Engineering micromechanical quantum correlations for sensitive measurements

Aalto Quantum Physics Seminar (Nanotalo). Speaker: Prof. Mika Sillanpää (NEMS, Aalto University, Finland).

This talk is covering the work carried out in the CQE project Quantum-enhanced measurements and metrology (QMETRO). I will focus on work on quantum electromechanical devices done in the NEMS group. In the first part of the talk, I will discuss mechanical microwave amplifiers. We demonstrate a sub-quantum limited phase-sensitive microwave amplifier made with a microwave electromechanical scheme, characterized by an extremely small noise less than 0.2 quanta. I will describe progress towards realizing the scheme at 3 Kelvin temperature. In the second part of the talk, I will discuss how quantum backaction in the electromechanical device can be used to squeeze propagating microwaves. Quantum squeezing is an important tool to reduce noise in sensitive measurements. Under a strong measurement, the shot noise of incoming microwaves becomes imprinted to the motion of the mechanical oscillator, which in turn feeds back to the incoming signal. Here we observe such "ponderomotive" squeezing in the microwave domain. However, a homodyne measurement that is usually used to reveal squeezing can be blind to some kinds of squeezing correlations. We use a modified type of phase-sensitive measurement employing two local oscillators to detect the hidden quantum correlations.