  Acoustic waves at microwave frequencies have been widely used in signal
processing applications. They are also emerging as a promising approach for
communication and manipulation of quantum information. However, dynamic control
of acoustic waves in a low-loss and scalable manner remains an outstanding
challenge, which hinders the development of phononic integrated circuits. Here
we demonstrate electrical control of traveling acoustic waves on an integrated
lithium niobate platform at both room and cryogenic temperatures. We
electrically tune the material elasticity to modulate the phase and amplitude
of the acoustic waves and demonstrate an acoustic frequency shifter by
serrodyne phase modulation. Furthermore, we show reconfigurable nonreciprocal
modulation by tailoring the phase matching between acoustic and quasi-traveling
electric fields. Our scalable electro-acoustic platform comprises the
fundamental elements for arbitrary acoustic signal processing and manipulation
of phononic quantum information.
