  We theoretically discuss the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction
between semiconductor quantum dots (QDs). When each QD having a local spin is
coupled to the conduction electrons in semiconductors, an indirect exchange
interaction, i.e., the RKKY interaction, is induced between two local spins.
The RKKY interaction between QDs, which is mediated by the Fermi sea in
semiconductors, is modulated by changing the Fermi energy, and the magnitude or
even the sign of the exchange interaction can be tuned, which leads to a
tunable magnetic transition in QD devices. We estimate the magnitude of the
RKKY interaction in QDs as a function of the electron density and the inter-dot
distance.
