Scientists at TU Wien, Vienna, have made a groundbreaking discovery about the speed of quantum entanglement, one of the fastest processes in nature. By using special tricks and computer simulations, they were able to investigate this phenomenon on an attosecond scale, which is a billionth of a billionth of a second.
According to Prof. Joachim Burgdörfer from the Institute of Theoretical Physics at TU Wien, when two particles are quantum entangled, it’s impossible to describe them separately, and they only have common properties. Researchers led by Prof. Iva Březinová used intense laser pulses to rip an electron out of an atom and shift another electron into a state with higher energy, creating quantum entanglement between the two electrons.
They found that the “birth time” of the flying electron is related to the state of the remaining electron, and this correlation can be measured in experiments. This breakthrough could have significant implications for our understanding of quantum physics and its applications in fields like quantum cryptography and computing.
The Speed of Quantum Entanglement: Unraveling the Fastest Process in Nature
Quantum entanglement is a phenomenon that has fascinated scientists for decades, and recent research has shed light on its incredibly fast emergence. A team of scientists from TU Wien (Vienna) has demonstrated that using special techniques, this process can be investigated on an attosecond scale.
The Emergence of Quantum Entanglement
Quantum theory describes events that occur on extremely short time scales, often regarded as “momentary” or “instantaneous.” However, researchers have now developed computer simulations to investigate the temporal development of these effects. This has enabled them to uncover how quantum entanglement arises on a time scale of attoseconds.
In experiments with entangled quantum particles, scientists typically aim to maintain this entanglement for as long as possible, such as in applications like quantum cryptography or quantum computers. In contrast, the researchers at TU Wien focused on understanding how entanglement develops in the first place and which physical effects play a role on extremely short time scales.
The Role of Laser Pulses in Entanglement
The research team examined atoms hit by an extremely intense and high-frequency laser pulse. This process tears out one electron from the atom, causing it to fly away. If the radiation is strong enough, a second electron can also be affected, shifting into a state with higher energy.
After the laser pulse, one electron flies away, while the other remains with the atom in an unknown energy state. The researchers demonstrated that these two electrons become quantum entangled, meaning they can only be analyzed together. Performing a measurement on one electron allows scientists to learn something about the other electron simultaneously.
The “Birth Time” of Electrons and Quantum Entanglement
The research team employed a suitable measurement protocol combining two different laser beams to show that it is possible to achieve a situation where the “birth time” of the flying electron (i.e., the moment it left the atom) is related to the state of the remaining electron. These two properties are quantum entangled.
This means that the birth time of the flying electron is not known in principle, existing in a quantum-physical superposition of different states. The answer to this question does not exist in quantum physics, but it is linked to the undetermined state of the remaining electron. If the remaining electron is in a higher energy state, the flying electron was more likely torn out at an earlier point in time; if the remaining electron is in a lower energy state, the “birth time” of the free electron was likely later – on average around 232 attoseconds.
The Temporal Structure of “Instantaneous” Events
The research highlights that it is not sufficient to regard quantum effects as “instantaneous.” Important correlations only become visible when one manages to resolve the ultra-short time scales of these effects. The electron does not simply jump out of the atom; instead, it is a wave that spills out of the atom, taking a certain amount of time.
It is precisely during this phase that entanglement occurs, and its effect can then be precisely measured later by observing the two electrons. This work demonstrates that resolving these ultra-short time scales is crucial for understanding quantum effects and their applications in fields like quantum computing and cryptography.
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