Quantum key distribution (QKD) is a method of secure communication that uses principles of quantum mechanics to establish a secure key between two parties. The key can then be used for encrypting and decrypting messages, ensuring that the communication between the parties is secure and cannot be intercepted by eavesdroppers. In QKD, the key is generated using quantum properties such as the superposition and entanglement of quantum particles. These properties ensure that any attempt to intercept or measure the key will disturb the quantum state, alerting the parties to the presence of an eavesdropper. QKD offers a high level of security compared to classical encryption methods, as it is based on the fundamental laws of physics and is resistant to hacking attempts using classical computing power. It is considered to be a key technology for achieving secure communication in the age of quantum computing and increasing cyber threats.

Continuous variable quantum key distribution (CV-QKD) is a type of quantum key distribution protocol that uses continuous variables, such as the quadrature amplitudes of light, to encode and transmit quantum information. In CV-QKD, the quantum states are typically represented by continuous variables rather than discrete quantum states like qubits. CV-QKD offers several advantages over discrete-variable QKD protocols, such as higher key rates and simpler implementation using existing optical communication technologies. It is particularly well-suited for long-distance communication and can achieve high secret key rates over fiber-optic networks. In CV-QKD, the quantum information is encoded in the continuous variables of the light field, such as the amplitude and phase of the electromagnetic waves. The key distribution process involves measuring these continuous variables at the sender and receiver’s ends to establish a secure key that can be used for encryption and decryption.

Parsa QKD is the first Iranian fiber-based CV-QKD system that employs Gaussian-modulated coherent state (GMCS) of laser light to ensure secure communication between two nodes.