Although the concept of "steering" in quantum mechanics was proposed back in 1935, it is still not completely understood today. Steering refers to the ability of one system to nonlocally affect, or steer, another system's states through local measurements. The two systems are entangled, but it is an especially strong type of entanglement in which the systems are not just correlated, but correlated in a specific direction. Schrödinger originally proposed the concepts of entanglement and steering in response to a well-known Einstein-Podolsky-Rosen (EPR) paper that criticized quantum mechanics.
Since then, steering has only been experimentally demonstrated using inequalities, which involve testing whether or not systems obey the local hidden state model. Entangled systems that can steer each other violate the steering inequalities because they do not obey the local hidden state model. A disadvantage of these demonstrations is that they usually require many measurement settings, which weakens the tests.
In a new study published in Physical Review Letters, a team of physicists led by Professors Jin-Shi Xu and Chuan-Feng Li at the University of Science and Technology of China in Hefei; along with Jing-Ling Chen at Nankai University in Tianjin, China, and the National University of Singapore, have experimentally demonstrated EPR steering using a new method that requires fewer measurements and provides a stronger validation of steering.