# Daniel M Greenberger

Marshak Science Bld, Rm 314

160 Convent Ave

New York , NY 10031

### Education:

- B.S., M.I.T.
- M.S., Univ. of Illinois, Ph.D.

### Biography:

I went to the Bronx High School of Science, where I graduated in 1950, in a class that included the two Nobel Prize winners Steven Weinberg and Sheldon Glashow. The same class included the APS Buckley Prize winner and former president of the APS, Myriam Sarachik, as well as other well known physicists Gary Feinberg and Morton Sternheimer. It was a good year for physicists.

I went to MIT as an undergraduate, and wrote my thesis under Prof. Laszlo Tisza, graduating in 1954. I went to graduate school at the Univ. of Illinois, getting a Masters degree in 1956, and my Ph. D. in 1858. However, after I passed my qualifying exams in 1956, my thesis advisor, Prof. Francis Low, moved on to MIT, so I followed him there and spent two years writing my Ph. D. thesis at MIT, although my degree comes from Illinois.

When I graduated, I had to spend two years in the US Army, to fulfill an ROTC obligation, since they were nice enough to let me finish graduate school first. I served most of my time at a physics research lab., officially connected to the NSA, outside of Washington, DC, next to the U. of Maryland campus, and got to know the Maryland faculty. (The Army trained me as a cryptanalyst, which I never dreamed could be useful in my career. But one of the subjects I am interested in today is quantum cryptography, so you never know.)

Then I went to Ohio State University for one year, and won an NSF post-doc. fellowship, and went to Berkeley to work in Geoffrey Chew's group, from 1961 to 1963. All this time I was a high-energy theorist. I was hired by CCNY in Sept. 1964, and have been there ever since.

But I soon changed fields, becoming interested in gravity, and thought up an experiment to test the equivalence principle with neutrons. I went to see Prof. Cliff Shull at MIT around 1970 to see if he could do the experiment. He thought so, but the MIT reactor was down for two years. In the meantime, Roberto Collela, Al Overhauser, and Sam Werner, thought of a better way to do the experiment and did it beautifully, using the neutron interferometer, which was new at that time. I then started a collaboration with Al Overhauser, and we have been good friends ever since. In 1978, I went to a conference at Grenoble in France, where they had the world's biggest nuclear reactor, and met Cliff Shull again, and Mike Horne, and Anton Zeilinger there. They were all collaborating at MIT, and I started to go up there visiting them regularly, and becoming part of their group, and we have been collaborating for 30 years. In 1980, I spent a year at MIT on sabbatical.

This kept up until the middle 80's when Prof. Shull retired, and MIT stopped doing neutron diffraction. Prof. Shull won the Nobel Prize shortly after he retired. Anton Zeilinger moved on to the Atominstitut at the T.U. in Vienna when Prof. Shull retired, and I went to visit him there on sabbatical with a Fulbright grant in 1986. There we discovered the GHZ (Greenberger-Horne-Zeilinger) theorem, a much improved version of Bell's theorem in quantum mechanics, although we did not publish it until 1989. Prof. Zeilinger moved on to Innsbruck, and started a quantum optics lab. I won a Humboldt senior scientist award and went to Munich in 1988, to work with Prof. H. Walther at the Max Planck Inst. in Garching.

### Current Research:

Since this time I have been working on fundamental problems in quantum theory, mostly using quantum optics. Prof. Zeilinger started a quantum Optics lab. at the Univ. of Vienna around 1990, and I have been visiting there regularly and collaborating with his group. Some other high points have been that a two issue festschrift was published for me by the Journal Foundations of Physics on my 65th birthday, I was elected a fellow of the APS, the Nobel Prize Committee in physics hired me as a consultant, and Prof.Zeilinger and I founded the topical group on Quantum Information for the APS, which at last count had well over 600 members. I have also organized a number of meetings on quantum mechanics, including two large ones, one of which honored Eugene Wigner, and the other honored John Wheeler. I am also on the editorial boards of a number of journals, and am still doing research on entangled states in quantum mechanics.

I am currently still working on entangled states, as I believe that these states afford a deep insight into the working of quantum mechanics. I am especially doing research into entangled states with many particles, as I believe these will prove to have relevance to biology and chemistry.

I also believe entangled states can be used to shed light on some deep questions involving the nature of time in relativity theory. I am looking at the possibility of coordinating spacelike systems, and its implications, even though they cannot communicate directly with each other.

I am also engaging in a very speculative project, which involves time-travel in quantum theory. There is also much work on this area in general relativity, but I believe that quantum theory itself is a natural place in which to look for such behavior, as already one can see such phenomena as quantum teleportation.

### Publications:

"Time Travel in Quantum Theory", with K. Svozil, article in *Quo Vadis Quantum Mechanics*, A. Elitzur, S. Dolev, and N. Kolenda, eds., Springer, Berlin, 2005. Placed on the Quant. Ph. ArXiv., no. 0506027, June 2005.

"The Tic-Tac-Toe Theory of Gravity", article in* Proceedings of the 6th Workshop on Mysteries, Puzzles, and Paradoxes in Quantum Mechanics, Gargnano,* R. Bonifacio, B. G. Englert, and S. Severio, eds., (in press).

“Adventures in s-waves”, with J. P. Dahl,* et al,* Fortsch. der Phys., (in press).

“A General GHZ-type Theorem for Two Particles, Using 100% Efficient Counters”, with M. A. Horne, and A. Zeilinger, Quant-ph. ArXiv: 05010201, v. 2, (Phys. Rev. A, in press).

“A General GHZ-type Theorem for Two Particles, Using Inefficient Counters”, with M. A. Horne, and A. Zeilinger, Quant-ph. ArXiv: 05010207, v. 2, (Physs. Rev. A, in press).

"Planck, Quantum Fluctuations, and Bose-Einstein Condensation", with M. Scully, *et al*., article in *Progress in Optics, Vol 50*, E. Wolf., ed., Elsevier, 2007.

Co-editor of "Compendium of Quantum Mechanics", an encyclopedia for philosophers of science and scientists, Springer, expected publ. date, 2009.

### Invited lectures:

The Perimeter Institute, Waterloo, Canada,

Workshop on Quantum Information, U. of Vienna,

The Technical University of Vienna,

the Rochester Conference, Rochester,

Workshop on quantum theory, Princeton U.,

Cambridge University (England),

Imperial College, London,

Temple University,

Lehigh University,

U. of Missouri at St. Louis,

U. of Maryland,

U. of Texas at Austin,

Texas A. & M. Univ.,

Amherst College

National Univ. of Singapore,

Conference on Philosophy and Quantum Theory, New Delhi.

### Editorial Board Member:

Foundations of Physics Letters,

*Fortschritte der Physik,

*Int'l Journal of Quantum Information, (Managing editor).

*Foundations of Physics

(*= currently on the board)

Started (with A. Zeilinger) and served as initial organizer in 2005 of the Quantum Information Topical Group of the American Physical Society (currently over 600 members).