Alexandria Digital Research Library

Preserving entanglement during weak measurement demonstrated with a violation of the Bell-Leggett-Garg inequality

Author:
White, Theodore C.
Degree Grantor:
University of California, Santa Barbara. Physics
Degree Supervisor:
John M. Martinis
Place of Publication:
[Santa Barbara, Calif.]
Publisher:
University of California, Santa Barbara
Creation Date:
2015
Issued Date:
2015
Topics:
Quantum physics
Keywords:
Quantum
Condensed Matter
Amplifiers
Superconductivity
Genres:
Dissertations, Academic and Online resources
Dissertation:
Ph.D.--University of California, Santa Barbara, 2015
Description:

Quantum mechanics makes many predictions, such as superposition, projective measurement, and entanglement, which defy classical intuition. For many years it remained unclear if these predictions were real physical phenomena, or the result of an incomplete understanding of hidden classical variables. For quantum entanglement, the Bell inequality provided the first experimental bound on such hidden variable theories by considering correlated measurements between spatially separated photons. Following a similar logic, the Leggett-Garg inequality provides an experimental test of projective measurement by correlating sequential measurements of the same object. More recently, these inequalities have become important benchmarks for the "quantumness'' of novel systems, measurement techniques, or methods of generating entanglement. In this work we describe a continuous and controlled exchange of extracted state information and two-qubit entanglement collapse, demonstrated using the hybrid Bell-Leggett-Garg inequality. This effect is quantified by correlating weak measurement results with subsequent projective readout to collect all the statistics of a Bell inequality experiment in a single quantum circuit. This result was made possible by technological advances in superconducting quantum processors which allow precise control and measurement in multi-qubit systems. Additionally we discuss the central role of superconducting Josephson parametric amplifiers, which are a requirement for high fidelity single shot qubit readout. We demonstrate the ability to measure average Bell state information with minimal entanglement collapse, by violating this hybrid Bell-Leggett-Garg inequality at the weakest measurement strengths. This result indicates that it is possible to learn about the dynamics of large entangled systems without significantly affecting their evolution.

Physical Description:
1 online resource (178 pages)
Format:
Text
Collection(s):
UCSB electronic theses and dissertations
ARK:
ark:/48907/f30g3hbf
ISBN:
9781339219271
Catalog System Number:
990045866220203776
Rights:
Inc.icon only.dark In Copyright
Copyright Holder:
Theodore White
File Description
Access: Public access
White_ucsb_0035D_12781.pdf pdf (Portable Document Format)