When light and atoms share a common baby

A particularly inconvenient feature of oceanic mechanics is that one event can be in a high-stakes state – happening here and there, or present and future.

It is difficult to create such a situation, as they are destroyed if information of any kind about the place and time of the incident jumps into the surrounding area – and even if no one registers. this information. But when superpositions occur, they lead to ideas that are very different from classical physics ideas, questioning down to our true understanding of space and time.

Scientists from EPFL, MIT, and CEA Saclay, publish in Science Advances, reveal the state of simultaneous vibration at two different times, and reflect this quantum state by measuring the strongest class of quantum correlations between light behaviors that interact with the vibration.

The researchers used a very short laser-pulse to induce a specific pattern of vibration within a diamond crystal. Each pair of adjacent atoms oscillated like two springs connected by a spring, and this oscillation was parallel throughout the entire clear region. To conserve energy through this process, light of a new color is emitted, shifted toward the red of the spectrum.

This classic picture, however, is inconsistent with the experiments. Instead, both light and vibration should be defined as particles, or quanta: light energy is measured in individual photons while vibration energy is measured to separate photons (named after the ancient Greek “photo = light” and “phono = sound”).

The process described above should therefore be seen as the cooling of an incoming photon from the laser into a pair of photons and a phonon – similar to a nuclear diffusion. atom in two smaller pieces.

But it is not the only shortcoming of classical physics. In quantum mechanics, particles can be in a state of high standing, such as the famous cat Schrödinger alive and dead at the same time.

Even more counterintuitive: two bases can interfere, losing their respective. The same information that can be gathered about them applies to their common connections. Because both bases are defined by a common state (wavelength), these correlations are stronger than is possible in classical physics. It can be determined by performing an appropriate measurement on both bases. If the products break a classic boundary, one can be sure that they have been imported.

In the new study, EPFL researchers were able to engage the photon and phone (i.e., light and vibration) emitted in the incoming laser photon uniform crystal. To do this, the scientists designed an experiment in which the photon-phonon pair could be formed at two different locations. Classically, there would be a situation where the pair is formed at time t1 with a 50% probability, or at a later time t2 with a 50% probability.

But here comes the “trick” played by the researchers to generate a captured state. With a precise adjustment of the experiment, they ensured that even the weakest trace of the formation time of a light vibration pair (t1 vs. t2) was not left in the universe. In other words, they deleted information about t1 and t2. Quantum mechanics then predicts that the phonon-photon pair will engage, and that it is in the real-time position of t1 and t2. This prediction was beautifully confirmed by the measurements, which yielded results that did not correspond to the classical proof theory.

By showing a link between light and vibration in a crystal that a person could hold in his finger during the experiment, the new study creates a bridge between our everyday experience and the intriguing range of quantum mechanics.

“Quantum technologies are being touted as the next technological revolution in computing, communications, sensing,” says Christophe Galland, head of the EPFL’s laboratory for Quantum and Nano-Optics and one of the study’s lead authors. “They’re currently being developed by major universities and major companies around the world, but the challenge is daunting. Technologies like this rely on very fragile quantum effects that last only at extreme cold temperatures or high temperatures. Our study shows that even common materials at environmental conditions can produce the fine quantum properties necessary for the maintenance of quantum technologies, however, there is a price to pay: the quantum bonds maintained are up to atomic vibrations in the crystal lost after just 4 picoseconds – ie, 0.000000000004 seconds! Useful tool – work for future quantum engineers. ”



Santiago Tarrago Velez, Vivishek Sudhir, Nicolas Sangouard, Christophe Galland. The relationship of a bell between light and vibration at environmental conditions. Advances in science 18 Dec 2020, 6: eabb0260.

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