Credits: TU DelftWhy does quantum mechanics work so well for microscopic objects, but macroscopic objects are described by classical physics?…
Credits: TU Delft
Why does quantum mechanics work so well for microscopic objects, but macroscopic objects are described by classical physics? This question has disturbed physicists since the development of quantum theory over 1
00 years ago. Researchers at Delft University of Technology and the University of Vienna have now designed a macroscopic system that shows anchoring between mechanical phonons and optical photons. They tested the entanglement with a Bell test, one of the most convincing and important tests to show that a system behaves classically.
From its beginning over 100 years ago, physicists realized that quantum theory could contradict some of the basic axioms of classical physics. In particular, the principles are that information can be exchanged faster than the speed of light (called “locality”) and whether physical quantities exist whether or not they are observed (called “realism”). Albert Einstein once famous, Abraham Pais, his cinema, asked if he really thought that the moon was only when he saw it.
An arguable debate between Einstein and Niels Bohr on the conflict of this axiom in the 1930s began decades of research on the correlations between maternal systems. This phenomenon, called quantum entanglement, quickly crystallized as one of the most important predictions of quantum mechanics. The work of John Bell in the 1960s opened a route to test these principles experimentally, giving new and exciting results to the debate. However, most quantum experiments performed so far are about one or a relatively small number of particles.
A team of researchers led by Professor Simon Gröblacher of Delft University of Technology has now come across a whole new scale of quantum measurements. They created a device that provided correlations between the vibration motion of silicon optoelectronic oscillators, including about 10 billion atoms and optical modes. The devices were cooled to their moving state in a dilution refrigerator and then examined with laser pulses. Specific laser frequencies can interact with the devices, either exciting motion in a controlled manner or reading out its state. When this happens, correlations between the scattered light and the devices make it possible to perfectly predict one of them in another way.
To test whether the correlations in their system were actually quantum mechanics at work, and not classical physics, they performed a clock test. The two particles were presented essentially with a choice: The experiment was designed in such a way that each one could be registered in one of two detectors. Both results were as likely through design, which made it impossible to predict the results for photons or phonons individually. However, due to the correlations between the two, the phonons can be made so that they always give a corresponding measurement result to the photons. In about 80 percent of cases, they were found to be way above the classic Bell threshold of about 70 percent.
The actual Bell test was to tweak some experimental parameters that affect the two particles in different ways and see when this addiction is broken down. Quantum mechanically, the two can maintain correlated measurement results for much longer than is classically allowed. “This is the most thorough test of a massive device that performs quantum mechanically but still performs,” says Prof. Groblacher.
These results mean that the quantum mechanics extend up to the macroscopic domain. In addition, the device manufactured by the manufacturers can be enlarged and improved. Gröblacher: “Because our experimental protocols are independent of the size of the oscillator, these results are the basis for the possibility of searching the boundary between classical and quantum physics with any large objects, even visible to the naked eye.”
Trace the mystery of entangled light particles
Igor Marinković *, Andreas Wallucks *, Ralf Riedinger, Sungkun Hong, Markus Aspelmeyer and Simon Gröblacher, A Optomechanical Bell Test, Phys. Reef. Lett. 121, 220404 (2018). doi.org/10.1103/PhysRevLett.121.220404
Synopsis in Physics : physics.aps.org/synopsis-for/1 … ysRevLett.121.220404