Quantum entanglement is undoubtedly one of the most counter-intuitive phenomena arising from quantum physics, and forms the basis many of quantum information technologies. In order to further investigate this phenomenon, it is necessary to carry out experiments in laboratories. In our recent article [1], we present a new method for generating very general entangled quantum systems. This includes systems with many particles as well as many degrees of freedom.
The technique uses a combination of two fundamental properties of quantum physics: the superposition principle and the fact that information (or the lack thereof) can significantly change the properties of quantum states. In the new method, photon pairs are generated in a superposition from different locations. The paths of the photons are additionally aligned in such a way that specific information about where they originated from is deleted – or rather, never produced.
In this way, a large number of new quantum systems can be generated, which up to now could only be investigated theoretically. The idea can also be generalized to other quantum systems such as superconducting micro cavities or cold atoms.
The new way for generating entanglement uses only technology that is already available for 20 years. Interestingly, it has now been discovered by a computer algorithm [2]. The human part of our research team then analyzed the outputs of the computer program called MELVIN, and identified the trick, whereupon the generalizations presented were possible. It shows that computer programs that design new quantum experiments can provide inspiration for human scientists.
[1] Mario Krenn, Armin Hochrainer, Mayukh Lahiri, Anton Zeilinger, Entanglement by Path Identity, Phys. Rev. Lett. 118(8), 080401 (2017).
[2] Mario Krenn, Mehul Malik, Robert Fickler, Radek Lapkiewicz, Anton Zeilinger, Automated Search for new Quantum Experiments, Phys. Rev. Lett. 116(9), 090405 (2016).