Quantum Communication

Context: At the first International Quantum Communications Conclave in New Delhi in March 2023, it was announced that India’s first quantum computing-based telecom network link is operational. 

  • The secure line is between Sanchar Bhawan and the National Informatics Centre at the Central Government Offices (CGO) complex in Delhi.

Quantum communication 

  • Quantum communication is an amalgamation of quantum mechanics and modern communication and Information Technology to study data transmission and processing. It takes advantage of the laws of quantum physics to protect data and securely transmit data.
  • Conventionally, 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), which makes it vulnerable to hackers who can read and copy it without a trace. Theoretically, this makes these networks ultrasecure. 
  • However, in a quantum communication network, data is transmitted via quantum bits or qubits. Qubits are particles, usually photons of light, in a superposition state, i.e., 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. 
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Data encryption 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).
    • QKD 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.


  • 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. 

UPSC Previous Year Question (2022)

Q. Which one of the following is the context in which the term “qubit” is mentioned?

(a) Cloud Services

(b) Quantum Computing

(c) Visible Light Communication Technologies

(d) Wireless Communication Technologies

Answer: (b) 

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