  To combine the advantages of ultrafast femtosecond optics with an on-chip
communcation scheme, optical signals with a frequency of several hundreds of
THz need to be down-converted to coherent electronic signals of GHz or less. So
far, this has not been achieved because of the impedance mismatch within
electronic circuits and their overall slow response-time. Here, we demonstrate
that 14 fs optical pulses in the near-infrared (NIR) can drive electronic
on-chip circuits with a bandwidth up to 10 THz. The corresponding electronic
pulses propagate in microscopic striplines on a millimeter scale. We exploit
femtosecond photoswitches based on tunneling barriers in nanoscale metal
junctions to drive the pulses. The non-linear ultrafast response is based on a
combination of plasmonically enhanced, multi-photon absorption and quantum
tunneling, and gives rise to a field emission of ballistic electrons
propagating across the nanoscale junctions. Our results pave the way towards
femtosecond electronics integrated in waferscale quantum circuits.
