Social media was abuzz upon the news of successful testing of quantum key distribution in India. While it is beyond a layman’s understanding, congratulations were poured in for DRDO IIT-Delhi for this unique achievement.
In a first for the nation, the successful demonstration of quantum key distribution was witnessed between Prayagraj and Vindhyachal in Uttar Pradesh, two places located 100 kilometres apart. This success has demonstrated the country’s indigenous technology of secure key transfer for bootstrapping military-grade communication security key hierarchy. The technology helps security agencies plan for a suitable quantum communication network using an indigenous technology backbone.
So, what is quantum key distribution?
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Quantum key distribution (QKD) is the use of laser beams to transmit cryptographic keys securely using photons. These photons are coded in binary ones and zeroes and are later picked by the receiving equipment. This makes it possible to transmit keys without getting intercepted.
The concept of quantum key distribution was first proposed in the 1970s by Stephen Wiesner from Columbia University in New York, but it was only in the 1980s that it saw some development. Although the idea was simple, it was in the 1990s when Artur Ekert, a PhD student at Wolfson College, University of Oxford, developed a different approach to quantum key distribution based on quantum entanglement. The most mature quantum technology has been commercially available for over 15 years now.
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There are currently six companies offering commercial quantum key distribution systems around the world; ID Quantique (Geneva), MagiQ Technologies, Inc. (New York), QNu Labs (Bengaluru), QuintessenceLabs (Australia), QRate (Russia) and SeQureNet (Paris). Several other companies like Toshiba, HP, IBM, Mitsubishi, NEC and NTT have active research programmes.
There are two main categories of quantum key distribution.
Prepare and Measure Protocols: This focuses on measuring unknown quantum states and can be used to detect eavesdropping (spying) and measure how much data was potentially intercepted.
Entanglement-based Protocols: This focuses on quantum states where two objects are linked to form a combined quantum state. In this method, if there is an interception and if an eavesdropper gets access to a previously trusted node and changes something, the other involved parties will be alerted about it.
How does quantum key distribution work?
- Encryption keys are sent in the form of ‘qubits’ (quantum bits are the equivalent of bits in a binary system) in an optical fibre. These optical fibre networks can transmit more data to longer distances and faster than other media.
- Implementing quantum key distribution requires interactions between legitimate users. These interactions need to be authenticated and achieved through various cryptographic means. Quantum key distribution allows two distant users to produce a common, random string of secret bits known as the secret key.
- Quantum key distribution can utilise an authenticated communication channel and transform it into a secure one. QKD is designed in a manner that if there is any illegitimate entity that tries to read the transmission, it will disturb the qubits that are encoded on photons. This interception will generate transmission errors, immediately informing legitimate end-users.
What are the challenges associated with quantum key distribution?
- Integration of QKD systems into current infrastructure—it is currently challenging to implement an ideal infrastructure for QKD; although it sounds secure in theory, in practice, imperfect tools like single-photon detectors can create many security vulnerabilities.
- In modern fibre optic cables, a limited distance in which photons can travel can typically carry a photon to a maximum of only 100 km.
Way forward for quantum key distribution
Many startups and big tech corporations are developing quantum technology and applications, and these efforts must be harnessed. India’s Union Budget of 2020-21 saw the allocation of Rs 8,000 crore towards the National Mission on Quantum Technologies and Applications. Since 2019, India has come a long way in quantum technology, and more can be done to bring all the efforts together.