Long-Lived Coherence on a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">μ</mml:mi><mml:mi>Hz</mml:mi></mml:mrow></mml:math> Scale Optical Magnetic Quadrupole Transition
V. Klüsener, Sebastian Pucher, Dimitry Yankelev, Jan Trautmann, F. Spriestersbach, Dmytro Filin, S. G. Porsev, M. S. Safronova, Immanuel Bloch, Sebastian Blatt
Abstract
We report on the coherent excitation of the ultranarrow ^{1}S_{0}-^{3}P_{2} magnetic quadrupole transition in ^{88}Sr. By confining atoms in a state insensitive optical lattice, we achieve excitation fractions of 97(1)% and observe linewidths as narrow as 58(1) Hz. With Ramsey spectroscopy, we find coherence times of 14(1) ms, which can be extended to 266(36) ms using a spin-echo sequence. We determine the lifetime of the ^{3}P_{2} level for spontaneous emission of magnetic quadrupole radiation to be 110(31) min, confirming long-standing theoretical predictions. These results establish an additional clock transition in strontium and pave the way for applications of the metastable ^{3}P_{2} state in quantum computing and quantum simulations.