# Quantum uncertainty will secure communications

*This is the second in a series of four articles about how quantum entanglement is changing technology and how we understand the universe around us. In the **previous post**, we discussed what quantum entanglement is and how physicists in the early 1900s developed the idea that nature is uncertain. In this article, we explain how entanglement can transform the way we communicate.*

Quantum entanglement has taught us that nature is weird. Nothing is certain on the quantum scale. We may not know the properties of particles, but that’s not because our instruments aren’t good enough. This is because particles don’t even have defined properties until they are observed. Nature is uncertain, and that uncertainty is woven into the very fabric of the Universe.

You may be thinking: this is all very interesting, but what does it have to do with me?

The fact is — a lot. Quantum entanglement is not just a theory. It has real implications in many areas. Today, we are going to discuss a very practical application: securing our communications.** **By utilizing the inherent uncertainty of the quantum scale, our communications can become faster and more secure, transforming the Internet and the way we do business.

## quantum necessity

Many of the forms of digital communication we use would be considered traditional communications, ranging from the Internet to calls on cell phones. Traditional communications consist of strings of 1s and 0s, each containing a “piece” of information.

Quantum communications are different. Taking advantage of uncertainty at quantum scales, we can let our information be both 1 and 0 simultaneously. This bit of quantum information, or qubit, can be a superposition of states – a 1, a 0 or a combination – until it is observed, at which point its wave function collapses. Due to superposition, qubits can perform more than one calculation at a time and hold more information than their classical counterparts.

Confidentiality in communication is not only nice to have; it is necessary. According to the Identity Theft Resource Center, there were 1,862 data breaches in 2021, compromising nearly 300 million people. There are many sources of these data breaches. Many of them occur when information is transferred. Any communication over the Internet is likely to be intercepted and seen by someone other than the intended recipient.

To protect our privacy, data transferred via conventional communication channels may be encrypted. But the strength of this encryption is balanced by the ingenuity of the hacker. Traditional communication is based on combinations of 1s and 0s. Hackers can look at these 1s and 0s, copy them and send them, without anyone else knowing that the message has been intercepted. The level of security using quantum communication, on the other hand, is rooted in the laws of physics, and it could be immune to hacking using a process called QKD, or quantum key distribution.

Let’s see an example of how this could work. Let’s say we have two people, Alice and Bob. Alice wants to send information to Bob. It uses two methods to transfer data. In the first, it sends conventional encrypted data over a normal communication channel. To decipher the data, Bob would receive a second piece of information from Alice – this time, a quantum message consisting of qubits transferred over a quantum channel. It may include randomly polarized photons. It’s Bob’s quantum key, and he can use it to decode the message. The idea is that the message should only be understood once the classical and quantum data are combined.

Using a quantum key has a few advantages over traditional communications. The uncertain nature of the wave function protects quantum information from eavesdropping, as this type of interference would cause the qubits’ wave function to collapse. It is also impossible for a hacker to intercept, decrypt and retransmit the signal. Indeed, an unknown quantum state cannot be copied. (This is called the no-cloning theorem.) Therefore, if their signal is intercepted, Alice and Bob will know.

## Teleport Info

Of course, things get more complicated in reality. A fraction of the quantum message will be destroyed in transit. For example, a photon that is part of the message can interact with the edge of the fiber optic cable, causing its wave function to collapse. This process is called decoherence.

When Bob receives his key, he will compare it to Alice’s by sampling random qubits to see if it is similar enough. If the error rate is low, chances are the errors are a result of decoherence, so Bob will go ahead and decode his message. If the error rate is high, someone may have intercepted the key. In this case, Alice will generate a new key.

Although it’s much more secure than traditional communications, it’s not perfect. The further the quantum channel is, the higher the risk of decoherence. The message can therefore only travel a few tens of kilometers (in a fiber optic cable) before becoming useless. Quantum repeaters can be used to help. They can decode the message and then re-encode it into a new quantum state, allowing it to travel further.

However, each decode gives hackers an opportunity to catch the message. QKD’s security also assumes that everything works perfectly – and nothing in real life is perfect.

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To increase security, we can turn to quantum entanglement and use a nifty method called quantum teleportation.

In this method, both Alice and Bob have an entangled qubit. Alice uses a third qubit, which she allows to interact with her qubit. As a result, Bob’s entangled qubit immediately takes on the state of Alice’s qubit. Alice then sends the results of the interaction to Bob through a regular channel. Bob can use the results, combined with his qubit, to retrieve the message. This method is more secure because the actual message does not travel between Alice and Bob – there is nothing to intercept.

## The race for quantum communications

Secure networks using QKD are online and growing rapidly. A team in the Netherlands first showed they could reliably transfer data 10 feet away using quantum teleportation in 2014. Three years later, a major quantum communication milestone was reached when a team of Chinese scientists used the Micius satellite to illustrate quantum entanglement over the longest distances. yet reached, between stations more than 1200 km apart.

The size of QKD networks has also increased rapidly. The first was established in Boston by DARPA in 2003. Currently, the largest QKD network is in China, spanning 4,600 km and consisting of optical cables and two ground-to-satellite links. Earlier this year, China launched Jinan 1 – a tiny quantum satellite weighing less than 100 kg, designed to perform quantum key distribution experiments in low Earth orbit. Eventually, quantum communication could prove effective over large distances in space.

Although the technology is still in its infancy, QKD networks have enabled everything from secure bank data transfers to the world’s first quantum-encrypted video call between China and Vienna, Austria. Over time, quantum communications can deliver huge benefits for industries as diverse as banking, security, and the military. We are not at the point where quantum communications can be deployed to protect our internet communications, but we may not be far off.

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