Scientists from the universities of the American states of Maryland and Michigan, under the leadership of Stephen Olmshenko, were able to transfer a quantum state from one ytterbium ion to another, located at a distance of one meter, using several photons and the phenomenon of quantum entanglement exchange between particles. So far, the efficiency of the process used is very low – out of a billion attempts, on average, only 22 end in state transfer, but in the future such a process will help build quantum networks – in your hypothetical quantum computer, it is more convenient to write information in the state of particles, and it is better to transmit it over a long distance using quanta Sveta.
Quantum teleportation does not involve physical movement of a particle, it is only a transfer of its quantum state. However, since all identical particles are fundamentally indistinguishable, and the quantum state determines all its properties, the transfer of state is equivalent to movement. In principle, no one bothers to transfer from one teleport to another, say, a sandwich with sausage, if it does not measure itself on itself: after all, a sandwich is a state of a very large system of electrons, protons and neutrons. True, so far there is no need to dream about the technical possibility of such teleportation. Moreover, there is a theorem about the impossibility of quantum cloning, and in order to teleport the sandwich state of one system of particles, you will have to destroy the first sandwich.
American scientists prepared two ions in two separate traps, the unknown state of one of which had to be transferred to the other, which was initially in a known state. After that, two laser pulses caused the ions to emit two photons, the energy of which depends on the initial state of the ion. Since initially one of the ions was in an unknown state, then one of the photons is also in an unknown state. However, due to the unambiguous connection between the photon energy and the state of the ion, the photon and the ion are entangled – there is no such state of two particles separately, which would be equivalent to the state of their system as a whole.
Then two photons were sent through the optical fibers to the interferometer, where a measurement was carried out above them, which did not separate the two particles (in fact, due to the need to carry out a simultaneous measurement, the efficiency of the process is so low). In this case, entanglement is transferred from the ion-photon system to the ion-ion system. Well, then a standard protocol is used – a measurement is made over the transmitted ion, and, depending on its result, a correction is applied to the second ion (irradiation with a photon of a certain frequency), after which it appears in the initial state of the first ion. It is the last step that is described in the new work – everything else was demonstrated earlier, but it took almost a year and a half to implement and confirm it.
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