Integrating low-loss massive mechanical resonators with single-electron devices

Jorge Tiago Santos

Research output: ThesisDoctoral ThesisCollection of Articles


Since the development of quantum mechanics, there has been debate over the extent to which it can be applied to macro-world objects. The motion of a macroscopic body is one of the most intriguing physical quantities to experimentally investigate in the quantum regime. Experiments on macroscopic mechanical resonators in the quantum ground state are motivated not only by accessing and testing new regimes of quantum mechanics. Detection of the quantum motion requires extremely sensitive displacement sensing techniques, having relevance in other fields of research or engineering. Mechanical quantum devices are also promising in the field of quantum engineering, where ultralow energy losses achievable in mechanical resonators can become an indispensable resource. In this thesis, I experimentally explore new types of detection methods for mechanical resonators near the quantum regime, as well as investigate energy dissipation mechanism in such devices. I study two types of promising systems: monolithic quartz crystal resonators, and nanocrystalline diamond resonators. Monolithic quartz resonators are inexpensive, resilient and can exhibit low energy losses and high quality factors up to 10 exp 9. They are millimetre-sized with masses in the milligram range and resonance frequencies of some MHz, and can be brought into a regime not too far from the quantum limit with standard cryogenic technology. The piezoelectric charge in quartz offers a transduction option to measure the mechanical vibrations using charge detectors. I experimentally investigate the possibility of measuring their ground state vibrations using several different measurement typologies of single electron transistors that are the ultimate charge sensitive devices. In the most promising scheme, I show how the combined device can be treated as a cavity optomechanical scheme where a charge qubit mediates and enhances the interaction between the quartz mechanical oscillator and a microwave cavity. I investigate using optomechanical back-action cooling of the quartz resonator, showing results demonstrating modest cooling power. I investigate loss mechanisms of the quartz resonators, and show how electrical losses in the experimental setup can appear as a limiting factor for reaching high quality factors. I predict that the ground state can be reached by some realistic design of the piezoelectric dissipation, or coupling to the Qubit. In the non-superconducting state, although quantum limit is harder to achieve, I demonstrate how single-electron devices are usable as highly sensitive motion detectors of the quartz. Besides quartz, in this thesis I suggest the use of nanocrystalline diamond resonators as an alternative mechanical system for studies in the quantum limit, and study its energy loss mechanisms.
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Sillanpää, Mika, Supervisor
  • Sillanpää, Mika, Advisor
Print ISBNs978-952-60-8050-5
Electronic ISBNs978-952-60-8051-2
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)


  • quantum ground state
  • macroscopic mechanical resonators
  • mechanical dissipation
  • cavity optomechanics
  • single electron devices
  • piezoelectric devices

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    Aalto University

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