In quantum mechanics, there is the concept of the quantum limit, which, among other things, explains how strongly experimentally you can cool objects. Physicists at the National Institute of Standard and Technology (NIST) have recently been able to cool an object to temperatures below this quantum limit, theoretically proving that the technology they used to do this is also suitable for cooling objects to absolute zero (−273.15 ° C), that is, the state in which matter loses absolutely any energy and movement.
The cooled object in this case was a microscopic "drum", which is a tiny vibrating membrane. The membrane itself looks like a tiny disk with a diameter of 20 micrometers and a thickness of 100 nanometers included in a superconducting electronic circuit. This circuit is designed in such a way that the vibrations of the membrane affect the microwave rays, which are reflected from the electromagnetic cavity. The photons of microwave radiation that fall inside the cavity, change their frequency to that which corresponds to the frequency of oscillations of the membrane itself. As a result, an oscillatory system arises, having a specific resonant frequency.
In earlier experiments, specialists from NIST were able to cool such a membrane to an energy state corresponding to one third of the quantum energy. For this they used the sideband cooling method. Due to a very powerful microwave flow, which has a frequency below the resonant frequency of the system, a charge was created that caused the atoms and molecules in the plate to oscillate at a speed of 10 million times per second, which resulted in the appearance of photons whose frequency was higher than the frequency of the resonant system. When a certain limit for filling with photons was reached in the electromagnetic trough, some photons began to leave the system and at the same time take a piece of energy with them, which led to a very strong cooling of the elements of this system.
In a recent experiment, scientists have achieved a state in which the energy of the membrane after cooling was one-fifth of the energy of a single quantum. This was achieved thanks to the method of "compression" of light. Compression in this case means a quantum-mechanical phenomenon, in which noise and other undesirable oscillations are isolated from the fundamental frequency of light oscillations so as not to affect the course of the experiment. To create this compression, the scientists used a special scheme that acted as a bobbin and a device that produces photons completely devoid of extraneous vibrations.
“The noise present in photons leads to a disturbance in the harmonicity of the system oscillations and, accordingly, to its heating. We were able to squeeze the light to the highest level and received photons with the highest possible at the moment stable intensity. They are strong and fragile at the same time, ”commented NIST physicist John Teufel.
The experiment as a whole proves that objects can be cooled to lower values than predicted by the previously adopted quantum limit (from a theoretical point of view, even to absolute zero). This, in turn, can significantly affect the methods of research and the overall development of technology.
“The lower the objects are cooled, the better it is for many areas. For example, sensors in this case will become even more sensitive and accurate. In the storage environment, this same data can be stored longer. And if you use such a cooling model in quantum computers, this will avoid errors. ”
According to NIST researchers, such cooled “drums” can become qubits (quantum computing elementary particle, quantum bit) of a kind of hybrid quantum computer (based on both quantum and mechanical technologies), which will be able to solve the tasks that currently considered "unsolvable." For the most part, they are unsolvable precisely because of the limitations created by high-temperature conditions, but the proposed method can solve this problem. At least in theory.
The article is based on materials .
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