A research team from the Department of Physics and Astronomy at the University of Iowa recently proposed a new theoretical solution that is expected to "purify" the photon flow output by quantum light sources from the source, paving the way for more efficient and safer photon quantum computing and quantum communications.
In existing photon quantum technology, single-photon sources are the core of quantum circuits, but obtaining stable and pure single-photon flows has always faced two major technical bottlenecks. The first is laser scattering: In experiments, atoms are usually irradiated with lasers to stimulate them to emit photons, but at the same time, additional scattered photons are introduced, which is equivalent to "stray current" in the optical circuit, reducing system efficiency. The second problem comes from the sporadic multi-photon emission events of the atoms themselves. When the atoms release multiple photons at once, the photon flow that should be "passing in a single file" is disrupted, weakening the accuracy and controllability of the optical quantum circuit.
The key finding of the study is that when atoms occasionally emit multiphotons, the spectral color distribution and waveform of these multiphotons are highly similar to the laser light itself that excites them. It is this similarity that led researchers to realize that they can actively utilize laser scattering, a component originally regarded as "noise". Through fine control, laser scattered light and multi-photon emission can interfere with each other in space and phase, thereby canceling out unnecessary excess photons. The theoretical model given by the research team shows that under suitable conditions, this "noise assist" can significantly suppress multi-photon components and retain purer single-photon output.
In photon quantum computing, information is carried by qubits such as photons. Compared with traditional electronic bits, photons have advantages in speed, transmission loss, and anti-interference. Therefore, they are regarded by many start-ups as one of the important technical routes for future quantum computing and quantum communications. The controllability and purity of single-photon sources are directly related to the scalability and security of the system: ordered single-photon streams not only facilitate large-scale line integration, but also reduce the risk of information being eavesdropped or tampered with during transmission.
Ravitej Uppu, corresponding author of the paper and assistant professor in the Department of Physics and Astronomy at the University of Iowa, pointed out that by controlling parameters such as the incident angle and beam shape of the laser irradiation atoms, excess photons can be accurately offset in theory, making the remaining photon flow "very pure." The research theoretically overcomes the two major obstacles of laser scattering and multi-photon emission, and is regarded as an important step in accelerating photon quantum circuits and promoting a new generation of quantum computers and secure communication networks. In the next stage, the team plans to verify this theory in the laboratory and provide a feasible engineering implementation path for future photonic quantum devices.
According to reports, the research, titled "Noise-Assisted Single-Photon Source Purification," was published in the journal Optica Quantum and was funded by the Office of the Under Secretary of Defense for Research and Engineering and the University of Iowa's Office of the Vice President for Research. The researchers said that if the experimental verification goes smoothly, this idea is expected to be applied to a variety of photon quantum platforms, providing new technical tools for building high-fidelity quantum networks.
Compiled from /ScitechDaily