Decoded: How quantum communication can become the future of data encryption

India's first quantum communication line is operational. Here's what this technology is

While speaking at the first International Quantum Communications Conclave in New Delhi on Monday, Union Minister for Communications, Electronics and Information Technology Ashwini Vaishnaw announced that India’s first quantum computing-based telecom network link now is operational.

The secure line is between Sanchar Bhawan and the National Informatics Centre at the Central Government Offices (CGO) complex in Delhi. The minister also challenged hackers to break the network’s encryption, offering a reward of Rs 10 lakh per break.

What is quantum communication?

Quantum communication is an amalgamation of quantum mechanics and modern communication and IT to study data transmission and processing. Also known as quantum information science and technology, it attempts to utilise the principles and concepts of quantum Mechanics to further technologies in telecommunications and IT.

What is a quantum communication network?

This communication network securely transmits data using the laws of quantum physics. Typically, sensitive data is encrypted and sent through fibre-optic cables with a digital “key” to decrypt the information. This data is transmitted in classical binary bits (0s and 1s), making it vulnerable to hackers who can read and copy it without a trace.

However, in a quantum communication network, data is transmitted via qubits. Qubits are particles – usually photons of light – in a superposition state, meaning they can be in multiple states and represent numerous combinations of 0 and 1. If a hacker tries to read this data, the qubits would “collapse” from their fragile quantum state to either a 0 or 1, thereby leaving a clear trace of external activity. Theoretically, this makes these networks ultra-secure.

How data encryption works in a quantum communication network?

Companies have recognised the additional security offered by quantum communication networks and have taken to transmitting sensitive data through a process called quantum key distribution (QKD).

This process involves the transmission of encrypted data as classical bits over networks while the decryption key is encoded and transmitted in a quantum state using qubits.

The most widely used scheme for this is the BB84, the world’s first quantum cryptography protocol. While there are several operational QKD networks in the world, China boasts the world’s longest one. Running a ground link of over 2,000 km between Beijing and Shanghai, banks and other financial institutions in China are already using this network to transmit data in an incredibly secure manner.

Are quantum communication networks really secure?

Theoretically, Quantum Communication networks are highly secure, with the built-in security of qubits and the simplified traceability of external interference in the signal.

However, these are predicated on the assumption that the machines used in the data encryption and transmission are secure and perfect, which may not be the case. The decay of the signal due to decoherence and the need for quantum repeaters for long-distance transmission is a systemic vulnerability that needs to be addressed. Quantum repeaters are nodes where the quantum keys are decrypted into bits and re-encrypted in a fresh quantum state to avoid signal loss.

A researcher from Georgia Institute of Technology reported in 2021 that a QKD network was hacked because the random number generator was not random at all. While this error was immediately patched, it exposes the extent to which these systems remain vulnerable despite the heightened security.