physics

Lev Vaidman

Lev Vaidman is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lev Vaidman rather than just read about it. In short: Lev Vaidman (Hebrew: לב ויידמן; born 4 September 1955) is a Russian-Israeli physicist and professor at Tel Aviv University, Israel. He is noted for his theoretical work in the area of fundamentals of quantum mechanics, which includes quantum teleportation, the Elitzur–Vaidman bomb tester, and the weak values.

Key takeaways

Lev Vaidman belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lev Vaidman to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lev Vaidman from memory before moving on to harder problems.

Reference excerpt

Lev Vaidman (Hebrew: לב ויידמן; born 4 September 1955) is a Russian-Israeli physicist and professor at Tel Aviv University, Israel. He is noted for his theoretical work in the area of fundamentals of quantum mechanics, which includes quantum teleportation, the Elitzur–Vaidman bomb tester, and the weak values. He was a member of the Editorial Advisory Board of The American Journal of Physics 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 in Saint Petersburg and was twice among the winners of the All-Soviet high school students Physics Olympiad (first place in 1971 and second place in 1972), and in 1972 scored 26th in the International Physics Olympiad in Bucharest. 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 (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 paradoxical. 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 to 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 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 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 of quantum mechanics.

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.

See also Avshalom Elitzur Elitzur–Vaidman bomb tester Englert–Greenberger duality relation Interaction-free measurement Many-worlds interpretation

References

External links Lev Vaidman's homepage Publications list 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-print arXiv:hep-th/9305062, submitted 14 May 1993

Illustrations

Worked examples

Example 1 — a first encounter with Lev Vaidman

Start with the simplest possible case. Write down what Lev Vaidman claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lev Vaidman before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lev Vaidman ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lev Vaidman

In research: Lev Vaidman appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lev Vaidman in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lev Vaidman is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1955 births, Academic staff of Tel Aviv University, Israeli Jews, so understanding it makes those chapters shorter.
In everyday life: Look for Lev Vaidman outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lev Vaidman in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lev Vaidman means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lev Vaidman out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lev Vaidman in simple terms?

Why does Lev Vaidman matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lev Vaidman?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lev Vaidman.