Explanation:

? Recent Context: For the first time in the country, the Indian Space Research Organisation (ISRO) has successfully demonstrated free-space Quantum Communication over a distance of 300 m.
? A number of key technologies were developed indigenously to accomplish this major feat, which included the use of indigenously developed NAVIC receiver for time synchronization between the transmitter and receiver modules, and gimbal mechanism systems instead of bulky large-aperture telescopes for optical alignment.
? The demonstration has included live video conferencing using quantum-key-encrypted signals. This is a major milestone achievement for unconditionally secured satellite data communication using quantum technologies.
? The Quantum Key Distribution (QKD) technology underpins Quantum Communication technology that ensures unconditional data security by virtue of the principles of quantum mechanics, which is not possible with conventional
encryption systems. The conventional cryptosystems used for data encryption rely on the complexity of mathematical algorithms, whereas the security offered by quantum communication is based on the laws of Physics. Therefore, quantum cryptography is considered ‘future-proof’, since no future advancements in computational power can break the quantum cryptosystem. Hence statement 1 is not correct.
? The free-space QKD was demonstrated at Space Applications Centre (SAC), Ahmedabad, between two line-of-sight buildings within the campus. The experiment was performed at night, in order to ensure that there is no interference from the direct sunlight. The experiment is a major breakthrough towards ISRO’s goal of demonstrating Satellite-Based Quantum Communication (SBQC), where ISRO is gearing up to demonstrate the technology between two Indian ground stations. The communicating objects need not necessarily be in each other's line-of-sight. Hence statement 2 is not correct. The longest QKD network is in China of around a 2000-kilometer ground link between Beijing and Shanghai.
? Quantum communication takes advantage of the laws of quantum physics to protect data. These laws allow particles—typically photons of light for transmitting data along optical cables—to take on a state of superposition, which means they can represent multiple combinations of 1 and 0 simultaneously. The particles are known as quantum bits, or qubits. The significance of qubits from a cybersecurity perspective is that if a hacker tries to observe them in transit, their super-fragile quantum state “collapses” to either 1 or 0. This means a hacker can’t tamper with the qubits without leaving behind a telltale sign of the activity. It enables two communicating users to detect the presence of any third party trying to break into the communication network. Hence statement 3 is correct.