Technique Detects Entangled Quantum States

From Technology Review: The laws of physics make things that are very small – like atomic particles – act differently than objects in the larger world where we reside. One weird quantum property is entanglement, which allows properties of particles like atoms, photons and electrons to remain linked, or synchronized, regardless of the physical distance between the particles. Entanglement is also very sensitive to disturbances and therefore difficult to measure.

Entanglement figures prominently in efforts to build quantum computers, which use properties of particles to compute. Quantum computers promise to be fantastically fast at certain types of large problems, including those that would render today’s cryptography useless.

Entanglement also figures in quantum cryptography schemes that offer theoretically perfect security.

Researchers from the University of Rome in Italy have pushed the schemes forward by demonstrating a method for detecting entanglement. The method could be used practically in five to ten years, according to the researchers. The work appeared on Physical Review Letters (Detection of Entanglement with Polarized Photons: Experimental Realization of an Entanglement Witness).

[Note: besides its relevance in quantum computing technology, entanglement is important for our understanding of the structure of reality as a fundamental level and can be used to distinguish experimentally between different formulations of quantum physics.]