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Daniel M. Greenberger (born 1932) is an American
quantum In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizati ...
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 caus ...
. He has been
professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who pr ...
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 within the City University of New York (CUNY) system in New York City. Founded in 1847, Cit ...
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 k ...
and—alongside
Anton Zeilinger Anton Zeilinger (; born 20 May 1945) is an Austrian quantum physicist and Nobel laureate in physics of 2022. Zeilinger is professor of physics emeritus at the University of Vienna and senior scientist at the Institute for Quantum Optics and Qu ...
—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, commonly called Bronx Science, is a public 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 involves passing the Spe ...
. He then graduated in 1954 from
MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...
, where he conducted his thesis under Laszlo Tisza. He received his MS (1956) and PhD (1958) from the
University of Illinois The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Universi ...
, where his advisor was Francis E. Low. After graduation, he spent two years in the
US Army The United States Army (USA) is the land warfare, land military branch, service branch of the United States Armed Forces. It is one of the eight Uniformed services of the United States, U.S. uniformed services, and is designated as the Army o ...
at a physics research lab connected to the
NSA The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collectio ...
, working as a
cryptanalyst Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic sec ...
, 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 solution ...
. 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. Established in 1868 as the University of California, it is the state's first land-grant univ ...
in Geoffrey Chew's high-energy theory group. In 1964, he became a faculty member 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 within the City University of New York (CUNY) system in New York City. Founded in 1847, Cit ...
. Greenberger soon became interested in gravity. Around 1970, he went to MIT to see Clifford Shull to test the
equivalence principle In the theory of general relativity, the equivalence principle is the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (s ...
with
neutrons The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave ...
from the university's reactor. As the reactor had been down for maintenance, Roberto Collela,
Albert Overhauser Albert W. Overhauser (August 17, 1925 – December 10, 2011) was an American physicist and a member of the National Academy of Sciences. He is best known for his theory of dynamic nuclear polarization known as the Overhauser Effect in nuclear m ...
, and Sam Werner devised a better way to do the experiment using a
neutron interferometer In physics, a neutron interferometer is an interferometer capable of diffracting neutrons, allowing the wave-like nature of neutrons, and other related phenomena, to be explored. Interferometry Interferometry inherently depends on the wave natu ...
. During a conference at
Grenoble lat, Gratianopolis , commune status = Prefecture and commune , image = Panorama grenoble.png , image size = , caption = From upper left: Panorama of the city, Grenoble’s cable cars, place Saint-A ...
in France in 1978, Greenberger met with Michael Horne and
Anton Zeilinger Anton Zeilinger (; born 20 May 1945) is an Austrian quantum physicist and Nobel laureate in physics of 2022. Zeilinger is professor of physics emeritus at the University of Vienna and senior scientist at the Institute for Quantum Optics and Qu ...
, 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 in
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, qu ...
. In 1988, Greenberger won a Humboldt senior scientist award and went to
Munich Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of the States of Germany, German state of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2020, it is the List of cities in Germany by popu ...
in 1988 to work at the
Max Planck Institute of Quantum Optics The Max-Planck-Institute of Quantum Optics (abbreviation: MPQ; german: Max-Planck-Institut für Quantenoptik) is a part of the Max Planck Society which operates 87 research facilities in Germany. The institute is located in Garching, Germany, ...
in
Garching Garching bei München (''Garching near Munich'') or Garching is a town in Bavaria, Germany, near Munich. It is the home of several research institutes and university departments on its campus. It became a city on 14 September 1990. Location The ...
.


Work and current research

Together with Anton Zeilinger and Michael Horne, Greenberger wrote the first paper on
quantum entanglement Quantum entanglement is the phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of ...
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 state Quantum entanglement is the phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of ...
s—especially with many particles. He continues to be an editorial board member and managing editor of the ''
Fortschritte der Physik The German Physical Society (German: , DPG) is the oldest organisation of physicists. The DPG's worldwide membership is cited as 60,547, as of 2019, making it the largest physics society in the world. It holds an annual conference () and multiple ...
, International Journal of Quantum Physics'' and '' Foundations of Physics''.


References

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