Lev Vaidman (born 4 September 1955) is a Russian-Israeli

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 ...

and Professor at

Tel Aviv University Tel Aviv University (TAU) ( he, אוּנִיבֶרְסִיטַת תֵּל אָבִיב, ''Universitat Tel Aviv'') is a public research university in Tel Aviv, Israel. With over 30,000 students, it is the largest university in the country. Locate ...

, Israel. He is noted for his theoretical work in the area of fundamentals of

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, ...

, which includes quantum teleportation, the Elitzur–Vaidman bomb tester, and the

weak value In quantum mechanics (and computation), a weak value is a quantity related to a shift of a measuring device's pointer when usually there is pre- and postselection. It should not be confused with a weak measurement, which is often defined in conjunc ...

s. He was a member of the Editorial Advisory Board of ''The

American Journal of Physics The ''American Journal of Physics'' is a monthly, peer-reviewed scientific journal published by the American Association of Physics Teachers and the American Institute of Physics. The editor-in-chief is Beth Parks of Colgate University."Current Fre ...

'' from 2007 to 2009. In 2010, the Elitzur–Vaidman bomb tester was chosen as one of the "Seven Wonders of the Quantum World" by New Scientist Magazine.

Personal life

He attended

45th Physics-Mathematics School Dmitry Konstantinovich Faddeev Academic Gymnasium at Saint Petersburg State University (russian: Академическая гимназия имени Д. К. Фаддеева Санкт-Петербургского государственного ...

Saint Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...

and was twice among the winners of the All-Soviet high school students

Physics Olympiad The International Physics Olympiad (IPhO) is an annual physics competition for high school students. It is one of the International Science Olympiads. The first IPhO was held in Warsaw, Poland in 1967. Each national delegation is made up of at ...

(first place in 1971 and second place in 1972), and in 1972 scored 4th in the International Physics Olympiad in

Bucharest Bucharest ( , ; ro, București ) is the capital and largest city of Romania, as well as its cultural, industrial, and financial centre. It is located in the southeast of the country, on the banks of the Dâmbovița River, less than north of ...

. Vaidman emigrated with his family to Israel at the age of 18. Prior to that, he studied for one year at Saint Petersburg University (then Leningrad University).

The Elitzur–Vaidman bomb tester

This thought experiment, subsequently conducted in the lab, is an example of

interaction-free measurement In physics, interaction-free measurement is a type of measurement in quantum mechanics that detects the position, presence, or state of an object without an interaction occurring between it and the measuring device. Examples include the Renninger ne ...

(IFM). IFM is the detection of the property of an object or its presence without any physical interaction between the observer and the object. Obtaining information from an object in such a manner is

paradox A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically u ...

ical. The bomb tester works by employing an interferometer. When a photon is fired into the device, it encounters a half-silvered mirror positioned so as reflect the photon at a ninety-degree angle. There is a 50-50 chance it will be reflected or pass through. Due to the

quantum properties 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 ...

of the photon, it both passes through the mirror and is reflected off of it. Now, the same photon is moving through two different parts of the device. The photon that passed through the mirror is now on the "lower path". It may or may not encounter a bomb, which is designed to explode if it encounters a single photon. The photon that was reflected off the mirror is now on the "upper path". Both photons next encounter a normal mirror. The ''lower-path'' photon is reflected ninety-degrees upward (if it did not detect a bomb). The ''upper-path'' photon is reflected back ninety degrees so that it is returned to its original trajectory. If the ''lower-path'' photon did not detect a bomb, it will arrive at a second half-silvered mirror at the same time as the ''upper-path'' photon. This will result in the single photon

interfering Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extr ...

with itself. A pair of detectors are positioned beyond the mirror in such a way that the photon's superposition collapses and the photon is observed to have either been on the upper path or the lower path, but not both. If the ''upper-path'' detector encounters the photon, then the photon "actually" took the upper path and no measurement was made of whether or not there was a bomb on the lower path. If, however, the ''lower-path'' detector encounters a photon, it can be determined that fifty percent of the time, there is a bomb on the lower path--''without actually encountering it''. Vaidman has argued that this lends support to the

many-worlds interpretation The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wave function collapse. This implies that all possible outcomes of quantum me ...

Teleportation of continuous variables

Vaidman is a pioneer in the area of quantum teleportation. He has demonstrated that non-local measurements can be used to teleport unknown quantum states of systems with continuous variables.Zhang, L., Barhen, J., Liu H.
''Experimental and Theoretical Aspects of Quantum Teleporation''
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References

External links

Lev Vaidman's homepage

The Stanford Online Encyclopedia of Philosophy entry on the Many-Worlds Interpretation of Quantum Mechanics, by Lev Vaidman
* Lev Vaidman, ''Teleportation of Quantum States'', Phys. Rev. A 49, 1473-1476 (1994). Pre-prin
arXiv:hep-th/9305062
submitted 14 May 1993 {{DEFAULTSORT:Vaidman, Lev 1955 births Living people Israeli physicists Tel Aviv University faculty Soviet emigrants to Israel Israeli Jews Soviet Jews Scientists from Saint Petersburg Quantum physicists Jewish physicists

Personal life

The Elitzur–Vaidman bomb tester

Teleportation of continuous variables

See also

References

External links