"This form of imaging uses pairs of photons, twins that are ‘entangled’ in such a way that the quantum state of one is inextricably linked to the other. While one photon has the potential to travel through the subject of a photo and then be lost, the other goes to a detector but nonetheless 'knows' about its twin’s life and can be used to build up an image." (http://www.nature.com/news/entangled-photons-make-a-picture-from-a-paradox-1.15781)
The counterintuitive predictions of quantum mechanics about strongly correlated systems were first discussed by Albert Einstein in 1935, in a joint paper with Boris Podolsky and Nathan Rosen. In this study, they formulated the EPR paradox (Einstein, Podolsky, Rosen paradox), a thought experiment that attempted to show that quantum mechanical theory was incomplete.
The EPR paper generated significant interest among physicists and inspired much discussion about the foundations of quantum mechanics (perhaps most famously Bohm's interpretation of quantum mechanics), but produced relatively little other published work. So, despite the interest, the flaw in EPR's argument was not discovered until 1964, when John Stewart Bell proved that one of their key assumptions, the principle of locality, was not consistent with the hidden variables interpretation of quantum theory that EPR purported to establish. (http://en.wikipedia.org/wiki/Bell%27s_theorem)
The work of Bell raised the possibility of using these super strong correlations as a resource for communication. ...
As an example of entanglement: a subatomic particle decays into an entangled pair of other particles. The decay events obey the various conservation laws, and as a result, the measurement outcomes of one daughter particle must be highly correlated with the measurement outcomes of the other daughter particle (so that the total momenta, angular momenta, energy, and so forth remains roughly the same before and after this process).
The seeming paradox here is that a measurement made on either of the particles apparently collapses the state of the entire entangled system—and does so instantaneously, before any information about the measurement could have reached the other particle (assuming that information cannot travel faster than light). In the quantum formalism, the result of a spin measurement on one of the particles is a collapse into a state in which each particle has a definite spin (either up or down) along the axis of measurement. ...
Recent studies shows that even time may be an emergent phenomenon that is a side effect of quantum entanglement.
When the new ideas of quantum mechanics spread through science like wildfire in the first half of the 20th century, one of the first things physicists did was to apply them to gravity and general relativity. And it immediately became clear that these two foundations of modern physics were entirely incompatible. When physicists attempted to meld the approaches, the resulting equations were bedeviled with infinities making it impossible to make sense of the results...
However in the mid-1960s the physicists John Wheeler and Bryce DeWitt successfully combined the previously incompatible ideas in a key result that has since become known as the Wheeler-DeWitt equation. The Wheeler–DeWitt equation is an attempt to combine mathematically the ideas of quantum mechanics and general relativity, a step toward a theory of quantum gravity. But in this approach, time plays no role in the equation, which introduced another significant "problem of time". In effect, it says that nothing ever happens in the universe, a prediction that is clearly at odds with the observational evidence. (http://en.wikipedia.org/wiki/Wheeler–DeWitt_equation)
In 1983 theorists Don Page and William Wootters suggested that quantum entanglement might provide a solution to the Wheeler-DeWitt "problem of time". When quantum objects are entangled, measuring the properties of one changes those of the other. Mathematically, they showed that a clock entangled with the rest of the universe would appear to tick when viewed by an observer within that universe. But if a hypothetical observer existed outside the universe, when they looked in, everything would appear stationary.(http://www.newscientist.com/article/dn24473-entangled-toy-universe-shows-time-may-be-an-illusion.html#.VH4frZD8JDs)
Recently, Ekaterina Moreva, Giorgio Brida, Marco Gramegna, Vittorio Giovannetti, Lorenzo Maccone, and Marco Genovese at the Istituto Nazionale di Ricerca Metrologica (INRIM) in Turin, Italy have performed the first experimental test of Page and Wootters’ ideas. And they confirm that time is indeed an emergent phenomenon for ‘internal’ observers but absent for external ones. (http://arxiv.org/abs/1310.4691)
Currently quantum entanglement has many applications in quantum information theory. With the aid of entanglement, otherwise impossible tasks may be achieved. Among the best-known applications of entanglement are superdense coding (http://en.wikipedia.org/wiki/Superdense_coding) and quantum teleportation (http://en.wikipedia.org/wiki/Quantum_teleportation).
Entanglement is also used in some protocols of quantum cryptography (quantum key distribution, etc). This is because the "shared noise" of entanglement makes for an excellent one-time pad. Moreover, since measurement of either member of an entangled pair destroys the entanglement they share, entanglement-based quantum cryptography allows the sender and receiver to more easily detect the presence of an interceptor (http://aeon.co/magazine/science/the-search-for-quantum-gravity/)
- Софийски УниверситетИнженерна физика – Микроелектроника и ИТ, 2014 - present
- Софийски УниверситетФизика, 2010 - 2014
- НПМГФизика, 2005 - 2010
- 81 СОУ „Виктор Юго“1998 - 2005
- Студент, present
Независима гражданска инициатива «За българска кирилица»
Независима гражданска инициатива «За българска кирилица»
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