Combining Six Oscillators Can Change The Quantum World

Top researchers at EPFL have found a way to combine the power of six mechanical oscillators into one collective state. This is considered a big breakthrough because this will allow the development of ultra-precise sensors and other components crucial for large-scale quantum systems.

Mechanical oscillators are devices found in many everyday tools and technologies. They have the ability to produce precise, repetitive motion by converting kinetic energy into potential energy and vice versa.

An example of this is the pendulum in your wall clock that swings back and forth. Springs and pistons are another example. However, so far, these macroscopic oscillators have been used for regular applications. Scientists want to use them for quantum systems.

This is because "controlling mechanical oscillators at the quantum level is essential for developing future technologies in quantum computing and ultra-precise sensing," the study authors note.

Previous research works have focused on using a single mechanical oscillator for quantum systems. This approach works well for small-scale applications, such as quantum squeezing (a technique to reduce uncertainty in one aspect of a system) or ground-state cooling (cooling the system to its lowest energy state).

However, powerful large-scale quantum systems "demand exceptionally precise control over multiple oscillators with nearly identical properties," according to the EPFL team. This is where findings from the new study could help.

The researchers used a technique called sideband cooling. It involves the use of a laser to cool atoms and ions to their ground state. When this laser is applied to an oscillator, it brings down the thermal vibrations in the system, causing it to become still.

Using this technique, the study authors turned six individual oscillators into a collective system, a hexamer. They also linked the oscillators to a microwave cavity that allowed the oscillators to interact more effectively.

"More interestingly, by preparing the collective mode in its quantum ground state, we observed quantum sideband asymmetry, which is the hallmark of quantum collective motion. Typically, quantum motion is confined to a single object, but here it spanned the entire system of oscillators," explained Marco Scigliuzzo, study co-author and a postdoc researcher at EPFL.