  In this talk, I present the recent theoretical results on the electrical
conductivity (EC) sigma of quark matter, using the Kubo formula at finite
temperature and zero quark density (T>0, mu=0) in the presence of an external
strong magnetic field. The dilute instanton-liquid model with the caloron
distribution is taken into account. It turns out that sigma=(0.02~0.15)/fm for
T=(0~400) MeV with the relaxation time tau=(0.3~0.9) fm. EC is parameterized as
sigma/T (0.46,0.77,1.08,1.39)C_EM for tau=(0.3,0.5,0.7,0.9) fm, respectively.
These results are well compatible with other theoretical estimations and show
almost negligible effects from the magnetic field. The soft photon emission
rate from the quark-gluon plasma is discussed as well.
