We consider an interacting, one-dimensional Bose gas confined in a split trap, obtained by an harmonic potential with a localized barrier at its center. We address its quantum-transport properties through the study of dipolar oscillations, which are induced by a sudden quench of the position of the center of the trap. We find that the dipole-mode frequency strongly depends on the interaction strength between the particles, yielding information on the classical screening of the barrier and on its renormalization due to quantum fluctuations. Furthermore, we predict a parity effect which becomes most prominent in the strongly correlated regime.PACS numbers: 05.30. Jp, 67.10.Jn, 03.75.Kk The study of elementary excitations is a fundamental aspect of many-body theories. For neutral quantum fluids, these excitations at low energy correspond to sound waves for homogeneous systems and to inhomogeneous collective modes with discrete frequencies for confined ones. The analysis of the latter in ultracold quantum gases has been the subject of intense experimental [1][2][3][4][5][6][7][8] and theoretical [9][10][11][12][13][14] activity in the last decades. A variety of different excitation modes has been characterized, as the monopole (breathing), dipole (sloshing), quadrupole, and scissor modes, to cite the best known. An unprecedented precision has been reached in the measurement of their frequencies, becoming one of the most reliable tests for theoretical models and tools to investigate many-body phases and beyond-mean field effects [2,[15][16][17]. One of the most interesting aspects of these excitations is that their frequencies depend on the microscopic properties of the system, yielding information e.g. on the equation of state or on its superfluid properties.The analysis of collective modes allows in particular to investigate the interplay between strong interactions and confinement in low-dimensional geometries [18][19][20][21]. In this work, we show that by using a specific confining geometry, i.e. a localized barrier at the center of a quasionedimensional harmonic trap, one can directly access the effect of quantum fluctuations, which play a major role in low dimensions. Effectively one-dimensional systems have been realized in ultracold-atoms experiments, by employing optical lattices to create arrays of tubes or by creating a single atomic waveguide on an atom chip [22][23][24][25]. Strongly correlated phases are more accessible in one-dimensional gases [26], where interparticle interactions may be tuned by confinement-induced resonances, and because, counterintuitively, in one dimension the interactions become dominant in the low-density regime where particle losses and three-body recombination effects are reduced. The demonstration of the peculiar fermionized Tonks-Girardeau phase constitutes a beautiful example [27,28].We focus on the dipolar excitation mode of a onedimensional (1D) ultracold Bose gas, i.e. on a periodic oscillation of the center of mass of the atomic cloud. In ultracold-gas experiments, ...