Using a two-electron spin qubit to detect electrons flying above the   Fermi sea
  We investigate experimentally the capacitive coupling between a two-electron spin qubit and flying electrons propagating in quantum Hall edge channels. We demonstrate that the qubit is an ultrasensitive and fast charge detector with the potential to allow single shot detection of a single flying electron. This work opens the route towards quantum electron optics at the single electron level above the Fermi sea. 
R. Thalineau, A.D. Wieck, C. B\"auerle and T. Meunier
cond-mat.mes-hall