Experts consider glass nanoparticles kept inside extreme vacuum layers as potential platforms for examining the quantum world's limits. However, a question in the field of quantum theory remains unanswered: at which size does an object start being described by quantum physics laws rather than classical physics laws?
Achieving Quantum-State Cooling in More Than One Direction Is Challenging
SciTechDaily reports that a research team attempted to precisely answer the question through the ERC-Synergy project Q-Xtreme. The team comprised Lukas Novotny from ETH Zurich, Markus Aspelmeyer from the University of Vienna, Oriol Romero-Isart from the University of Innsbruck, and Romain Quidant from Zurich.
A vital step to achieving the goal is to decrease the energy kept in a nanoparticle's motion. In other words, the nanoparticle must be cooled down to the quantum ground-state.
According to Science Daily, the project team has been focusing on nanoparticle ground-state cooling for a while. Many experiments conducted across Zurick and Vienna, which are backed up by theoretical computations made by Dr. Gonzalez-Ballestero and Professor Romero-Isart from the University of Innsbruck, have enabled the first demonstration of nanoparticle ground-state cooling. This was achieved by using electronic control to dampen the motion of the particle or by positioning the particle in between two mirrors. Throughout the experiments, this ground-state was only met in one of the three motion dimensions. Hence, the motion in the other two directions stayed "hot."
To dig deeper into novel quantum physics, it is important to achieve quantum ground-cooling in at least two directions. However, this has remained elusive considering how hard it is to make the mirrors that surround the particle efficiently interact with motion in varying directions. This phenomenon, called the "dark mode effect," inhibited full ground-state cooling.
Scientists Successfully Achieve Quantum-State Grounding of Nanoparticles in 2D Motion
Now, the researchers were able to succeed in quantum-state cooling the nanoparticle in two different motion directions. Their findings were included in the Nature Physics journal.
SciTechDaily reports that a glass sphere that is around one thousand times smaller compared to a sand grain gets fully isolated from the environment in a high vacuum and is held by a focused laser beam as it is cooling, at the same time, close to absolute zero.
With their theoretical predictions, the Swiss scientists successfully circumvented the problem involving the dark state. In doing so, they came up with frequencies wherein the oscillation of the particle was done differently in two directions and adjusted to the laser light's polarization.
Their research shows that it is possible to achieve the minimum energy state across three directions of motion. It also enables fragile quantum states to be created in two different directions. This may, in turn, be used to come up with sensors or gyroscopes that are extremely sensitive.
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