Is quantum mechanics the key to the development of a new-generation, ultra-fast communication system? A project funded by a team of European researchers has made considerable progress in trying to answer this question.
“Today’s society is based on rapid access to information,” said SIPHON project coordinator Klaus Jöns of Sweden’s KTH Royal Institute of Technology. “Staying ahead of information is crucial in business, finance, politics and security. Most of our information exchanges are now of course done over the Internet, but this means of communication has limitations. In addition, the transfer of data is not secure.”
The EU-funded project explored the fascinating and mysterious world of quantum mechanics to determine the feasibility of a future networks capable of handling massive volumes of data flow. “The idea is that at the quantum level, we can encode information on the smallest quanta of energy, a single particle of light called photon,” he explains. “This would not only reduce the amount of energy needed for the transfer of information, but also fully secure communication through the principles of quantum mechanics.”
The project focused specifically on a quantum phenomenon known as non-locality. This quantum mechanical effect is already well known, and several experiments have been performed, usually involving two entangled photons. A projective measurement on one photon instantly collapses the state of the other entangled photon at a remote location. However, the non-locality of a single particle, especially a single photon, raises a fundamental question: can a single photon be simultaneously in different places?
“Non-locality, described by Albert Einstein as ‘remote sinister actions’ occurs when spatially separated particles are instantly influenced by an action that takes place in a part of the system and in one place, says Jöns. “As part of this project, our goal is to determine whether modern nanoscale quantum light sources can demonstrate non-locality in photons.”
Jöns and his team have used nanoscale devices, also known as artificial atoms, in their experiments and have shown that they are indeed excellent sources of unique photons. These artificial atoms are also more efficient than the natural atoms in many cases. “These nanoscale semiconductor quantum light sources have the lowest multi-photon emissions we can do without,” says Jöns. “They can also be used to generate deterministic entanglement photon pairs.”
This new method of generating entangled photon pairs on demand could help speed up the research. The project team also discovered that these quantum transmitters are “flashing”, which means they sometimes do not emit light. This discovery, says Jöns, should be taken into account when developing future applications in quantum communications.
While it is clear that single and entangled photons are essential components of quantum network construction, Jöns points out that much more fundamental research is needed to identify the best quantum light sources that meet the most stringent needs.
“This Marie Curie project has allowed me to build my own network of collaborators,” he says. “It was a milestone that helped me become more independent and build my own research portfolio. This step also gave me a unique research environment with excellent supervision and excellent coaching, which in my case was provided by Professor Val Zwiller of KTH Stockholm. “