Kid Quantum is James Cullen, a member of the Legion of Super-Heroes in the 30th Century. He has the ability to create stasis fields. The original James Cullen appeared during Five Years Later continuity, which was later erased by Zero Hour. He was said to have been the first Legionnaire to die in combat. Instead, it was revealed that he was a group of shape-shifting Proteans who had gone into hiding.
In Reboot Legion continuity, James Cullen was born on Xanthu. They made him one of the first Legionnaires, but he was killed by Tangleweb. His sister Jazmin Cullen had a much longer Legion tenure. Kid Quantum was created by Tom Bierbaum, Mary Bierbaum, and David A. Williams, first appearing in Legion of Super-Heroes (Volume 4) #33. (1992)