Opinion / 22 November 2019, 12:30pm / Louis Fourie
JOHANNESBURG - The first connection to be transmitted over Arpanet - precursor of the Internet - was sent from a computer at the University of California, Los Angeles (UCLA), to a computer at the Stanford Research Institute (SRI) in Palo Alto a little more than 50 years ago.
On the evening of October 29, 1969 researchers at UCLA called their colleagues at SRI and then started to type “LOGIN” on their computer. After each letter, SRI confirmed they had received it. However, when they got to the G the host at SRI crashed. Despite the crash with the third letter, the success of sending data was the beginning of the Internet revolution.
Stephanie Wehner, a German physicist and computer scientist at Delft University of Technology, is one of several scientists trying to create a totally new kind of internet called the “quantum internet.”
The ability to send qubits from one place to another over fibre-optic cables would certainly revolutionise many aspects of science and culture, cyber security and astronomy.
The current internet is a playground for hackers and many vulnerabilities exist despite our best attempts to secure our computers, data and networks. But if quantum physicists succeed in building a quantum network such security weaknesses would be something of the past.
Freed from the limitations of classical networks, the quantum internet could provide a level of privacy and security that is impossible with today's internet.
In a world of cyberthreats, the most famous application of quantum networks is secure communication. Quantum communication is already used for quantum key distribution (QKD) - the creation of secret keys consisting of random strings of zeros and ones. This security will hold even if the attacker has a powerful quantum computer.
In July 2018, Alberto Boaron of the University of Geneva, Switzerland, and colleagues were able to distribute secret keys using QKD over a record distance of more than 400kmof optical fibre at 6.5kilobits per second. But quantum networks will do much more than QKD. The next step is to transfer quantum states directly between nodes.
The security lies in quantum entanglement of two qubits. Entanglement allows for maximum co-ordination even over a distance. To entangle a quantum bit in Cape Town with a quantum bit in Johannesburg, the quantum internet could be used. Once entangled, both systems are described by a single quantum state.
When a measurement is made in both places it would always display the same outcome, even though it was not determined beforehand.
No wonder Albert Einstein called entanglement “spooky action at a distance” since the measuring or copying of one member of an entangled pair of particles seems to instantaneously change the state of its counterpart, even if the counterpart particle is on the other side of the galaxy. The quantum internet is thus very useful for tasks that require co-ordination over a distance, due to the first property of quantum entanglement.
It may seem logical that maximum co-ordination would make the entanglement easy to share with numerous people.
But due to the second property of entanglement it is not possible. The second property of entanglement is that it is inherently private.
If two qubits are entangled over a distance, nothing else can have any share of the entanglement, thus making the communication very secure. Qubits can also be encoded through the polarisation states of a photon or in the spin states of electrons and atomic nuclei.
Wehner and colleagues published a paper in Science in October 2018 describing a six-stage plan to realise the quantum internet. Each developmental stage will support new algorithms and applications. The first stage is already in progress and entails a demonstration quantum network that will connect four cities in the Netherlands.
The quantum internet will make many new applications possible in the years to come. For example, it will make new kinds of remote computing possible. If a company designed a new proprietary material and wanted to test its complex set of attributes in a simulation, it would be best to use a quantum computer instead of a classical computer due to its superior power and speed.
However, as a result of the high cost of quantum computers, not every company could afford a quantum computer and therefore they will have to use quantum-computing services offered by a number of organisations.
The major concern is, however, the confidentiality of the proprietary material design that may be compromised if the simulation is done by an external organisation.
But if a very simple quantum device is used (eg making one qubit at a time) and the qubits are transferred via a secure quantum network to a powerful quantum computer, the simulation can be done on the powerful quantum computer without the quantum computer or its owner learning what the material design entails.
A fully developed quantum network may still be in the future, due to the challenges of reliable quantum memories and the ability to extend the reach of a quantum link to longer distances.
Quantum nodes need sophisticated quantum logic gates to ensure entanglement is preserved.
However, recent breakthroughs in transmitting, storing and manipulating quantum information are very promising and indicate that a proof-of-principle is immanent.