Recently, the Defence Research and Development Organisation (DRDO) of India successfully tested its Quantum Communication Technology developed ingeniously.

The Defence Research and Development Laboratory (DRDL) HQ and the Research Centre Imarat (RCI) both situated in Hyderabad communicated with each other as part of the test. The success of the test demonstrated the implementation Quantum Key Distribution (QKD) that makes the communication far more secure than classical information technologies. The technology heavily relies on quantum mechanics, especially on wave-particle duality. Let’s understand it.

Wave-Particle Duality says that every wave has a particle nature and every particle has a wave nature. When the particle becomes smaller and smaller, its wave nature becomes increasingly dominant. When the particle becomes so small that it starts to obey the laws of Quantum Mechanics, or becomes a quantum particle, its wave nature is described by the Schrodinger’s wave equation.

The Schrodinger Wave Equation gives the wave function for any quantum particle, i.e. it can describe any quantum particle in terms of its wave nature. The specialty of the quantum wave function is that it collapses to behave as a particle the moment it is attempted to be measured or detected thus giving only a tiny part of the total information it originally was carrying as a wave.

Let’s imagine that X wants to send an end to end encrypted message via a classical EM signal to Y. For that, X ciphers (encodes) the message with the help of a formula to decipher the message ( key). X, then secretly sends the key to Y so that Y can decipher the message and read the intended contents. If Z, acting as a spy, somehow intercepts the communication at any point between X and Y, then Z can use reverse engineering to trace the key and eventually shall be able to decipher the message without X or Y knowing that their communication has been hacked. This makes communication less secure despite the highest possible security standards using classical information technology.

However, in the case of Quantum Information Technology, the scenario is different. If X and Y use quantum communication, the encrypted signal is a quantum wave function which is only supposed to collapse at Y’s end after being sent by X. Thus it is designed to deliver the intended information to only Y. If Z tries to detect a part of the wave, thus making it to collapse at Z, the information delivered at Z won’t be the intended information that X wanted to send to Y. On top of it, the fact that a part of the quantum wave signal was intercepted midway will modify the unintercepted part of the signal generating a new key, called the Quantum Key that goes to both X and Y notifying both of them about the interception by Z. This advantage is based on Quantum Entanglement where any change to one of the particles entangled with another quantum mechanically, shall inadvertently modify the quantum state of the other.

In the entire process of Quantum Communication, there is one glaring problem. That is reducing the uncertainties at X and Y when the wave collapses or changes state. This is what Quantum Error Correction is all about.