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Quantum tunnels allow particles to break the light-speed barrier

In the fascinating realm of quantum physics, particles seem to defy the laws of classical mechanics, exhibiting mind-bending phenomena that challenge our understanding of the universe. One such phenomenon is quantum tunneling.

In quantum tunnels, particles appear to move faster than the speed of light, seemingly breaking the fundamental rules set by Einstein’s theory of relativity.

Redefining time in the quantum world

However, a group of physicists from TU Darmstadt has proposed a new method to measure the time it takes for particles to tunnel, suggesting that previous experiments may have been inaccurate.

Patrik Schach and Enno Giese, physicists from TU Darmstadt, have published their groundbreaking experiment design in the prestigious journal Science Advances.

Their approach aims to redefine the concept of “time” for a tunneling particle, taking into account the quantum nature of the phenomenon.

First step: Understanding quantum tunnels

Quantum tunneling is a phenomenon in quantum mechanics where a particle, such as an electron, passes through a potential energy barrier that it classically cannot surmount.

In classical physics, if a particle doesn’t have enough energy to overcome a barrier, it will simply bounce back or stop.

However, in quantum mechanics, particles exhibit wave-like properties, and there is a probability that the particle can “tunnel” through the barrier, even if it lacks the energy to cross it classically.

Here are some key points to understand about quantum tunnels:

Wave-particle duality

Particles in quantum mechanics possess both wave and particle properties. The wave nature of particles allows them to exhibit behaviors that are not possible in classical physics.

Quantum tunnels and probability

The probability of a particle tunneling through a barrier depends on factors such as the barrier’s width and height, and the particle’s energy.

Energy conservation

Quantum tunneling does not violate the law of energy conservation. The particle does not gain or lose energy while tunneling. Instead, it appears on the other side of the barrier with the same energy it had before.

Applications for quantum tunnels

Quantum tunneling has numerous practical applications, including scanning tunneling microscopy (STM), which allows scientists to image surfaces at the atomic level, and flash memory drives that use quantum tunneling to store and access data.

Radioactive decay

Quantum tunneling also plays a role in radioactive decay, where particles escape the nucleus of an atom despite not having enough energy to overcome the nuclear potential barrier.

Dual nature of particles

According to quantum physics, small particles such as atoms or light particles possess a dual nature, behaving like both particles and waves depending on the experiment.

As mentioned previously, quantum tunneling highlights the wave nature of particles, where a “wave packet” rolls towards an energy barrier, and a small portion of it penetrates the barrier, resulting in a probability that the particle will appear on the other side.

“But the particle does not follow a path in the classical sense,” objects Enno Giese. “It is impossible to say exactly where the particle is at a particular time. This makes it difficult to make statements about the time required to get from A to B.”

Using particles as clocks

Inspired by Albert Einstein’s quote, “Time is what you read off a clock,” Schach and Giese propose using the tunneling particle itself as a clock, with a second non-tunneling particle serving as a reference.

By comparing these two natural clocks, they aim to determine whether time elapses slower, faster, or equally fast during quantum tunneling.

The researchers suggest using atoms as clocks, taking advantage of the oscillating energy levels within them. By addressing an atom with a laser pulse, its levels initially oscillate in sync, starting the atomic clock.

During tunneling, the rhythm shifts slightly, and a second laser pulse causes the two internal waves of the atom to interfere. Detecting this interference allows for precise measurement of the elapsed time.

“The clock that is tunneled is slightly older than the other,” says Patrik Schach, contradicting experiments that attributed superluminal speed to tunneling.

Pushing the boundaries of experimental physics

While the proposed experiment can be carried out with today’s technology, it presents a significant challenge for experimenters. The time difference to be measured is extremely short, around 10-26 seconds.

To overcome this, the researchers suggest using clouds of atoms as clocks instead of individual atoms and amplifying the effect by artificially increasing the clock frequencies.

“We are currently discussing this idea with experimental colleagues and are in contact with our project partners,” adds Giese. The possibility of a team deciding to carry out this exciting experiment in the near future is quite real.

Understanding how time works in quantum tunnels

In summary, Patrik Schach and Enno Giese’s experiment design challenges our understanding of time and particle behavior in the quantum realm.

By proposing a new method to measure the time it takes for particles to tunnel, they are questioning previous assumptions about superluminal speeds and presenting new avenues for exploring the mysteries of quantum physics.

As they collaborate with experimental colleagues and project partners, the possibility of conducting this exciting experiment draws closer, promising to unlock the secrets of the quantum universe and pave the way for a deeper understanding of the fundamental nature of reality.

The full study was published in the journal Science Advances.


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