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Coupled dynamics of a nanomechanical resonator and superconducting quantum circuits

Citation

Suh, Junho (2011) Coupled dynamics of a nanomechanical resonator and superconducting quantum circuits. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:04122011-090427340

Abstract

The coupled dynamics of a nanomechanical resonator and superconducting quantum circuits are studied in three experiments, in the context of studying the quantum limit for force detection and quantum physics of macroscopic objects. In the first experiment, the dispersive mechanical resonance shift from the interaction with a Cooper-pair box qubit is studied. The measured coupling strength is large enough to satisfy one of the conditions required to perform many of the proposed quantum nanomechanical measurements. The resonance shift also probes the microwave-driven response of the qubit, showing Rabi oscillation and Landau-Zener tunneling, proving the coherent dynamics of the qubit. Second, the parametric excitation of nanomechanical motion is studied via experiments with a driven qubit. Degenerate parametric amplification and oscillation are demonstrated, with a new observation of nonlinear dissipation. The squeezing of the back-action noise from the detection amplifier is also observed, up to 4dB. It is the first demonstration using a qubit as an auxiliary system to modify the nanomechanical dynamics, showing a possible route for generation of nanomechanical quantum states. Finally, back-action cooling of nanomechanical motion has been investigated, which is implemented by capacitively coupling a high-Q coplanar waveguide microwave resonator to a nanomechanical resonator. The thermal state with 7.5 mechanical quanta on average is reached, a result that is ultimately limited due to increased bath heating with microwave power. The heating is consistent with a model based on two-level systems resonantly coupled to the nanomechanical mode. This additional heating suggests future efforts to improve coupling and for reducing two-level system density in materials employed to reach the motional ground state via back-action cooling.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:nanoelectromechanical system, qubit, quantum measurement, parametric amplification, superconducting microwave resonator
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Roukes, Michael Lee
Thesis Committee:
  • Schwab, Keith C.
  • Vahala, Kerry J.
  • Chen, Yanbei
Defense Date:9 March 2011
Record Number:CaltechTHESIS:04122011-090427340
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:04122011-090427340
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6310
Collection:CaltechTHESIS
Deposited By: Junho Suh
Deposited On:18 May 2011 17:02
Last Modified:26 Dec 2012 04:34

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