Quantum Key Distribution (QKD) and the role of optical circuit switching in secure networking.

Written by 

Rohit Kunjappa

Head of Product Management & Application Engineering 

In an increasingly interconnected world, data security has become paramount. Traditional encryption methods, while robust, face threats from ever-evolving quantum computing capabilities. This is where Quantum Key Distribution (QKD) comes into play. QKD is a cutting-edge technology that leverages the principles of quantum mechanics to secure communication channels. In this blog, we will provide an overview of QKD and explore how optical circuit switching can enable the deployment of secure QKD networks.

Understanding Quantum Key Distribution (QKD)

QKD is a cryptographic technique that harnesses the fundamental principles of quantum mechanics to create secure communication channels. It relies on the properties of quantum entanglement and the Heisenberg Uncertainty Principle to generate encryption keys that are practically unbreakable. Here is a breakdown of how QKD works:

1.    Quantum key generation: QKD systems use a source of quantum particles, typically photons, to transmit information. These particles are encoded with quantum states, such as polarizations, that represent 0’s and 1’s in binary code.

2.    Transmission: The quantum particles are then sent over a communication channel to the recipient. Any attempt to eavesdrop on the transmission will inevitably disturb the quantum states, alerting both parties to the intrusion.

3.    Key comparison: The sender and receiver compare a subset of the quantum states they received to check for any discrepancies caused by potential eavesdropping. If the channel is secure, they proceed to distill a shared secret key.

4.    Secure communication: With the shared secret key in hand, the sender and receiver can use it for secure communication, such as encrypting and decrypting data.

QKD offers the promise of "future-proof" security, as even the most advanced quantum computers would struggle to crack the encryption generated through this method between key updates. One important factor to consider here is that the cryptographic keys communicated through the quantum channels should be updated as frequently as possible. The rate at which this can be performed is dependent on the capabilities of the QKD transmitters (often referred to as “Alices”) and receivers (“Bobs”) and the quality of the optical fiber links between them. 

However, deploying QKD at scale in a network requires careful consideration of the underlying infrastructure.

The role of optical circuit switching

To realize the full potential of QKD for secure networking, we need a robust and flexible network infrastructure. Optical circuit switching (OCS) can play a vital role in this context. OCS is a technology that enables the dynamic allocation of optical resources, allowing for efficient and secure data transmission. 

Here's how OCS can enhance QKD networking:

1.    Resource allocation: OCS allows for on-the-fly allocation of dedicated optical circuits for QKD communication. This ensures that quantum keys are transmitted over a secure, interference-free channel, minimizing the risk of eavesdropping.

2.    Low latency: OCS offers low-latency switching, which is crucial for QKD. The speed at which quantum keys are exchanged and verified is critical for maintaining secure communication.

3.    Scalability: As QKD networks grow, OCS can adapt to the changing demands by reallocating optical circuits as needed. This scalability ensures that QKD can be seamlessly integrated into existing and future network architectures.

4.    Diverse applications: Beyond QKD, OCS can also support other secure communication technologies, such as traditional encryption methods and data center interconnects, making it a versatile tool for network security.


Quantum Key Distribution holds immense promise for securing communications in the age of quantum computing. However, to fully leverage the potential of QKD, a robust network infrastructure is essential. Optical circuit switching provides the flexibility, speed and security required to enable a seamless QKD network. 

See our related blog on OCS for Quantum Networking

Learn more about POLATIS optical circuit switches and how the technology would benefit your applications here: