ScienceDaily (May 2, 2011) memory data could hardly be less than: researchers working with Gerhard Rempe at the Max Planck Institute of quantum optics in Garching has stored quantum information in a single atom. Scholars wrote the quantum state of a single photons, that is, the light particles into atomic rubidium, vrshm it again after a particular volume. This technique can be used in principle to design a powerful domain and to communicate them quantum with one another across large distances.
Quantum computers one day be able to cope with the computational tasks within a short time in which the current domain will take years. They would take the enormous computing power of their ability to simultaneously process diverse data items that are stored in the microscopic quantum physical systems, such as a single opaque vpotonim. In order to be able to run, you must replace these quantum computers are pieces of information between the various components. Photons are especially suitable to do this, as no matter what needs to be transported with them. Particulate matter however will be used for processing and storing information. Researchers are looking for and methods by which you can exchange information between photons and quantum. However already performed with ensembles of many thousands of atoms, physicists at the Max Planck Institute of quantum optics in Garching now proven that quantum information also can be controlled from a single photons to atoms.
Using a single atom that storage unit has several advantages: minimizes the extremists have only one, says Holger Specht mmboss-Garching Max-Max, which was involved in the experiment. You can process the information stored by direct manipulation baatom, which is important for performing logical operations, quantum computer. "In addition, it offers the opportunity to see if quantum information stored in the bapoton successfully written into the atom without destroying the quantum state," says Specht. Possible, make sure that you have to go early in the process of computing due to storage.
The fact that no one could very recently on quantum information exchanged between photons and atoms single was that interaction between the light particles and atoms very weak. Atom, the photon will not take notice of it, as it were, like two people barely speak to each other party, so replace only a little bit of information. Researchers in Garching have enhanced interaction with rotation. They assume the Atomic rubidium between optical resonator mirrors, and then use very weak laser pulses to introduce single photons into the cavity. Reflected photons in the cavity mirrors several times back and forth, which improved the interaction between photons and atom. Figuratively speaking, guests of the party and meet more often and increases the chance that they are talking to each other.
Photons carried quantum information in the form of polarization. This can be left (direction of rotation of the electric field is counterclockwise) or right (clockwise). Quantum state of the photon polarizations can be both at the same time as the superposition. Interact with the photon the atom rubidium is usually excited and then loses again the excitement of more probabilistic photon emission. Garching-based investigators did not want it to happen. On the contrary, the absorption of photon the atom could bring into the quantum state RB, steadily. The researchers at this with a laser beam, laser Control Panel, where they are directed to RB atom at a time when you interact with the photon.
Because the spin of the atom mabotiam contributes to stable quantum state generated by vapoton laser control. Spin gives the Atomic magnetic moment. Quantum state, the researchers use to store, and is determined by the orientation of the magnetic moment. The country is characterized by the fact that it reflects the State of polarization of a photon of the orientation: refers to the direction of the magnetic moment of the photon polarization cycle, a mixture of the two sides chshocmt being stored by the appropriate mixture of magnetic moments.
This is referred to as the reverse process: the Atomic rubidium with laser control panel again causes it to emit the photon re-which was the source of the event. The vast majority of cases, information Quantum Photon-out screens with information stored in the source, as physicists discovered in Garching. Quantity that describes this relationship, trust, was more than 90 percent. This is significantly higher than the 67 percent to fidelity can be reached with classical methods, that is not based on quantum effects. The method was developed in Garching is therefore a real quantum memory.
The physicists to measure the time storage, that is, the time quantum information may be retained, as RB-about 180 microseconds. "This is a parallel with times all quantum memories based on previous ensembles of atoms," says Stefan Ritter, a more involved in the experiment. Nevertheless, time is significantly more is required for the method used quantum quantum computer or network. There is also another quality characteristic of quantum memory in a single atom that can improve from Garching: efficiency. This is a measure of the number of photons are irradiated are stored, and then read again. It was just under 10 percent.
Storage time is mainly limited by the magnetic field fluctuations from the lab, said Ritter. "This is so you can zoom in by quantum information storage, quantum States of the atoms that they are sensitive to magnetic fields." effectiveness is limited by the fact that the atom to sit still in the center of the cavity, but passes. This causes the strength of the interaction between the atom photon to decrease. The researchers also helping improve the efficiency and effectiveness: by large cooling of the atom, that is, by its kinetic energy to another.
Researchers at the Max Planck Garching and now you want to work on these two improvements. "If this operation succeeds, the chances of a single Atom quantum memory is excellent," says Stefan Ritter. The interface between individual light atoms allow more quantum computer network atoms with this than be possible without such interface; The fact that such a machine to make stronger. Moreover, quantum mechanical photons will be possible across large distances and entangle atoms. Quantum entanglement is a type of mechanical link between the particles needed to transmit quantum information over large distances. It is currently in development at the Max Planck Institute of quantum optics, making that a critical element of the future "quantum Internet."
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The above story is published (with writers adaptations by a teamdaily science) materials provided by Max-Planck-Gesellschaft.
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- Holger p. Specht, Christian Nölleke, Andreas Reiserer Uphoff, Eden, Manuel Figueroa, Stefan Ritter, Gerhard Rempe. Single-Atom quantum memory. Nature, 2011; DOI: 10.1038/nature09997
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