Quantum communication optical

Since the realization of the first laser 40 years ago, the merging of the fields of quantum electronics and quantum optics has stimulated the development of many new materials and devices. These, in turn, support a flourishing optoelectronics market for optical communications, optical data processing, medical diagnostics, materials processing, display technology, and many other applications. 

In Sect. 6.6 a proposal to implementing a QC based on optical cavity quantum electrodynamics is described (Pellizzari et al. 1995). The scheme is similar to the ion trap QC in the sense that the atomic quantum bits are resting in a trap. However, quantum communication is provided by photons instead of phonons. 

In optical domain, preamplifier is no more an utopia and is in actual use in fiber communication. However quantum physics prohibits the noiseless cloning of photons an amplifier must have a spectral density of noise greater than 1 photon/spatial mode (a "spatial mode" corresponds to a geometrical extent of A /4). Most likely, an optical heterodyne detector will be limited by the photon noise of the local oscillator and optical preamplifier will not increase the detectivity of the system. 

Heterodyne is a very efficient tool for detecting the phase of a "coherent" signal i.e. a signal which has a stable phase relation to the local oscillator. The detector is only limited by the quantum fluctuation of vacuum. This property is common use in coherent lidar. Satellite to satellite optical communications using laser as a local oscillator are under development (Fig. 3). 

The work described in this paper is an illustration of the potential to be derived from the availability of supercomputers for research in chemistry. The domain of application is the area of new materials which are expected to play a critical role in the future development of molecular electronic and optical devices for information storage and communication. Theoretical simulations of the type presented here lead to detailed understanding of the electronic structure and properties of these systems, information which at times is hard to extract from experimental data or from more approximate theoretical methods. It is clear that the methods of quantum chemistry have reached a point where they constitute tools of semi-quantitative accuracy and have predictive value. Further developments for quantitative accuracy are needed. They involve the application of methods describing electron correlation effects to large molecular systems. The need for supercomputer power to achieve this goal is even more acute. 

The creation of nanoscale sandwiches of compound semiconductor heterostructures, with gradients of chemical composition that are precisely sculpted, could produce quantum wells with appropriate properties. One can eventually think of a combined device that incorporates logic, storage, and communication for computing—based on a combination of electronic, spintronic, photonic, and optical technologies. Precise production and integrated use of many different materials will be a hallmark of future advanced device technology. 

Alice and Bob communicate via a quantum channel such as an optical fiber wire. 

It is conceivable that this diverse work on Si quantum dots could soon lead to a new generation of Si/Si].xGex optoelectronic devices at the optical fiber communication wavelengths of 1.3 and 1.55 pm. 

Recently, hopes have been raised for the use of CNTs as superior biosensor materials. Successful fabrication of various analytical nanotube devices, especially those modified with biomolecules, has made this a possibility. These prototype devices, sometimes prepared as ordered arrays or single-nanotube transistors, have shown efficient electrical communications and promising sensitivities required for such applications as antigen recognition,38 enzyme-catalyzed reactions39 and DNA hybridizations.40 Publications considering a quantum dot bahaviour of CNTs show their promise for biorecognition devices with optical indication.41... 

The calculation of the electric properties of individual molecules as found in an infinitely dilute gas has for long been of great interest to quantum chemists. This curiosity has been spurred in recent decades by the increasing importance of the communications industry in the world and the parallel need for materials having specific properties for electronic, optical, and other devices. In particular, the nonlinear-optical quantities, defined at the microscopic level as hyperpolarizabilities and at the macroscopic level as nonlinear susceptibilities, have played a... 

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