[1] Carnegie Mellon Univ, Dept Comp Sci, Pittsburgh, PA 15206 USA
[2] Carnegie Mellon Univ, Robot Inst, Pittsburgh, PA 15206 USA
[3] Stanford Univ, Dept Biochem, Stanford, CA 94305 USA
[4] Stanford Univ, Dept Phys, Stanford, CA 94305 USA
[5] Seoul Natl Univ, Dept Elect & Comp Engn, Seoul 151741, South Korea