Daniel M. Greenberger is an American

quantum In physics, a quantum (: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a property can be "quantized" is referred to as "the hypothesis of quantization". This me ...

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

. He has been

professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other tertiary education, post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin ...

of physics at the

City College of New York The City College of the City University of New York (also known as the City College of New York, or simply City College or CCNY) is a Public university, public research university within the City University of New York (CUNY) system in New York ...

since 1964. He is also a fellow of the

American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of ...

and—alongside Anton Zeilinger—founded the APS Topical Group on Quantum Information.

Biography

Daniel Greenberger graduated in 1950 from the

Bronx High School of Science The Bronx High School of Science is a State school, public Specialized high schools in New York City, specialized high school in the Bronx in New York City. It is operated by the New York City Department of Education. Admission to Bronx Science ...

. He then graduated in 1954 from

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

, where he conducted his thesis under Laszlo Tisza. He received his MS (1956) and

PhD A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...

(1958) from the

University of Illinois The University of Illinois Urbana-Champaign (UIUC, U of I, Illinois, or University of Illinois) is a public university, public land-grant university, land-grant research university in the Champaign–Urbana metropolitan area, Illinois, United ...

, where his advisor was Francis E. Low. After graduation, he spent two years in the

US Army The United States Army (USA) is the primary land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of the United Stat ...

at a physics research lab connected to the NSA, working as a cryptanalyst, which eventually sparked his interest in

quantum cryptography Quantum cryptography is the science of exploiting quantum mechanical properties to perform cryptographic tasks. The best known example of quantum cryptography is quantum key distribution, which offers an information-theoretically secure soluti ...

. From 1961 to 1963 he was a postdoctoral fellow at

UC Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a public land-grant research university in Berkeley, California, United States. Founded in 1868 and named after the Anglo-Irish philosopher George Berkele ...

in Geoffrey Chew's high-energy theory group. In 1964, he became a faculty member at the

. Greenberger soon became interested in gravity. Around 1970, he went to MIT to see Clifford Shull to test the

equivalence principle The equivalence principle is the hypothesis that the observed equivalence of gravitational and inertial mass is a consequence of nature. The weak form, known for centuries, relates to masses of any composition in free fall taking the same t ...

with neutrons from the university's reactor. As the reactor had been down for maintenance, Roberto Collela, Albert Overhauser, and Sam Werner devised a better way to do the experiment using a neutron interferometer. During a conference at

Grenoble Grenoble ( ; ; or ; or ) is the Prefectures in France, prefecture and List of communes in France with over 20,000 inhabitants, largest city of the Isère Departments of France, department in the Auvergne-Rhône-Alpes Regions of France, region ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

in 1978, Greenberger met with Michael Horne and Anton Zeilinger, which—by 1986—would eventually prove to be an important collaboration in the development of the Greenberger-Horne-Zeilinger state, a much improved version of

Bell's theorem Bell's theorem is a term encompassing a number of closely related results in physics, all of which determine that quantum mechanics is incompatible with local hidden-variable theories, given some basic assumptions about the nature of measuremen ...

quantum mechanics Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...

. In 1988, Greenberger won a Humboldt senior scientist award and went to

Munich Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...

in 1988 to work at the Max Planck Institute of Quantum Optics in Garching.

Work and current research

Together with Anton Zeilinger and Michael Horne, Greenberger wrote the first paper on

quantum entanglement Quantum entanglement is the phenomenon where the quantum state of each Subatomic particle, particle in a group cannot be described independently of the state of the others, even when the particles are separated by a large distance. The topic o ...

beyond two particles. The resulting GHZ theorem (see Greenberger-Horne-Zeilinger state) is fundamental for quantum physics, as it provides the most succinct contradiction between local realism and the predictions of quantum mechanics. Also, GHZ states were the first instances of multi-particle entanglement ever investigated. Such states have become essential in quantum information science. GHZ states are now even an individual entry in the PACS code.Going Beyond Bell's Theorem
24. 01. 2013. Currently Greenberger is still working on entangled states—especially with many particles. He continues to be an editorial board member and managing editor of the '' Fortschritte der Physik, International Journal of Quantum Physics'' and ''

Foundations of Physics ''Foundations of Physics'' is a monthly journal "devoted to the conceptual bases and fundamental theories of modern physics and cosmology, emphasizing the logical, methodological, and philosophical premises of modern physical theories and procedur ...

''.

References

{{DEFAULTSORT:Greenberger, Daniel 21st-century American physicists Fellows of the American Physical Society City College of New York faculty 1932 births Living people Massachusetts Institute of Technology alumni