All this may sound like a science fiction concept, but the creation of quantum networks is a key goal of many countries around the world. The U.S. Department of Defense (doe) recently released a first-of-its-kind plan outlining a step-by-step strategy that will make the dream of a quantum Internet come true, at least in very preliminary form, over the next few years.
The US has joined the EU and China in showing great interest in the concept of quantum communication. But what is the quantum Internet, how does it work, and what wonders can it do?
WHAT IS THE QUANTUM INTERNET?
The quantum Internet is a network that will allow quantum devices to exchange some information in an environment that obeys the strange laws of quantum mechanics. In theory, this would provide the quantum Internet with unprecedented capabilities that cannot be realized with modern web applications.
In the quantum world, data can be encoded as qubits, which can be created in quantum devices such as a quantum computer or a quantum processor. simply put, the quantum internet will involve sending qubits over a network of multiple quantum devices that are physically separated. most importantly, all of this would be due to strange properties unique to quantum states.
This may sound like a standard Internet connection. But sending qubits through a quantum channel, rather than a classical one, essentially means exploiting the behavior of particles at their smallest scale – the so-called “quantum states” that have caused excitement and alarm among scientists for decades. And the laws of quantum physics that underlie how information will be transmitted on the quantum Internet are nothing but unfamiliar. In fact, they are strange, illogical, and at times even seem supernatural.
So, to understand how the Internet 2.0 quantum ecosystem works, you can forget everything you know about classical computing. Because little of the quantum Internet will remind you of your favorite web browser. in short, not much that most users are used to. So, at least for the next few decades, you shouldn’t expect to ever be able to switch to quantum Zoom meetings.
Central to quantum communication is the fact that qubits that use the fundamental laws of quantum mechanics behave very differently from classical bits. when encoding data, the classical bit can actually be in only one of two states. Just like a light switch must be on or off, and just like a cat must be dead or alive, the bit must be either 0 or 1.
Not so much… Instead, qubits overlap: they can be 0 and 1 at the same time, in a special quantum state that does not exist in the classical world. It’s a bit like being able to be both to the left and right of the sofa at the same time. The paradox is that a simple measurement of a qubit means that it is assigned a state. The measured qubit automatically exits the double state and is converted to 0 or 1, like a classic bit. This whole phenomenon is called superposition and is the basis of quantum mechanics.
Unsurprisingly, qubits can’t be used to send familiar data, such as emails and WhatsApp messages. But the strange behavior of qubits opens up huge opportunities for other, more niche applications.
One of the most exciting areas that researchers armed with qubits are exploring is security. when it comes to classical communication, most of the data is protected by distributing a shared key between the sender and receiver, and then using that shared key to encrypt the message. the receiver can then use its key to decode the data on its side.
The security of most classical communications today is based on an algorithm for creating keys that are difficult for hackers to crack, but not impossible. That’s why researchers are trying to make this communication process “quantum”. this concept is at the heart of an emerging field of cybersecurity called quantum key distribution (qkd). qkd works when one of the two parties encrypts part of the classical data by encoding the cryptography key into qubits. the sender then passes these qubits to another person who measures the qubits to get the key values.
The measurement results in the collapse of the qubit state; but the value that is read during the measurement is important. A qubit, in a sense, is only needed to transmit a key value. More importantly, QKD means that it is easy to know if a third party has intercepted qubits during transmission, as an attacker could cause the key to be destroyed just by looking at it.
If a hacker looked at the qubits at any point during their sending, it would automatically change the state of the qubits. a spy will inevitably leave a trail of eavesdropping – which is why cryptographers claim that qkd is “provably” secure.
QKD technology is at a very early stage. The “normal” way to create a QKD at the moment is to send qubits unidirectionally to the receiver over fiber-optic cables; but this significantly limits the efficiency of the protocol. Qubits can easily get lost or scattered over a fiber-optic cable, which means that quantum signals are very error-prone and have difficulty traveling long distances. In fact, current experiments are limited to a range of hundreds of kilometers.
There is another solution, and it lies at the heart of the quantum Internet: to use another property of the quantum, called entanglement, to communicate between two devices: when two qubits interact and become entangled, they have certain properties that depend on each other. As Long as the qubits are in an entangled state, any change in one particle in the pair will lead to changes in the other, even if they are physically separated.
Thus, the state of the first qubit can be “read” by looking at the behavior of its entangled counterpart. That’s right: even Albert Einstein called it all ” creepy action at a distance.”
And in the context of quantum communication, entanglement can actually teleport some information from one qubit to the entangled other half without the need for a physical channel connecting the two qubits during transmission.
HOW DOES ENTANGLEMENT WORK?
The very concept of teleportation entails, by definition, the absence of a physical network bridge between interacting devices. But what remains is that entanglement must first be created and then maintained. To perform QKD using entanglement, you need to create the appropriate infrastructure to first create pairs of entangled qubits, and then distribute them between the sender and receiver. This creates a “teleportation” channel through which cryptography keys can be exchanged.
In particular, after the entangled qubits have been generated, you must send half of the pair to the key recipient. An entangled qubit can travel, for example, over fiber-optic networks; but they can’t maintain cohesion after about 60 miles. Qubits can also be kept entangled over long distances via satellite, but covering the planet with cosmic quantum devices is expensive.
Thus, there are still huge engineering challenges to create large-scale “teleportation networks” that could efficiently link qubits around the world. When the entanglement network is created, the magic begins: bound qubits no longer need to pass through any physical infrastructure to deliver their message.
Thus, during transmission, the quantum key will be virtually invisible to third parties, impossible to intercept and reliably “teleport” from one endpoint to another. This idea will resonate in industries that deal with sensitive data, such as banking, medical services, or air travel. And it is likely that governments with top-secret information will also be the first to adopt this technology.
WHAT ELSE CAN QUANTUM INTERNET DO?
“Why bother with obfuscation?” you might ask. In the end, the researchers could simply find ways to improve the “normal” connection… Quantum repeaters, for example, could significantly increase the communication range in fiber-optic cables without going so far as to entangle qubits. And that’s without considering the huge potential that entanglement can have for other applications. qkd is the most frequently discussed example of what the quantum internet can achieve, because that this is the most accessible application of this technology. But security is far from the only area causing a stir among researchers.
The entanglement network used for QKD can also be used, for example, to provide a reliable way to create quantum clusters from entangled qubits located in various quantum devices. Researchers won’t need particularly powerful quantum hardware to connect to the quantum Internet – in fact, even a single-qubit processor can handle the task. But by combining quantum devices, which in their current form have limited capabilities, scientists expect that they will be able to create a quantum supercomputer that will surpass them all.
Thus, by connecting many smaller quantum devices together, the quantum Internet can begin to solve problems that are currently impossible to solve with a single quantum computer. This includes accelerating the exchange of huge amounts of data and conducting large-scale sounding experiments in astronomy, material discovery, and life sciences.
For this reason, scientists are convinced that we could take advantage of the quantum Internet before tech giants like Google and IBM even reach quantum supremacy – the point where a single quantum computer solves a problem that is unsolvable for a classical computer.
Google and IBM’s most advanced quantum computers currently contain about 50 qubits, which in itself is far less than necessary to perform the phenomenal calculations needed to solve the problems that quantum research hopes to solve.
On the other hand, connecting such devices through quantum entanglement can lead to the formation of clusters worth several thousand qubits. For many scientists, creating such computing power is actually the ultimate goal of a quantum Internet project.
What can’t quantum internet do?
In the foreseeable future, the quantum Internet will not be used to exchange data in the way we currently do on our laptops. Imagining a generalized, mass-scale quantum Internet would require anticipating several decades (or more) of technological advances. no matter how much scientists dream about the future of the quantum internet, it is impossible to draw parallels between the project in its current form and the way we browse the internet every day.
Today, many studies of quantum communication are devoted to finding ways to best encode, compress, and transmit information using quantum states. Quantum states, of course, are known for their extraordinary density, and scientists are confident that a single node can teleport a large amount of data.
But the type of information that scientists are going to send over the quantum internet has little to do with opening a mailbox and looking at emails. and in fact, replacing the classic internet is not what the technology intended to do.
Rather, the researchers hope that the quantum internet will be next to the classical internet and will be used for more specialized applications. the quantum internet will perform tasks that can be performed on a quantum computer faster than on classical computers, or that are too difficult to perform even on the best supercomputers available today.
And what are we waiting for?
Scientists already know how to create coupling between qubits, and they’ve even successfully used coupling for QKD.
China, a longtime investor in quantum networks, has broken records for entanglement caused by satellites. Chinese scientists recently established entanglement and reached QKD at a record 745 miles.
However, the next step is scaling the infrastructure. All experiments so far were linked only to the two endpoints. Now that point-to-point communication has been achieved, scientists are working to create a network where multiple senders and multiple recipients can exchange data over the quantum Internet on a global scale.
Basically, the idea is to find the best ways to produce on-demand lots of entangled qubits over large distances and between lots of different points at the same time. This is much easier said than done: for example, to maintain communication between a device in China and a device in the US, you will probably need an intermediate node on top of the new routing protocols.
And countries choose different technologies when it comes to establishing entanglement in the first place. While China is opting for satellite technology, fiber is the method favored by the U.S. Department of Energy, which is now trying to build a network of quantum repeaters that can increase the distance separating entangled qubits.
In the US, particles remain entangled through an optical fiber on a 52-mile “quantum loop” in the suburbs of Chicago, without the need for quantum repeaters. The network will soon be connected to one of the Department of Energy’s laboratories to create an 80-mile quantum test bed.
In the EU, the Quantum Internet Alliance was formed in 2018 to develop a quantum Internet strategy, which last year demonstrated entanglement at a distance of more than 31 miles.
For quantum researchers, the goal is to first scale networks to the national level, and one day even to the international level. the vast majority of scientists agree that this is unlikely to happen before a couple of decades. the quantum internet is without a doubt a very long-term project, and many technical obstacles still remain in its path. but the unexpected results that the technology will inevitably bring will be an invaluable scientific journey with many outlandish quantum applications that at the moment are even impossible to predict.