Quantum ‘Jamming’ May Help Unlock the Mysteries of Causality

The original version about This article appeared inside Quanta Magazine.

Over the past few decades, researchers have come to understand that quantum computers must be capable breaking down the most commonly used codes which is very protective of the digital world. To protect themselves from this disaster, they have spent years creating new codes that seem to exist safe from future safeguards with quantum computers.

At the same time, they made it again smart ways using the laws of quantum mechanics to keep communications secure. But quantum mechanics, like the “classical” mechanics that preceded it, is a theory of nature. What if it will be replaced by a more complete theory, just as mechanics replaced Newtonian physics a century ago? Will this multi-channel communication system still be secure in a country with strict laws?

“Given these privacy protocols, it’s best to be skeptical,” he said Ravishankar Ramanathanan expert at the University of Hong Kong who works on quantum cryptography. Let’s imagine that in the future people will realize that quantum mechanics is not a true theory of nature.

It’s a possibility worth considering. The complexity of major problems – such as reconciling quantum mechanics and gravity – suggests that a post-quantum theory of the universe may include something unexpected.

In order to avoid the possibility that their protocols are based on faulty assumptions, some quantum cryptographers explore some important building blocks. Instead of starting from quantum mechanics, he digs deeper, to the concept of causality.

Hidden Damage

One way to understand what’s going on in this area is to think about quantum key distribution, which involves using the laws of quantum mechanics to pass a key—something that can be used to identify a secret message—in a way that cannot be secretly compromised. Quantum key distribution uses quantum entanglement, which locks two particles together through one of their properties, such as spin. Quantum entanglement has something of a tripwire. If someone tries to tamper with the noise—as they would if they tried to steal the keys—the hack will destroy the noise, revealing the damage. This is because of an important principle of quantum mechanics called “monogamy of entanglement.”

But what if this principle no longer applies? In such cases, if the people sending the message do not have full control of their devices, an outsider can subtly change the blocking of the particles, disrupting the communication without losing any details.

This process is called quantum jamming, and efforts to understand it have increased in recent years.

For many scientists, entanglement is exciting because it can help them better understand quantum mechanics and how it starts and ends. They ask themselves: Are there deep principles that prohibit exercise, that make it impossible? Or, if there is no stopping point, can jamming occur in the real world?

Jim the Jammer

Michael Ecksteina physicist at the Jagiellonian University in Krakow, Poland, likes to explain things clearly. Its protagonists are classic characters from the description of quantum mechanics, Alice and Bob.

“Let’s say you have Alice and Bob, and they meet a magician, Jim the Jammer,” Eckstein said. “The magician says, ‘I have two balls, one is white, the other is black.’

The balls represent the trapped particles. If the particles are small, we have something that is connected in some way – if you try the first part and find that its spin is up, for example, the spin of the other particle will be down, and vice versa. This is true even of a particle in the center of the universe. Here the balls are connected so that if one is white, the other is always black.