QUANTUM TECHNOLOGY
Source: Hindu
Introduction:
Alain Aspect from the University of Paris-Saclay, John F. Clauser from California, and Anton Zeilinger are the laureates for the Nobel prize in physics. They have been awarded for experiments entangled photons, establishing the violation of Bell inequalities & pioneering quantum information science.
Reasons for the Award:
- The prize has been given for experimental work in quantum entanglement, which was referred to as 'Spooky action at a distance.
- John Clauser & Alain Aspect firmed up this concept, developing more complex experiments that demonstrated, and established that entanglement was indeed a true characteristic of quantum mechanics.
- Bell pairs were created, processed and measured.
- Anton Zeilinger innovatively used entanglement & Bell pairs, both in research & in applications.
- These include quantum computation & Quantum cryptography.
Quantum:
- Classical mechanics is the study of the dynamics of a system which uses Newton's laws of motion at the very basic level.
- The dynamics of a few bodies/particles interacting with each other can be described using classical mechanics.
- This can be extended to many particle systems, like a box containing millions of molecules of a gas, by employing the powerful technique of statistics, leading to statistical mechanics.
- A whole lot of activities can be encompassed by Newton's laws, classical mechanics and classical statistical mechanics.
- To understand the problems that could not be explained using classical mechanics, postulates of quantum mechanics were invoked.
Centre of Quantum Revolution:
- 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.
- For example, when a tennis ball is struck, it traces out a definite path in space. The path it traces out is called a Trajectory & it is possible to theoretically calculate the trajectory to any given accuracy.
- There is no restriction on measuring the speed/momentum of the ball at every point on the trajectory.
- Particles that fall into the quantum regime on the other hand-electrons or photons, do not possess a definite trajectory as they are not little hard spheres that were initially imagined them to be, but are weird wavelike quantum objects.
- Because of this, there is a limit to how precisely the position & momentum of the particles are measured simultaneously.
- One important difference in the behaviour of quantum systems, when compared to classical bodies is the concept of entanglement.
| Electronic devices use transistors that apply quantum mechanical ideas. Lasers have been built that apply the quantum properties of light. |
Quantum Entanglement:
- Quantum entanglement is a phenomenon by which a pair of particles like photons is allowed to exist in a shared state where they have complementary properties measuring the properties of one particle can lead to knowing the properties of other particles.
- For example, two coloured balls, one white & one black were packed in two boxes which look alike & no one knows which box contains which colour ball.
- One of the boxes is sent to Chennai, and the other is sent to Delhi.
- The person in Chennai who received the box can know not only the colour of the ball they have received but also that of the one in Delhi.
- This is a classical example & is somewhat trivial because nothing more can be made of it.
- If the ball obeys quantum mechanics, its colour is not known to the observer until it is observed.
- If the two balls occupy a shared state to start with, which is possible in quantum mechanics, however far the two may be transported, because of entanglement, opening one box can tell the user what the other ball is.
- Bell's inequalities are theoretical insights that make it possible to differentiate between two scenarios.
- One, that the indeterminacy of the colour of the balls is purely a quantum phenomenon, there are hidden variables that determine the colour when opened.
Practical Applications:
The work of the three laureates can help in developing quantum technologies. For instance, quantum cryptography and precise timekeeping as is done in atomic clocks.
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For Prelims: Quantum Technology Applications
Mains Question:
1. What is Quantum Entanglement? Discuss its applications
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