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Quantum communication


Quantum computing technologies will continue to develop and improve in 2024. One of the main aims of the field has been to improve the accuracy of quantum computation so that calculations are performed with fewer errors. Another fast-growing area is quantum communication, used to increase the security of data encryption across new quantum networks.


To send quantum data over long distances, photons are used as qubits (quantum bits, analogous to classical bits used in classical computing). Photons are transmitted over fibre optic cables that are laid underground, above-ground or under the sea. The advantage of using photons for quantum communication is that fibre optic cable networks already exist across the globe and are used, for example, to receive and transmit data over the internet.

Data encryption

When sending data over the internet, such as in online financial transactions or when sending an email, data encryption is used to securely transmit the data without allowing a third party to read it. To encrypt data sent over the internet, complicated mathematical algorithms are used. If a third party wanted to access this secure data, these algorithms would have to be solved by a computer. Classical computers could take months or even years to break these algorithms[1], ensuring the safety of the encrypted data. However, quantum computing is capable of solving these algorithms on much shorter timescales.


The potential threat posed to current data encryption methods by advancements in quantum computing, is driving developments in quantum cryptography. Quantum cryptography aims to provide more secure data encryption protocols against potential quantum hacking for data transmission across quantum networks.


Patents in the field of quantum cryptography are directed both toward hardware and software. For example, EP1748595 describes apparatus that enables the communication of quantum encrypted data, whereas EP3758289 describes both an algorithm that can withstand quantum attacks as well as suitable hardware for the implementation of the algorithm.


Data transmission

In quantum communication, data is transmitted using qubits instead of classical bits. The advantage of transmitting qubits is that an eavesdropper can be easily detected. This is primarily because if an eavesdropper attempted to read the quantum data, the quantum state of the qubit would collapse (a simplified explanation of this can be found in Part II of this series). Additionally, the data cannot be copied by a third party. This is due to the no-cloning theorem of quantum mechanics, which essentially says that it is impossible to create an identical copy of an unknown quantum state.


As well as a more secure means of data transfer, quantum communication also allows a near-instantaneous transmission of data. Quantum communication networks are therefore being actively researched and built by various companies and government institutions. These networks can be built using two forms: (i) on-the-ground cable communication; and (ii) satellite communication. The main limitation in either of these communication forms is the loss of photons with distance. Photons can be lost due to scattering or absorption, and increasing the distance of travel also increases the probability of photon loss.


Quantum networks

One of the organisations actively developing quantum communication networks is the Quantum Corridor TM. This organisation is developing one of the fastest fiber-optic quantum networks in North America, stretching between Indiana and Chicago. Their aim is to provide businesses, research centres and government facilities with the ability to transmit data at nearly instantaneous speeds. In November 2023, data sent over the current 19 km network was sent with a delay of only 0.266 milliseconds[2]. Companies such as Toshiba Systems, that have already developed methods for transmitting encrypted quantum data over fiber-optic cables (e.g. EP3220574), are also using this network to apply their technologies[3].


Another quantum communication network is being developed between England and Ireland[4], using the recently built subsea fibre optic network Rockabill[5] that stretches over 224 km. Experiments in 2023 conducted by researchers from the University of York in collaboration with the Quantum Communications Hub and euNetworks Group Limited (who funded the construction of Rockabill), showed that single and entangled photons can successfully be sent from one end of the network to the other. Transmitting an entangled photon, means that changing the state of the other photon in the entangled state instantaneously changes the state of the transmitted photon.


Beyond fibre optic networks, satellite networks for quantum communication are also being developed. One example is China’s Micius satellite launched in 2016, which is being used to send quantum data over a distance of 3,800 km between Russia and China[6,7]. Several patents directed toward satellite-to-ground quantum communication have been filed in China including by the State Grid Corporation of China, such as CN112564900 for transmitting quantum encrypted data using quantum channels between a satellite and a ground station.


An industry that will be heavily targeted by quantum hacking attacks is the finance sector and its technologies (Fintech). As such, more secure data encryption for Fintech is being actively developed in preparation for a post-quantum world. Our article ‘Top five patents for Fintech inventions’, explores various patented Fintech technologies including quantum-proof contactless payments.


What developments can we expect in quantum communication?

Optimizing quantum data transmission will likely require hybrid networks that will include both satellites and fibre optic cables. As these networks grow, we will likely see the emergence of a quantum internet[8]. The first shopping transactions over a quantum computing network – or a small quantum internet – have already been carried out in China[9]. To expand such small networks into hybrid global ones, researchers are looking to optimize the number of satellites needed and the ideal height at which these satellites should be placed. In addition to advancements in quantum computing, the technological developments involve simulations of satellites and materials research to improve the composition of fibre optic cables in order to reduce photon loss.


Quantum communication remains an active area of technological development across multiple sectors. As quantum computers evolve, the competition for building wider and more secure quantum networks continues.  


This is the third article in our series on Patenting Quantum Computing in Europe. Our first and second articles are available here.



[1] Quantum Xchange.

[2] The Quantum Insider.

[3] Quantum Corridor.

[4] euNetworks.

[5] euNetworks.

[6] Liao, SK., Cai, WQ., Liu, WY. et al. Satellite-to-ground quantum key distribution. Nature 549, 43 (2017).

[7] South China Morning Post.

[8] Khatri, S., Brady, A.J., Desporte, R.A. et al. Spooky action at a global distance: analysis of space-based entanglement distribution for the quantum internet. npj Quantum Information 7, 4 (2021).

[9] New Scientist.


Continue reading about What is Quantum Computing? Part III
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