Traveling without moving: Quantum communication scheme transfers quantum states without transmitting physical particles

While Einstein considered quantum entanglement as "spooky action at a distance," and those who fully accept entanglement acknowledge it to be counterintuitive, current entanglement-based quantum communication schemes for transferring an unknown quantum state from one place to another require classical transportation of particles between sender and receiver. Now consider this: Recently, scientists in China at Harbin Institute of Technology, Yanbian University and Changchun University demonstrated what is known as a counterfactual approach in which quantum information can be transferred between two distant participants without sending any physical particles between them. The researchers accomplished this by entangling two nonlocal qubits with each other without interaction – meaning that the present scheme can transport an unknown qubit in a nondeterministic manner without prior entanglement sharing or classical communication between the participants. Moreover, the scientists state that their approach provides a new method for creating entanglement that allows two qubits to be entangled without interaction between them.

Prof. Shou Zhang discussed the paper that he and his colleagues published in Scientific Reports. "There's a long-held assumption in the classical information field that information transfer requires physical particles to travel between sender and receiver – an assumption first challenged in 2013 by Hatim Salih and his colleagues¹," Zhang tells Phys.org. By using the so-called chained quantum Zeno effect, the 2013 paper showed how information can in fact be transferred between two locations without any physical particles traveling between them. (In the quantum Zeno effect, time evolution caused by quantum decoherence in quantum systems is suppressed by, for example, continuous observation or measurement, interaction with the environment, or stochastic fields. In a chained quantum Zeno effect, a series of secondary splitter/detector loops ensure that there is never a significant probability of decoherence.) "This mind-boggling and highly counterintuitive communication protocol inspired us to think whether quantum information can be transferred counterfactually," Zhang adds, "so in fact, our present scheme can be considered as an incremental extension of Salih's work from classical bit to quantum bit."