Quantum Theory and technology

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Nuclear reactors


Nuclear reactors, based on the controlled use of nuclear fission, have been used to generate electricity since the 1950's. The image shows four light bulbs lit with electricity generated from the first nuclear power plant located near Arco, Idaho, that was activated on December 20, 1951. The site is now a United States National Historic Landmark.



The transistor is an electronic device made from semiconductor materials. A semi-conductor is a solid whose electrical conductivity lies between that of a true conductor and an insulator. Its behaviour is determined by the quantum mechanical properties of electrons. The widespread use of transistors in many types of electrical devices (for example, computers, cell phones, and digital audio players) make it one of the most important inventions of the 20th century.

The image shows a replica of the first transistor invented at Bell labs in 1947. Since then, transistors have been dramatically reduced in size to the extent that nowadays a single computer chip can contain hundreds of millions of transistors.



A laser is a quantum mechanical device that emits light with a well-defined wavelength in a very narrow beam. The operation of a laser is based on the quantum mechanical process of stimulated emission, predicted by Einstein when he studied the photoelectric effect. The first lasers were made in 1960 and since then their use has become widespread, for example in compact disc and DVD players, for cutting metals in manufacturing, and in medicine.

Photovoltaic cells


A photovoltaic cell (also known as a solar cell) is a device that converts light energy into electrical energy, by exploiting the quantum mechanical properties of electrons. Arrays of photovoltaic cells are increasingly being used to generate electric power from sunlight, for example, for residential use, and for space probes and the International Space Station.

Electron microscopes


An electron microscope uses a beam of electrons instead of light to create an image with a magnification factor of up to two million (compared to two thousand for a light microscope). The quantum mechanical principle on which the electron microscope is based is the wave-particle duality for electrons.

Magnetic Resonance Imaging (MRI)

MRI photo of a human head

MRI uses the quantum mechanical magnetic properties of an atom's nucleus (referred to as nuclear magnetic resonance) to create an image of the interior of an object. A common use is in medical imaging, i.e. creating images of the interior of the human body in order to help with medical diagnosis.

Charge-Coupled Devices (CCD)

Charge-coupled device

A CCD uses charges generated via the photoelectric effect to create digital images. They are used extensively in digital cameras, and have revolutionized the recording of observations in astronomy (for example, they have enabled astronomers to make surveys of distant galaxies). CCDs capture 70% or more of the photons hitting the photoreactive surface (they have a quantum efficiency of 70%), while photographic film captures only about 2%.