Excellent question, which is why I am happy to answer it by being as clear as possible in my explanations. First of all, before answering this question directly, I would like to explain what quantum entanglement is.
It must be said that this phenomenon defies understanding. Quantum entanglement refers to the existence of an invisible link between two particles that were emitted at the same time, regardless of the distance between them. In this way, if the state of one of them changes, that of its twin changes instantly, as if it were a single system.
“When you ‘touch’ one object of a pair of entangled objects, the second one quivers, despite the distance” , summarizes Nicolas Gisin , Swiss physicist and professor of physics at the University of Geneva. This phenomenon has been verified many times in the laboratory since the 1970s. Do not ask me how it is possible, scientists themselves have been tearing their hair out for decades to explain this phenomenon.
For now, we do not understand anything about this invisible link. But despite everything, understanding its mechanism, many researches have been undertaken in order to exploit this fabulous property in the fields of quantum information, such as quantum cryptography, quantum teleportation and quantum computer.
It exploits the principles of quantum entanglement to make a message incomprehensible to anyone who has intercepted it, except the person for whom it is intended.
Since it is impossible to clone entangled information without it being destroyed, or to measure a quantum state without modifying it, the reading of the information by an intruder would be immediately detected by the recipients of the message.
It is not a question here of actually teleporting objects or people as in Star Trek , but rather of setting up a communication protocol consisting in transferring the quantum state of a system to another system similar and spatially separated from the first by taking advantage of quantum entanglement.
A quantum computer is the equivalent of a classical computer, except that its calculations are performed at the atomic scale. It is based on the laws of quantum physics , which is concerned with the behavior of matter and light at the microscopic level.
At this scale, strange, totally counter-intuitive phenomena occur. An object can be in several states as long as it has not been measured: this is the principle of quantum superposition . And two objects can influence each other even when separated by a great distance: this is the principle of quantum entanglement.
Quantum entanglement is a fascinating area of research that never ceases to amaze and for which new fields of research will certainly emerge in the future.