Switching properties of a T-shaped quantum waveguide are studied by so
lving the two-dimensional time-dependent Schrodinger equation under co
ntinuous injection. Assuming a ballistic electron transport, the condu
ctance transient alternately overshoots and undershoots the steady-sta
te value and shows a self-sustaining harmonic oscillation in the long-
time limit. Analysis by Fourier transform resolves the various spectra
l contributions in the terahertz range and it is found that the quantu
m system keeps a memory of its initial state at short times. Pronounce
d mixing effects are shown with an electron wave function shared betwe
en the bound and metastables states of the initial and final eigenspec
tra. (C) 1997 American Institute of Physics.