Heinz Barwich (22 July 1911 – 10 April 1966) was a German nuclear physicist who later defected to the United States-led Western Bloc in 1964.

Heinz Barwich was born in Berlin, Germany, into a "working middle class" family on 22 June 1911.: 76 [2] His father, Franz, was a bookkeeper and a political supporter for the cause of anarcho-syndicalism on the German Free Workers' Union platform.

: 2  After attending the physics lecture with Gustav Ludwig Hertz, he switched to study physics and graduated with bachelor's degree in 1934.: 2 Barwick worked on the isotope separation under Hertz at the Technical University of Berlin and submitted his doctoral thesis on the topics of the separation of gas mixtures by diffusion in flowing mercury vapor.

The objectives of their pact were threefold: Before the end of World War II, Thiessen, a member of the Nationalsozialistische Deutsche Arbeiterpartei, had Communist contacts.

In addition to Barwich's leftist political views, he stated that he was motivated to go to work in the Soviet Union as he was 33 years old, married, had three small children with a fourth on the way, and unemployed.

In October 1948, Gustav Hertz, Peter Adolf Thiessen, and Barwich were sent to a classified location to advise on problems related to the startup of the gaseous diffusion plant D-1.

Because of the milk drink kefir they were served daily during their lengthy stay, they christened the place Kieferstadt (Kefirstadt); the location was Verkh-Nejvinskij, and it was known as Sverdlovsk-44 within the Soviet atomic bomb project.

[16][17][18][19][20] In 1951, after the test of the first Soviet uranium atomic bomb, Hertz, Barwich, and Krutkov were awarded a Stalin Prize, second degree, for their work on gaseous diffusion isotope separation.

In 1956, he became director of the Zentralinstitut für Kernforschung (ZfK, Central Institute for Nuclear Research) and ordinarius professor at the Technische Hochschule Dresden.

At the ZfK, Barwich's main objectives were to build and put into operation the first nuclear reactor of the German Democratic Republic (GDR), which was purchased from the Soviet Union, and to establish a research institute.

He was also appointed to the Council of Scholars of the Joint Institute for Nuclear Research (Объединённый институт ядерных исследований, OIYaI) in Dubna, Soviet Union.