[2] In Bombay Kallianpur came in contact with D. D. Kosambi, a well-known mathematician and versatile scholar and with Subbaramiah Minakshisundaram at Andhra University which was then in Guntur.
Under the supervision of Herbert Robbins, of the Statistics Department of the University of North Carolina, Chapel Hill he obtained his doctoral degree in 1951 in the then developing field of stochastic processes.
In the start of his career he held the position of lecturer at the University of California, Berkeley, during 1951–52, and was a member of the Institute for Advanced Study, Princeton, from 1952 to 1953.
During the period distinguished scientists, like Ronald Fisher, Norbert Wiener and Yuri Linnik visited the Institute.
At University of Minnesota Kallianpur collaborated with Charlotte Striebel, a member of the Research Group of Lockheed Corporation working on filtering and control problems.