Defects promise quantum communication through standard optical fiber | 10/1/2018 | Staff
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An international team of scientists led by the University of Groningen's Zernike Institute for Advanced Materials created quantum bits that emit photons that describe their state at wavelengths close to those used by telecom providers. These qubits are based on silicon carbide in which molybdenum impurities create color centers. The results were published in the journal npj Quantum Information on 1 October.

By using phenomena like superposition and entanglement, quantum computing and quantum communication promise superior computing powers and unbreakable cryptography. Several successes in transmitting these quantum phenomena through optical fibers have been reported, but this is typically at wavelengths that are incompatible with the standard fibers currently used in worldwide data transmission.

Physicists - University - Groningen - Netherlands - Colleagues

Physicists from the University of Groningen in the Netherlands, together with colleagues from Linköping University and semiconductor company Norstel AB, both in Sweden, have now reported the development of a qubit that transmits information on its status at a wavelength of 1,100 nanometers. Furthermore, the mechanism involved can likely be tuned to wavelengths near those used in data transmission (around 1,300 or 1,500 nanometers).

The work started with defects in silicon carbon crystals, explains Ph.D. student Tom Bosma, first author of the paper. "Silicon carbide is a semiconductor, and much work has been done to prevent impurities that affect the properties of the crystals. As a result, there is a huge library of impurities and their impact on the crystal." But these impurities can form what are known as color centers, and these respond to light of specific wavelengths.

Lasers - Light - Energy - Color - Centers

When lasers shine light at the right energy onto these color centers, electrons in the outer shell of the molybdenum atoms in the silicon carbide crystals are kicked to a higher energy level. When they return to the ground state, they emit their excess energy as a photon. "For molybdenum impurities, these...
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