Vibration state which is simultaneous at two different times

While lights and atoms share a common vibe

A particularly counter-intuitive feature of quantum mechanics is that a single event can exist in a state of superposition – both here and there, or both today and tomorrow.

Such superpositions are difficult to create, as they are destroyed if any information about the place and time of the event is leaked to the surrounding area – and even if one does not actually record this information. But when superpositions occur, they lead to observations that are very different from classical physics, questioning our understanding of space and time below.

EPFL scientists, MIT, And CEA Secle, publishing Science progress, Demonstrating the state of vibration that is present at two different times simultaneously, and proving this quantum superposition by measuring the strongest class of quantum correlation between light beams exposed to vibration.

The researchers used a very short laser-pulse to initiate a specific pattern of vibration inside the diamond crystal. Each pair of neighboring atoms is oscillated like two masses connected by a spring, and this oscillation was in harmony throughout the illuminated region. During this process, for the storage of energy rays, new colored light is emitted, turning to red of the spectrum.

This classical picture, however, is inconsistent with the experiments. Instead, both light and vibration should be described as particles or quanta: light energy radiation is converted to discrete photons while vibrational energy radiation is measured in independent phonons (named after the ancient Greek “photo = light” and “phono = sound”).

The process described above should be viewed as the splitting of a photon from a laser into a pair of photons and phonons – similar to atomic splitting. Atom In two small pieces.

But it’s not just a lack of classical physics. In quantum mechanics, particles can exist in a microscopic state, just as the famous Sreedinger cat is alive and dead at the same time.

Even more hostile: two particles can get trapped, losing their personality. The only information that can be gathered about them is their general relationship concerns. Because both particles are described by the normal state (wave function), this correlation is stronger than is possible in classical physics. It can be represented by proper measurement on two particles. If the results violate the classical limits, one can be sure that they were trapped.

1. A laser produces a very short pulse of light 2. A fraction of this pulse is sent to a nonlinear device to change its color. 3 .. The two laser pulses again overlap on the same path, forming a pair of “text and read”. Beans. Each. Each pair is divided into short and long way, 5 .. “early” and “late” get time slots, overlap once again. Inside the diamond, during the “initial” time slot, a photon can generate a “write” pulse vibration, while a photon from the “read” pulse converts the vibration back into light. The. The same sequence can be used during the “late” slot. But in this experiment, the scientists made sure that only one vibration is stimulated total (in both the early and late slots). 8. Again it is impossible to distinguish the late moment from the onset of vibration by lapping the photon over time. The vibration is now in the early and late time quantum superposition. 9. In the detection device, the “write” and “read” photons are separated according to their colors, and analyzed with single-photon counters to reveal their spread. Credit: Santiago Terrago Velez (EPFL)

In a new study, EPFL researchers managed to trap photons and phonons (i.e., light and vibration) produced in the fission of laser photons inside crystals. To do this, the scientists designed an experiment in which a photon-phonon pair could be formed at two different instantaneous times. Classically, it will result in a situation with t0% probability paired over time, or with a 50% probability in subsequent t2.

But here comes a ‘trick’ that is played by researchers to create a trapped situation. Through precise configuration of the experiment, they ensured that there was no unprecedented trace of light-vibration pair formation time (T1 vs. T2) left in the universe. In other words, they erased information about T1 and T2. Quantum mechanics then predicts that the phonon-photon pair will be trapped, and that time exists in the superposition of T1 and T2. This prediction was beautifully confirmed by the criteria, which gave results inconsistent with the classical probability theory.

By showing the flower between light and vibration in a crystal that a person can hold in his finger during the experiment, the new study builds a bridge between our daily experience and an interesting field of quantum mechanics.

“Quantum technologies are being described as the next technological revolution in computing, communication, and sensing,” says Christophe Galland, head of the EPFL’s Laboratory of Quantum and Nano-Optics and one of the lead authors of the study. “They are currently being developed by top universities and large companies around the world, but the challenge is daunting. Such techniques rely on very delicate quantum effects only at very cold temperatures or under vacuum vacuum. Our study shows that even common materials in the surrounding conditions can sustain the delicate quantum properties required for quantum technologies. There is a price to pay, though: the quantum correlation sustained by atomic vibrations in a crystal is lost only after 4 picoseconds – that is, 0.000000000004 of a second! This short time scale, however, is also an opportunity to develop ultrafast quantum technologies. But more research is ahead to transform our research into a useful device – the work for future quantum engineers. ”

Reference: “Bell Correlation between Light and Vibration on Ambient Conditions”, by Santiago Tarrago Velez, Vivishek Sudhir, Nicholas Sangouard and Christoph Galland, 18 December 2020, Science progress.
DOI: 10.1126 / sciadv.abb0260