  Coherent electron displacement is a conventional strategy for processing
quantum information, as it enables to interconnect distinct sites in a network
of atoms. The efficiency of the processing relies on the precise control of the
mechanism, which has yet to be established. Here, we theoretically demonstrate
a new route to drive the electron displacement on a timescale faster than that
of the dynamical distortion of the electron wavepacket by utilizing attosecond
single-cycle pulses. The characteristic feature of these pulses relies on a
vast momentum transfer to an electron, leading to its displacement following a
unidirectional path. The scenario is illustrated by revealing the
spatiotemporal nature of the displaced wavepacket encoding a quantum
superposition state. We map out the associated phase information and retrieve
it over long distances from the origin. Moreover, we show that a sequence of
such pulses applied to a chain of ions enables attosecond control of the
directionality of the coherent motion of the electron wavepacket back and forth
between the neighbouring sites. An extension to a two-electron spin state
demonstrates the versatility of the use of these pulses. Our findings establish
a promising route for advanced control of quantum states using attosecond
single-cycle pulses, which pave the way towards ultrafast processing of quantum
information as well as imaging.

Quantum Physics