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5 Most Significant Challenges Facing Quantum Cryptography

5 Most Significant Challenges Facing Quantum Cryptography
There are several challenges facing quantum cryptography – but the payoff will be worth it


Quantum cryptography is still in its infancy in terms of practical application. The drawn-out implementation of quantum cryptography is a result of challenges regarding transmission rates and processing limitations. Currently, these issues are complicated to overcome as the need for high-quality single photons from a laser over long distances requires low transmission loss rates, which means lower signal-to-noise ratios for the channel. As a result, the equipment cost of this technology is much higher than that of traditional cryptography. Additionally, processing limitations exist due to the need to perform quantum state manipulation at the receiver’s site to ensure adequate security and data protection.


Challenge #1: Maintaining A Quantum Communication Network

The cost of creating and maintaining a quantum communication network is a significant factor that needs to be addressed. Using existing legacy communication infrastructure is a less expensive approach. However, this isn’t an option for quantum cryptography as the data rate for existing infrastructure is much lower than the Nyquist rate, limiting the maximum number of photons per second that can be sent.

The best way to overcome this limitation is to use quantum states capable of traveling over longer distances, which requires a new high-grade single-photon source and the adoption and development of more cost-effective networks.


Challenge #2: Transferring Quantum States

Another significant challenge that faces quantum cryptography and quantum computing is an effective method to transfer quantum states from one place to another via a single photon channel at rates greater than 1 Gbit/s (1 Terabit per second).

The most common type of light source used to create a single photon is the Alexandrite laser. The primary limitation of this light source is that it produces light of relatively low intensity and has a relatively low quantum yield. However, ionization methods have a high enough quantum yield to produce the required data rates. They do not depend on the physical properties of the laser, so they are, in principle, unlimited.

A scheme that uses long-distance single-photon propagation and the conversion of an ionized exciton into an optical superposition state is also being developed as a solution.


Challenge #3: A Means For Secure Encryption

The third challenge facing the implementation of quantum cryptography is the need to understand better how to utilize this emerging technology to meet all data security protection requirements.

Industry leaders must create realistic models that take advantage of quantum cryptographic technologies and can be implemented effectively.

We regularly see the development of novel protocols that aim to outperform established protocols. While this is encouraged for the development of the technology, it does introduce additional complexity. With technical constraints applied, these protocols begin to exhibit several advantages. And as testing continues, we will start to see an increase in the alignment across protocols and the practical application thereof.


Challenge #4: Public Trust

A hurdle that all new technologies must overcome eventually is public adoption. The widespread implementation and use of quantum key distribution systems and other quantum protocols still face issues with trust, particularly from the public sector. Potential users and clients need assurance from government agencies that data encryption will be secure within the machines on which this new form of PKI (public key infrastructure) will reside.


Challenge #5: Sharing Infrastructure

The final challenge in quantum cryptography is the need for shared infrastructure required for the communication between several applications. Quantum cryptographic standards, such as post-quantum cryptography and quantum-public key cryptosystems, utilize public-key encryption as part of a larger data security model in which multiple machines can securely share both encryption and decryption keys. This approach makes it easier for users and businesses alike to develop their security with quantum cryptographic properties.

Setting the topology that allows for multiple users to access the network is challenging. The popular star topology is suitable for relatively short distance transfers (up to 400km); as a result, more networks and devices are required to cover a greater distance. An effective solution for increasing the range of communication would be introducing an intermediate node between any two users. This could allow for secure quantum communication among all users without requiring a trusted relay. Thus reducing the cost per user since only one set of measurement devices is necessary for a large shared network.



There are several challenges facing quantum cryptography that range from infrastructure development to public adoption and global-scale networks. Addressing these challenges is complex, and many of the world’s brightest individuals are working hard to come up with the necessary solutions. Thankfully the pay-off is well worth the effort, and the reward of a more secure future is one that we proudly strive for.