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Not enough spending

8LT315F15PD-LC_Datasheet PDF

Not enough spending

Mark LaPedus is editor-in-chief of Silicon Strategies, a sister Web site to EE Times.

8LT315F15PD-LC_Datasheet PDF

Vienna, Austria – The ability of elementary particles to become entangled quantum mechanically has been proposed as the basis for a new type of optical-fiber communication system. By demonstrating the same effect in a free-space optical communications system, a research group at the University of Vienna here may have found a way to greatly extend the range of optical quantum communication systems.

Experiments with the effect in fiber-optic systems have been successful up to distances of about 10 kilometers (6.2 miles), and theoretical calculations place an upper limit of 100 km (62 miles) on photon entanglement. It appears that the free-space version of quantum communication will be limited only by line-of-sight considerations, the researchers concluded in a recent report in Science.

Their proposal is to use a satellite network to create a global quantum communication system. The satellites could perform direct line-of-sight free-space communication with the ground and with one another. That type of global quantum-optical network is somewhat in the future in terms of technical implementation, as are the quantum computers that would benefit from it, but the concept now seems at least physically feasible.

8LT315F15PD-LC_Datasheet PDF

The researchers set up an emitter that produces two photons in exactly opposite polarization states, though the state of each photon is not known. Two receiving stations 600 meters apart intercepted the photons and measured their polarization. While the polarization state of the photons at one of the detector stations appeared as a random sequence, the corresponding measurements at the other station revealed a high correlation between the two sets of data-enough to verify that the photons shared the same quantum state over their entire journey.

In the near term, entangled photons are being used to develop absolutely secure communication systems. If a cryptographic key encoded with entangled photons were intercepted and read by an eavesdropper, the correlations typical of quantum entanglement would be destroyed and the act of eavesdropping detected.

8LT315F15PD-LC_Datasheet PDF

One problem with quantum encoding is that any attempt to read out information will destroy the quantum state. Therefore, it would be advantageous to have networks that allowed quantum computers to exchange information without actually reading it.

In the musical Les Miserables, the prisoners learn to look downward to avoid making eye contact with their brutal captors. In today's brutal market, networking-chip vendors have also learned to look downward to survive.

During the boom, too many companies launched programs to develop network processors, traffic managers, security processors and switch fabrics for 10- and even 40-Gbit/second line cards. With little or no market for such devices today, these vendors are now scrambling to retarget their chips for lower line speeds.

Just last year, IBM, for example, was touting the terabit scalability of its switch-fabric architecture. At NPC East 2003, the company instead introduced a fabric for systems with a total bandwidth of 20 Gbits/s, a speed that used to represent a single line card. IBM's PowerPRS C192 is aimed at systems with up to eight OC-48 ports.


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