Physicists have experimentally demonstrated an optical system based on an unconventional class of quantum mechanical systems that could lead to the development of new quantum optical devices. The system is called a "PT-symmetric quantum walk," since it consists of single photons that occupy a superposition of states, called quantum walks, that obey parity-time (PT) symmetry—the property in which a system's coordinates in space and time can have their signs reversed without inherently changing the system.
The physicists, led by Peng Xue at Southeast University in Nanjing, have published a paper on the PT-symmetric quantum walks in a recent issue of Nature Physics.
"We present an experimental work tying together three concepts—-non-unitary quantum walks at a single-photon level, PT symmetry, and topological edge states originating from Floquet topological phases," Xue told Phys.org. "Each of these three concepts has attracted much attention in the past years in the scientific community. The interplay of these elements in our experimental system will no doubt give rise to rich physics."