We communicate with each other using particles. Calls and messages ride on waves of light, websites and photos are loaded on electrons. All communications are inherently physical. Information is recorded and transmitted to real objects, even if we do not see them. Physicists also connect to the world when they communicate with it. They send flashes of light in the direction of particles or atoms and wait for the light to come back. Light interacts with particles of matter, and changing the behavior of light sheds light (excuse the pun) on the properties of particles - although these interactions often change particles as well. The process of this communication is called measurement.
The particles even bind together using other particles. The force of electromagnetism between two electrons is transferred by matter particles and quarks, which huddle inside the proton as they exchange gluons. Physics essentially studies interactions.
Information is always transmitted through interactions, between particles or with itself. We ourselves are made up of particles that communicate with each other, and we learn about our environment by interacting with it. The better we understand this interaction, the better we understand the world and ourselves.
Physicists already know that interactions are local. Like urban politics, the influence of particles is limited to their immediate surroundings. However, interactions are extremely difficult to describe. Physicists have to treat particles with respect and add complex terms to their lonely existence in order to simulate relationships with other particles. The resulting equations cannot be resolved. Therefore, physicists only have to roughly estimate single particles. Yet measuring the interactions of atomic and subatomic particles has created the most accurate field of physics of all.
Quantum mechanics is a complete theory of particles, describing their measurements and interactions. Over the past few decades, as computers began to master quanta, this theory has expanded to include information as well. The implications of quantum mechanics for the measurements and interactions of particles are extremely strange. Its implications for information are even stranger.
One of the strangest consequences disproves the material basis of communication, as well as common sense. Some physicists believe that we may be able to communicate without transferring particles. In 2013, enthusiastic physicist Hatim Salih even developed a protocol, along with professionals, in which information is obtained from a place that the particle has never traveled to. Information can be ethereal. Communication, it turns out, may not be so physical.
Last April, a short article on the Salih protocol appeared in the Proceedings of the National Academy. Most of the submitted authors of the work were members of the University of Science and Technology of China in its branches in Shanghai and Hefei. The last author was Jiang-Wei Pan, an eminent physicist who developed a constellation of communication satellites using quantum mechanics. He recently used his network to transmit entangled particles over 1200 kilometers.
Pan and his colleagues give out about work a month. But the document they published in April, co-authored by Yuan Cao and Yu-Huai Li, was exceptional. They described an experiment in which they sent a black and white image of a Chinese knot without transmitting a single particle.
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Extraordinary claims require extraordinary evidence - even if they are doubted by the person whose claims were based on the work of the group of scientists, Lev Weidman. Weidman and others have tried to interpret these results for ten years. We may be misunderstanding quantum theory.
Physicists struggle to decipher what quantum mechanics says about reality and about the material world. But this theory is just beginning to speak. Physicists are now questioning the uncertainty that comes from quantum theory, because even very weak measurements reveal information that was once considered secret. At stake are the very concepts of measurement and interaction, as well as the foundations of the information technology of the future.
ILYA KHEL