  We demonstrate the operation of a quantum ratchet in the absence of
dissipative processes within the observation time (Hamiltonian regime). An
atomic rubidium Bose-Einstein condensate is exposed to a sawtooth-like optical
lattice potential, whose amplitude is periodically modulated in time. The
ratchet transport arises from broken spatiotemporal symmetries of the driven
potential, resulting in a desymmetrisation of transporting Eigenstates (Floquet
states). The measured atomic current oscillates around a non-zero stationary
value at longer observation times, shows resonances at positions determined by
the photon recoil and depends on the initial phase of the drive, providing
different lines of evidence for the full quantum character of the ratchet
transport. The results provide a proof of principle demonstration of a quantum
motor.
