One of the boxes is sent to Vienna and the other to Madurai. Take two coloured balls, one black and one white, and put them in identical boxes so that no one other than you know which box contains the black ball. There is a trivial example of this from the classical domain. This is true however far apart the two particles are, provided the entanglement is not broken. Quantum entanglement is a phenomenon by which a pair of particles, say photons, is allowed to exist in a shared state where they have complementary properties, such that by measuring the properties of one particle, you automatically know the properties of the other particle. What is quantum entanglement? Does it have a classical counterpart? Harnessing what Einstein called spooky ‘action at a distance’ Lasers have been built that apply the quantum properties of light. What is the practical use of quantum mechanics?Įlectronic devices that we employ today use transistors that apply quantum mechanical ideas. One important difference in the behaviour of quantum systems, when compared to classical bodies, is the concept of entanglement, which is at the heart of this year’s Nobel Prize for physics. Many differences arise, starting from this fundamental difference. Because of this, there is a limit to how precisely you can measure the position and momentum of these particles simultaneously. Particles that fall into the quantum regime on the other hand - electrons or photons, for example - do not even possess a definite trajectory because they are not little hard spheres that we initially imagined them to be, but are weird, wavelike quantum objects. Simultaneously, there is no restriction on measuring the speed, or momentum of the ball at every point on the trajectory. The path it traces out is called a trajectory, and it is eminently possible to theoretically calculate the trajectory to any given accuracy. For example, when a tennis ball is struck, we see that it traces out a definite path in space. Many of the concepts that were useful in visualising the movement of particles in the classical realm break down when applied to particles obeying quantum mechanics. What is at the centre of the quantum revolution? Using ‘spooky action at a distance’ to link atomic clocks Some of the chief architects of this were Max Planck, Albert Einstein, Erwin Schrodinger, Werner Heisenberg and Niels Bohr. To understand these problems that could not be explained using classical mechanics, postulates of quantum mechanics were invoked. However, this approach breaks down when one wishes to describe subatomic particles such as light quanta. From describing a tennis match to sending a rocket to Mars this encompasses a whole lot of everyday activities. The success of Newton’s laws, classical mechanics, and classical statistical mechanics is not to be sneezed at. This can be extended to many particle systems, such as a box containing millions of molecules of a gas, by employing the powerful technique of statistics, leading to statistical mechanics. The dynamics of a few bodies or particles interacting with each other can be described using classical mechanics itself. Why is the word quantum so important here?Ĭlassical mechanics is the study of the dynamics of a system which uses Newton’s laws of motion at the very basic level. These include quantum computation and quantum cryptography. Anton Zeilinger innovatively used entanglement and Bell pairs, both in research and in applications. They did this by creating, processing and measuring what are called Bell pairs. John Clauser and Alain Aspect firmed up this concept, developing more and more complex experiments that demonstrated and established that entanglement was indeed a true characteristic of quantum mechanics. The prize has been given for experimental work in quantum entanglement, which Einstein referred to as ‘spooky action at a distance’. Why were these three physicists chosen for the award? They have been awarded “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science”, according to a press release given out by the Academy of Sciences, which is based in Stockholm, Sweden. and Anton Zeilinger, University of Vienna, Austria. They are Alain Aspect from the University of Paris-Saclay, France John F. The story so far: On October 4, the Nobel Committee of The Royal Swedish Academy of Sciences announced the names of three physicists as the laureates for the Nobel Prize in physics.
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