limitations in optical quantum systems.

The team focused on two major obstacles that make it difficult to generate a reliable stream of single photons, which are essential for photonic quantum computers and secure communication networks.

One challenge is known as laser scatter. When a laser shines on an atom to trigger the release of a photon, the process can also produce extra, unwanted photons. These additional particles act like interference in an optical circuit, reducing efficiency in much the same way stray electrical current disrupts a conventional circuit.

A second issue arises from the way atoms sometimes respond to laser light. In rare cases, an atom emits more than one photon at a time. When that happens, the precise order needed for quantum operations breaks down, since the extra photons interfere with the intended one by one flow.

Using Laser Noise to Cancel Unwanted Light

In the new study, Matthew Nelson, a graduate student in the Department of Physics and Astronomy, found an unexpected connection between these two problems. He discovered that when an atom releases multiple photons, the resulting wavelength spectrum and wave form closely match those of the laser light itself.

According to the researchers, this similarity means the two signals can be carefully adjusted to cancel each other out. In effect, the laser scatter that usually causes trouble can be used to suppress the unwanted photon emissions.

"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."

Why Single Photons Matter for Quantum Computing

Photonic computing relies on light rather than electricity to perform calculations, offering the potential for faster and more efficient systems. Conventional computers operate using bits -- streams of electrical or optical pulses that represent ones or zeroes. Quantum computers instead use qubits, which are often subatomic particles such as photons.

Many emerging technology companies believe photonic platforms will play a key role in the future of quantum computing. A stable, well controlled stream of single photons is central to making that vision practical.

An orderly photon stream is easier to manage and scale, and it also improves security. The researchers compare it to guiding students through a cafeteria line one at a time rather than letting them move as a crowd. In the same way, a neat single photon line reduces the risk of data being intercepted or overheard.