Submillihertz magnetic spectroscopy performed with a nanoscale quantum sensor

Simon Schmitt, Tuvia Gefen, Felix M. Stürner, Thomas Unden, Gerhard Wolff, Christoph Müller, Jochen Scheuer, Boris Naydenov, Matthew Markham, Sebastien Pezzagna, Jan Meijer, Ilai Schwarz, Martin Plenio, Alex Retzker, Liam P. McGuinness^*, Fedor Jelezko