1. In recent years much attention has been paid to
entanglement, which is one of the most striking features of quantum mechanics.
The correlation between two systems can be used to test local hidden variable
theories against quantum mechanics (Bell 1967). Maximally entangled states of
three or more systems, referred to as Greenberger–Horne–Zeilinger (GHZ) states
(Greenberger 1989, 1990) allow a stronger test of local hidden variable theories
without using Bell’s inequalities. Besides the investigation of fundamental
aspects of quantum mechanics, entangled states are useful in fields involving
quantum information, such as quantum cryptography, quantum computation , and
quantum teleportation.
2. A scheme, based on the resonant atom–field interaction, has been proposed for preparing two two-level atoms in a maximally entangled state. Recently, such a scheme has been experimentally realised. It has also been shown that a GHZ state of three atoms can be generated using the resonant atom–field interaction if the field is initially prepared in a superposition of a three-photon state and the vacuum state (Cirac and Zoller 1994).
3. Other cavity QED methods have also been proposed for the preparation of multi-atom GHZ states. In a very recent paper, Sackett (2000) have reported experimental entanglement of four trapped ions using a new technique proposed.
4. On the other hand, three-photon GHZ entanglement has also been observed. Proposals have been suggested to entangle spatially separated cavities. As an intermediate step of teleportation, Davidovich (1994) have shown how to produce two-cavity entangled states, in which a single photon resides in either cavity. Using a combination of quantum switches Davidovich (1993) have proposed a scheme for the generation of the entangled coherent states (Sanders 1992a, 1992b) for two cavities. Kim and Lee (2000) have suggested a nonlocal test for entangled states of two spatially separated cavities.
Answer the question: What entangled states are useful for?
2. A scheme, based on the resonant atom–field interaction, has been proposed for preparing two two-level atoms in a maximally entangled state. Recently, such a scheme has been experimentally realised. It has also been shown that a GHZ state of three atoms can be generated using the resonant atom–field interaction if the field is initially prepared in a superposition of a three-photon state and the vacuum state (Cirac and Zoller 1994).
3. Other cavity QED methods have also been proposed for the preparation of multi-atom GHZ states. In a very recent paper, Sackett (2000) have reported experimental entanglement of four trapped ions using a new technique proposed.
4. On the other hand, three-photon GHZ entanglement has also been observed. Proposals have been suggested to entangle spatially separated cavities. As an intermediate step of teleportation, Davidovich (1994) have shown how to produce two-cavity entangled states, in which a single photon resides in either cavity. Using a combination of quantum switches Davidovich (1993) have proposed a scheme for the generation of the entangled coherent states (Sanders 1992a, 1992b) for two cavities. Kim and Lee (2000) have suggested a nonlocal test for entangled states of two spatially separated cavities.
Answer the question: What entangled states are useful for?
entangled states are useful in fields involving quantum information, such as quantum cryptography, quantum computation , and quantum teleportation.
ОтветитьУдалитьEntangled states are useful in fields involving quantum information, also they allow a stronger test of local hidden variable theories without using Bell’s inequalities. Османов
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