Quadratic coupling between a classical nanomechanical oscillator and a single spin

Dhingra, Shonali (2015) Quadratic coupling between a classical nanomechanical oscillator and a single spin. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

Though the motions of macroscopic objects must ultimately be governed by quantum mechanics, the distinctive features of quantum mechanics can be hidden or washed out by thermal excitations and coupling to the environment. For the work of this thesis, we tried to develop a hybrid system consisting a classical and a quantum component, which can be used to probe the quantum nature of both these components. This hybrid system quadratically coupled a nanomechanical oscillator (NMO) with a single spin in presence of a uniform external magnetic field.

The NMO was fabricated out of single-layer graphene, grown using Chemical Vapor Deposition (CVD) and patterned using various lithography and etching techniques. The NMO was driven electrically and detected optically. The NMO's resonant frequencies, and their stabilities were studied.

The spin originated from a nitrogen vacancy (NV) center in a diamond nanocrystal which is positioned on the NMO. In presence of an external magnetic field, we show that the NV centers are excellent $\theta^{2}$ sensors. Their sensitivity is shown to increase much faster than linearly with the external magnetic field and diverges as the external field approaches an internally-defined limit.

Both these components of the hybrid system get coupled by physical placement of NV-containing diamond nanocrystals on top of NMO undergoing torsional mode of oscillation, in presence of an external magnetic field. The capability of the NV centers to detect the quadratic behavior of the oscillation angle of the NMO with excellent sensitivity, ensures quantum non-demolition (QND) measurement of both components of the hybrid system. This enables a bridge between the quantum and classical worlds for a simple readout of the NV center spin and observation of the discrete states of the NMO. This system could become the building block for a wide range of quantum nanomechanical devices.

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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
Dhingra, Shonalishd28@pitt.eduSHD28
ETD Committee:
Committee ChairD'Urso, Briandursobr@pitt.eduDURSOBR
Committee MemberDutt, Gurudevgdutt@pitt.eduGDUTT
Committee MemberDaley, Andrewandrew.daley@strath.ac.uk
Committee MemberCole, Danieldgcole@pitt.eduDGCOLE
Date: 18 June 2015
Date Type: Publication
Defense Date: 13 April 2015
Approval Date: 18 June 2015
Submission Date: 19 March 2015
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 183
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Graphene, NV centers, Nanomechanical oscillator, Spin system, Hybrid system
Date Deposited: 18 Jun 2015 15:00