Entangled light-emitting diode (ELED)An entangled LED is a light-emitting diode containing a quantum dot that enables the production of entangled photons (light particles) on demand. According to researchers at Toshiba labs, where the device was developed, ELEDs could be used to create an optical quantum computer capable of performing in seconds tasks that would take a high-end conventional computer years to complete.

An LED is a semiconductor device that emits visible light when an electric current passes through it. The ELED is similar to a semiconductor LED but, with the application of an electrical charge, emits entangled photons. Although entangled LEDs have previously been created with lasers, the equipment required is too bulky and complex to be practical for quantum computing applications. The compact and simple nature of entangled LEDs make it possible to include large numbers of electronically addressable entangled light emitters on a single chip.

Entanglement is a phenomenon of quantum mechanics in which particles can become correlated to predictably interact with each other regardless of how far apart they are separated. If one entangled particle's spin state (the direction of its spin) is measured, we know that the spin of its mate is in the opposite direction. Harnessing that capacity could yield the enormous increase in processing power expected from quantum computing.

Other potential applications for entangled LEDs include quantum cryptography.

quantum dotA quantum dot is a particle of matter so small that the addition or removal of an electron changes its properties in some useful way. All atom s are, of course, quantum dots, but multi-molecular combinations can have this characteristic. In biochemistry, quantum dots are called redox groups. In nanotechnology , they are called quantum bits or qubit s. Quantum dots typically have dimensions measured in nanometers, where one nanometer is 10 -9 meter or a millionth of a millimeter.

The fields of biology, chemistry, computer science, and electronics are all of interest to researchers in nanotechnology. An example of the overlapping of these disciplines is a hypothetical biochip , which might contain a sophisticated computer and be grown in a manner similar to the way a tree evolves from a seed. In this scenario, the terms redox group and qubit are equally applicable; it is hard to classify such a chip as either animate or inanimate. The quantum dots in a biochip would each account for at least one data bit, and possibly several.

In the extreme, the position of a single electron in a quantum dot might attain several states, so that a quantum dot could represent a byte of data. Alternatively, a quantum dot might be used in more than one computational instruction at a time. Other

applications of quantum dots include nanomachines , neural networks, and high-density memory or storage media.

quantum cryptography

- Quantum cryptography uses our current knowledge of physics to develop a cryptosystem that is not able to be defeated - that is, one that is completely secure against being compromised without knowledge of the sender or the receiver of the messages. The word quantum itself refers to the most fundamental behavior of the smallest particles of matter and energy: quantum theory explains everything that exists and nothing can be in violation of it.

Quantum cryptography is different from traditional cryptographic systems in that it relies more on physics, rather than mathematics, as a key aspect of its security model.

Essentially, quantum cryptography is based on the usage of individual particles/waves of light (photon) and their intrinsic quantum properties to develop an unbreakable cryptosystem - essentially because it is impossible to measure the quantum state of any system without disturbing that system. It is theoretically possible that other particles could be used, but photons offer all the necessary qualities needed, their behavior is comparatively well-understood, and they are the information carriers in optical fiber cables, the most promising medium for extremely high-bandwidth communications

semiconductor

- A semiconductor is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. Its conductance varies depending on the current or voltage applied to a control electrode, or on the intensity of irradiation by infrared (IR), visible light, ultraviolet (UV), or X rays.

The specific properties of a semiconductor depend on the impurities, or dopants, added to it. An N-type semiconductor carries current mainly in the form of negatively-charged electrons, in a manner similar to the conduction of current in a wire. A P-type semiconductor carries current predominantly as electron deficiencies called holes. A hole has a positive electric charge, equal and opposite to the charge on an electron. In a semiconductor material, the flow of holes occurs in a direction opposite to the flow of electrons.

Elemental semiconductors include antimony, arsenic, boron, carbon, germanium, selenium, silicon, sulfur, and tellurium. silicon is the best-known of these, forming the basis of most integrated circuits (ICs). Common semiconductor compounds include gallium arsenide, indium antimonide, and the oxides of most metals. Of these, gallium

arsenide (GaAs) is widely used in low-noise, high-gain, weak-signal amplifying devices.

A semiconductor device can perform the function of a vacuum tube having hundreds of times its volume. A single integrated circuit (IC), such as a microprocessor chip, can do the work of a set of vacuum tubes that would fill a large building and require its own electric generating plant.