Revolution in quantum photonics: New filter protects entanglement!

Revolution in quantum photonics: New filter protects entanglement!

An international research team consisting of scientists from the universities of Rostock, Southern California, Central Florida, Pennsylvania State and Saint Louis has made groundbreaking progress in quantum photonics. The discovery was published March 28, 2025 in the journal Science and offers a new approach to protecting optical entanglement. This work has the potential to significantly advance the development of advanced quantum technologies, which is of great importance given the International Years of Quantum Science and Technology proclaimed by the United Nations [uni-rostock.de] reports that...

Quantum mechanics is revolutionizing our understanding of nature at the smallest scales and is the basis for modern technologies, including quantum computers, which can calculate faster than classical computers. Entanglement is central because it is not only essential for calculations, but also enables the secure transmission of cryptographic keys and increases the sensitivity of sensors. However, this entanglement is fleeting and can easily be lost due to decoherence, such as thermal noise.

New entanglement filter

The research team, led by Prof. Alexander Szameit, has overcome the challenges of preserving entanglement in photonic circuits. Their method uses so-called “wires for light,” which allow photons to “jump” between adjacent channels. This technique uses targeted tuning of the coupling according to anti-parity time symmetry to remove unentangled components from the system. The newly developed entanglement filter achieves near-ideal precision for both single- and two-photon excitations and is robust to decoherence.

In addition, it was emphasized that these findings are of great importance not only for academic research, but also for practical applications in quantum communication. Quantum communication enables tap-proof exchange of keys for encoding security-relevant information, based on physical principles such as quantum entanglement and the superposition principle. In contrast to algorithmic cryptography methods, this system could be used in high-security networks [fraunhofer.de] reports that...

Technological advances in quantum communication

The Fraunhofer Institutes are working on the development of quantum communication systems and optical link technologies in the QuNET initiative. The goal is to create the basis for secure connections between different wavelength bands and transmission media. Elementary building blocks of these systems include precision optical reflecting telescopes, polarization-entangled photon pair sources and high-resolution detection systems. These components not only enable the transmission of polarization-encoded quantum states, but also guarantee high key exchange rates.

Security is based on the proven BBM92 protocol for polarization-entangled photons, which promises absolute security in communication. Quantum cryptography, as anchored in the BB84 protocol, allows information to be transmitted with a high level of security that is resistant to future quantum computers [das-wissen.de] reports that...

Additionally, the need for quantum repeaters to extend transmission distances is highlighted, as quantum information degrades over long distances. These technical challenges and limitations highlight the dynamic nature of the research area and the need for further investment in fundamental research and the development of standardized quantum encryption protocols.

Overall, recent research shows great potential for quantum communication, not only in terms of unbreakable security and global reach, but also faster information transmission in the digital age.