Large Quantum Networks

Overview:

Quantum technologies are going to play an important role in future in multiple dimensions. Quantum computers have started proliferating to solve some of the hardest problems which are difficult for even classical supercomputers as were demonstrated by the Quantum Supremacy experiments in the last 5 years. Several problems, which are virtually impossible to solve on a classical computer since the solution space grows exponentially with input size, are being solved by quantum computers. Primarily two types of quantum computing have been implemented, namely circuit based and adiabatic approaches. Quantum machine learning promises to add one  more area in quantum computing which helps in dealing with high dimension data. Also, with the advent of quantum computers, many classical cryptographic methods, RSA, are likely to fail. Hence, post-quantum cryptography and quantum cryptography are likely to provide quantum-safe security solutions. Quantum Key Distribution (QKD) is one such method where the cryptographic keys are generated through a quantum channel.

The vision of a quantum internet holds promise for transforming communication and computation in ways that were previously unimaginable. While the classical internet has undoubtedly revolutionized the world, it also faces challenges such as cybersecurity threats, etc., and limitations in computational power for certain tasks. Quantum internet offers solutions to some of these challenges. One of the most significant advantages of a quantum internet will be  its inherent security features. Quantum cryptography exploits the property that when ‘a’ quantum state is measured, you cannot get back ‘that’ quantum state and offers unbreakable encryption, offering a level of security that is theoretically impossible to breach using classical methods. Furthermore, quantum communication enables the distribution of quantum entangled particles over long distances. This phenomenon, known as quantum entanglement, allows for instantaneous communication between particles regardless of the distance separating them. Quantum entanglement over large distances, combined with quantum teleportation has the potential to  revolutionize fields such as secure communication and  distributed computing. Moreover, there exist several qubit generation technologies ranging from ion-traps to superconducting methods to recently invented semiconducting methods,  which can perform computations at an exponentially higher speed than classical computers. These technologies   could further augment the capabilities of the quantum internet provided we step up the research in the area of quantum  communication and transmit and receive the computed data with high fidelity and without losses. Distributed quantum computing, facilitated by a quantum internet, could then enable collaborative processing of vast amounts of data and solve complex problems that are currently beyond the reach of classical computing, in areas such as computational chemistry, drug discovery, weather and climate modelling etc..

However, the development of a quantum internet is still in its infancy, and numerous technical challenges must be overcome before it becomes a reality. The primary problem that arises in the transmitting of the qubits over large distances  is ‘decohorence’ due to which the data is lost to the environment, without reaching the intended destination.  Although, significant progress is being made in research laboratories around the world, several open problems  exist in this area of quantum communication.  Efficient qubit generation, efficient entanglement generation and distribution, development of quantum hardware such as  memories and  repeaters (to overcome decoherence) ,  computing hardware and interfaces with classical hard ware etc. on the device side; development of quantum network layers, respective  protocols and their integration with existing communication network  infrastructure on the protocol front are some of the important areas, that are worth mentioning .

It is important to note that a quantum node is a combination of  a quantum computer (a qubit generator, entanglement generator and some computing hardware and interfaces),  a quantum channel, a classical channel , quantum memories and repeaters and an arrangement to purify entanglement.  It is thus obvious, that  Quantum Internet  / large quantum networks will be formed from combining  such quantum nodes in various topologies.

Our work till date has been  in the area of protocol development for large quantum networks, assuming that quantum nodes as mentioned above are available.  We have written a code and are performing simulations that can emulate behaviour patterns in  large scale quantum networks.  The following is a summary of our work so far.