  Measurements of polarized neutron scattering were performed on a $S=1/2$
chain multiferroic LiCu$_2$O$_2$. In the ferroelectric ground state with the
spontaneous polarization along the c-axis, the existence of transverse spiral
spin component in the $bc$-plane was confirmed. When the direction of electric
polarization is reversed, the vector spin chirality as defined by ${\bf C}_{ij}
= {\bf S}_i \times {\bf S}_j$ ($i$ and $j$ being the neighboring spin sites) is
observed to be reversed, indicating that the spin-current model or the inverse
Dzyaloshinskii-Moriya mechanism is applicable even to this
$e_{\mathrm{g}}$-electron quantum-spin system. Differential scattering
intensity of polarized neutrons shows a large discrepancy from that expected
for the classical-spin $bc$-cycloidal structure, implying the effect of large
quantum fluctuation.
