Quantum Metrology
We are looking for a post-graduate student to join the newly formed quantum
information theory group of Animesh Datta at the University of Warwick. The goals
of this theoretical project are first, to better understand the fundamental limits to
precisions attainable in measurements, and second, to propose new techniques that
use quantum physics to provide enhanced precisions. The student should be
interested in a close interplay between concepts from theoretical quantum physics
and techniques from mathematics. A willingness to engage in discussions with
experimentalists at Warwick and elsewhere would also be essential.
Background: A striking consequence of quantum theory is that fundamental limits
on the information gained by a quantum-mechanical measurement apparatus can
exceed that possible with a classical instrument. The field of quantum metrology
seeks to identify situations in which such advantages can arise, the essential
quantum resources required of the apparatus, and the approaches with which
quantum-enhanced measurements can be realized in the laboratory. Despite continuing improvements in the experimental control of quantum systems,
practical quantum metrology is limited due to the inherent sensitivity of quantum
probes to undesired environmental disturbances. In this project, we seek to clarify
theoretically the required resources for quantum-enhanced metrology and devise
new strategies for quantum measurements that are robust against imperfections
such as dephasing and loss [1].
Project: The project will involve deriving the form of optimal quantum states for
estimating multiple parameters such as phase, loss, and dephasing using
techniques from probability and estimation theory. We will investigate both
continuous-variable states such as single and multi-mode squeezed states, as well
as fixed-photon-number states such as Holland-Burnett states as quantum probes
for problems such as multimode phase imaging [2].
We will also study optimal detection strategies for these scenarios, investigating
both number-resolved and homodyne detection as well as photon-counting
measurements. More generally, we will seek to understand the role of both probes
and detection methods that are Gaussian and non-Gaussian in nature. In practical
terms, this project looks to eventually develop precise imaging methods that are
applicable to outstanding problems in the biological and medical sciences. At the
same time, we seek to better understand the essential limits of measurement – a
truly fundamental aspect of science in the light of quantum information theory. The
techniques learnt can and will be applied to fundamental problems in quantum
information theory such the role of non-classical correlations in quantum
enhancements in information processing.
[1]
Datta, Zhang, Thomas-Peter, Dorner, Smith, and Walmsley, Physical Review
A 83, 063836 (2011).
[2]
Humphreys, Barbieri, Datta, and Walmsley, Physical Review Letters 111,
070403 (2013).