2025/01/19 by Prasanta Kumbhakar, Anusha Shanmugam, Kumbhakar, Prasanta +11
Physics and Astronomy · #FOS: Physical sciences #Force Microscopy Techniques and Applications #Mechanical and Optical Resonators #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Semiconductor Quantum Structures and Devices
paper · pdf · doi:10.48550/arxiv.2501.11056
openalex publication_date 2025/01/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Inherent randomness and the resulting stochastic behavior of fundamental particles manifested as quantum noise put a lower bound on measurement imprecision in the quantum measurement process. In addition, the quantum noise imparts decoherence and dephasing to the system being measured, referred to as the measurement back-action. While the microscopic effects of back-action have been observed, macroscopic evidence is a rarity. Here we report a macroscopic display of the back-action of an ultra-sensitive quantum point contact (QPC) electrical amplifier whose transport is defined by the quantum tunneling of electrons. The QPC amplifier, realized on GaAs-AlGaAs heterostructures, coupled to a planar superconducting resonator, operates at a frequency of 2.155 GHz in the shot-noise-limited regime. The shot-noise excitation of the mechanical modes and the resulting piezoelectric polarization enhancing the shot-noise at the mode frequencies form a positive feedback loop between the electrical and mechanical degrees of freedom. While the excitation of the vibrational modes is a display of the macroscopic effects of measurement back-action, the amplitudes of the noise peaks allow us to calibrate the displacement sensitivity of the QPC-resonator systems, which is in the order of 35 fm/SQRT(Hz) range, making it an excellent sensor for ultra-sensitive and fast strain or displacement detection.