Innovative System to Amplify Signals with Lowest Noise Levels

Researchers at EPFL have collaborated with a University of Basel scientist to propose a theoretical system for amplifying signals with very low levels of noise.

Signal amplification is essential in many technological areas, however, it requires fine-tuning the amount of noise allowed in order to avoid obscuring the actual signal.

This fine tuning is difficult in weak signals. Quantum mechanics has set a noise limit that is even lower than that can be allowed by amplifying devices. Developing such amplifiers remains a challenge.

Tobias Kippenberg and other researchers at the Laboratory of Photonics & Quantum Measurements in EPFL partnered with a Basel University scientist for developing the system.

They used a nano-mechanical oscillator – which is a small moving drum, and two superconducting microwave cavities. These cavities are metallic structures that restrict electromagnetic waves within the microwave spectrum. When the drum moves, the resultant mechanical motion modulates the frequency of these cavities.

In the first microwave cavity, by confining the microwave photons, the nano-mechanical oscillator’s movement is restrained. This makes them so quiet that ‘noise’ resulting due to fluctuations of temperature is eliminated.

The signal that needs to be amplified is contained in the second microwave cavity. The interaction that takes place between the nano-mechanical oscillator in motion, and the second cavity causes the oscillator to amplify the signal. The noise caused by amplification is restricted to the zero-point motion of the drum.

The theoretical system proposal has been published in Physical Review Letters.