Storage techniques and light recovery

American physicists are now able to burn a synchronized pulse of light into a set of supercooled atoms - and then restore that same pulse of light from a collection of second atoms that way. a certain distance. Experiments have shown that macroscopic particles are difficult to distinguish explicitly as quantum mechanics says although they can be physically separated.

The experiment was conducted using Bose Eistein condensing atoms (BEC) cooled to temperatures that all of them were in the same quantum state (according to a paper published in the journal Nature).

To capture " jumping " light from one place to another, Lene Hau and his colleagues at Harvard University have exploited a technique they developed since 2001 to keep the pulses of light in Bose condensation state- Einstein, could make the laser light go so slow that it almost stopped. This technique involves projecting a pulse from a laser transmitter into the BEC atoms in the BEC state, inducing the distribution of small vibrations of the charge in the atom.

Physicist Lene Vestergaard Hau uses tiny lasers and clouds
to cover the supercooled atom makes light go so slow that it almost stops.
(Photo: msnbcmedia.msn.com)

Normally, the dipoles will emit and rapidly decay, but when projecting a controlled laser beam into the specialists, they will convert the oscillations in the electron into vibrations of the spin that are stable. than. Therefore, when this laser pulse is turned off, the information of the laser transmitter will be recorded on the oscillation of the spin dip of the atom. Reverse the control laser to release light, allowing the atoms to re-combine (for example, synchronizing with the original probe pulse).

The difference in the new technique is that the pulse is slowed to recreate at the BEC position about 1.6 mm away. The "trick trick" here is that the wave function of spin dipoles is actually a superposition of atoms in the ground state and in the spin excited state. Thanks to the principle of conservation of momentum, spin-excited atoms move from BCE initially when the atom absorbs the photon from the laser pulse, while the atoms in the ground state stand still at the position. there.

The information content of the probe pulse has been "imprinted" on the rotation of the dipoles of the first BEC atom (above) . In this new experiment, the barrier is made to appear a second BEC far away from 160 µm (below) - (Photo: Physicsweb.org)

One creative point is that the Harvard team decided to wait until the spin-excited atom went to the second condensate before re-applying the control lasers. And they realized that this set of physically separated atoms could then re-emit the original light. This restored light propagates slowly from the second BEC position before reaching the speed of 300,000 km / s as it is in light.

Because the two BEC positions were created completely independently, we can expect the sending of wave bundles from the first position to a second BEC strange location. In fact, it is not true that the ground-state wave function has an element on both BEC locations at the same time so that it can combine with the spin-excited component when it reaches the second position. The experiment is a powerful demonstration of quantum irrespective."By manipulating matter to reproduce the original light of the original light, we can use it in optical information processing," Hau said. She told Physics Web that the experiment could lead to optical information processing techniques in optical telecommunications and quantum information networks. Another application might be a super sensitive rotary sensor or gravitational detetor.

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