JÖrg Wrachtrup

Jörg Wrachtrup (born 27 December 1961) is a German physicist.

While working on his PhD thesis, he carried out the first electron spin resonance experiments on single electron spins.^[1] The work was done in close collaboration with and in the lab of M. Orrit at the CNRS Bordeaux. In the course of these studies also the first coherent experiments on single electron spins in a solid were successful. In subsequent investigations even electron nuclear double resonance which mark the first experiments on single nuclei has been achieved. While working at the Chemnitz University of Technology, he headed a research team that has, for the first time, detected the optical signal of a single defect center. The particular defect was the nitrogen-vacancy center (N-V) in diamond.^[2] This pioneering work has created standards for numerous follow-up studies of individual N-V centers aiming at manipulations of individual nuclear spins in solids (quantum computer). All of the above achievements combined the following essential elements:

• N-V centers were produced in sufficiently low concentrations, so that separation between the centers exceeded several micrometers, and individual centers could be detected using a "conventional" scanning confocal optical microscope.
• Photoluminescence and electron paramagnetic resonance techniques were combined into optically detected magnetic resonance, detected from a single center.

The authors of the paper being experience in single molecule magnetic resonance deliberately were choosing a defect center with an electron paramagnetic ground state. By this they achieved room temperature single electron spin resonance. In addition the defect center proved to be unconditionally photostable, in contrast to most other single quantum emitters. This discovery is the basis for numerous applications of defects in diamond as single photon source, quantum register and in magnetometry.

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