The Quantum Revolution
Journey of Quantum Mechanics to Quantum Computing in short
First Quantum Revolution
In the early 1900s, scientists started realizing that their understanding of the universe was not consistent at small scales. In the late 1800s physicists were able to explain the things we see around us in the world.
They were able to explain the behavior of light e.g. Transmission, Reflection, Refraction, Diffraction etc.
They were also able to explain the motion of objects e.g. the motion of a pendulum.
They were able to explain the movements of stars and planets.
However, in the 1900s, scientists discovered that small objects didn't obey classical laws of physics. There were many experiments done by Max Planck, Niel's Bohr etc that lead to the idea that nature is quantized.
Neil Bohr proposed the atomic model based on the fact that Quantum Mechanical things have different energy levels.
Max Planck introduced the idea of quantized behavior which gives birth to quantum mechanics.
Einstein proposed a photoelectric effect leading to dual nature.
In the classical world, any object thrown against a wall bounces back. But in the Quantum world, the object can also pass through the wall with some probability.
If you leave a classical object in some position and if you go away then after some time you will see the object in the same position. But if a quantum object is placed at some position at some time 't1' then it won't be at the same position at some other time 't2'. This is because when we leave the object at time 't1' we know its exact position. But in the quantum world, we can't know all the properties of the object at once. So if we know the position, we can't know the velocity. This is Heisenberg's uncertainty principle.
In the classical world, if you throw an object toward a goal, you can watch it move toward the goal. But in the quantum world when we throw an object towards a goal it just floats or just stops at some place in the air. When we blink an eye it moves a little i.e. the quantum object will only move when we're not looking at it. Looking at the object is the same as measuring the object. This is called as Quantum Zeno Effect.
Thus the first quantum revolution was discovery of quantum mechanics and its properties.
Second Quantum Revolution
It is the recent quantum revolution which involves using quantum mechanics and leveraging its properties, controlling individual quantum systems in turn developing powerful new technologies. E.g. Quantum Internet, Quantum computer, Quantum control of molecules.
The Second Quantum Revolution includes Quantum Information Science and Engineering(QISE), which studies many different uses of Quantum Mechanics. Quantum Computing, Quantum Sensing, Quantum Networking are subsets of QISE.
Quantum Computing is doing computation using laws of quantum physics and involves leveraging the quantum mechanical properties. Quantum sensing gives more powerful sensors than the classical sensors. Quantum Networking involves distributing Quantum Information. There are various other subfields like Quantum Music, Quantum Machine Learning, Quantum Finance etc. Quantum computing can be used in vaccine development, combating climate change, simulation of chemical molecules, cyber security etc.