Light into the dark quantum calculation

In "Dark States" Prisoner Photons could show the way to realizing a quantum computer

Constructing a quantum computer is one, albeit not ancient, humanity dream. Bits (QBITS) stored in quantums are superior to the incoming zeros and inheritance of the binary age: quantum compression can be molten and superimpose, which makes massively parallel processing for natural computing travel. Over speed gain, new applications, generally a new theory of predictability, can only be speculated.

If you might build a quantum computer, however, has a problem: how do you save quantum attack permanently and stable? Take as an example of a quantum bit, a quBit the polarization of a photon. The photon can be polarized to exactly two ways, the polarization can be easily adjusted and measure later – perfect. But there is a difficulty: the photon does not stay on the spot, but moves with the speed of light through the area. However, if one starts, we say with the help of a CCD element, the absorption is lost the information about the quantum state – the qubit is desorted.

But is the speed of light a problem? No, because already in 1999, the physicist Lene Hau succeeded in Harvard University, light pulses to brakisk to the speed of a cyclist, and in 2001 was light of her "hedged". Is now the speed of light C = 0 ? Not quite; which is actually happening is that the information about the modulation of a light pulse of some microseconds duration, and thus a long by a few kilometers, is held in a cloud of sodium atoms, which is roughly a tenthmillimeter.

Lene Hau in Harvard Gazette of 24.01.01

The realization sees in principle: a number of atoms in the energetically lowest state (basic state) is illuminated by two laser beams, the so-called "coupling beam" and the "signal beam". The coupling of the "signal beam" To the illuminated atoms, it creates a quantum mechanical shift – "Dark State" (Dark condition) called. Of the "coupling beam" ensures that the composition can not decay again. The speed of the light pulse takes place (as in a visually dense medium with high refractive index).

The absolutely striking happens when you have the "coupling beam" Dumpling: The weaker whose intensity, the slower seems that "signal beam" to move, and if the "coupling beam" is switched off, the "signal beam" Completely captured and "hold on"! You drive the "coupling beam" then again, leaving the "signal beam" The nuclear cloud again, more precisely, based on the atomic state – in which the information of the "Signal beams" still exists – an identical light pulse is generated. This conceptually hardly to be detected possibility of controlling light, let the realization of a quantum computer appear possible.

Like the Schildburger: capture light

Hunting on this journey, such as the magazine New Scientist in its edition of 22. May 04 reported, next to Ha and her colleagues a series of research teams, including Jeff Kimble at California Institute of Technology (Caltech). There it was even managed to store and read out individual photons (in ultra-old casium), especially to separate the noise from the signal and to detect the correlation between them individually.

Another approach is followed by Mikhail Lukin, also from Harvard University. Lukin experimented with two "Coupling beams", which he brought to interference, so that amplifier and decomposition zones changed together. For the "signal beam" The zones meant complete coupling to the atoms of the gas (speed zero) and release in the intermediate areas. It formed standing waves – really and true "captain". The next step goods, several "Signal beams" to use and find out if they can be controlled to interact in order to actually achieve information processing.

There is still the "Latch" Difficult to realize

One of the many difficulties in the realization of the quantum computer on this path is of course that the storage media, the low temperature gas clouds (which remain gas-forming only at extremely deep prere, so a vacuum chamber need) are not as right for mass production. But there are evidence that the phanomena in crystals can be produced as well, so it remains an approach with realization potential. Apart from that, the possibility of warranted quantum emergence offers permanently stable, still completely different outlooks, for example for high-priced time life at the University of Bonn.

Both "Dark States" are still many surprises to be expected.

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