Themes in Howard Wiseman's Physics Research

Themes in Howard Wiseman's Research in Physics

Quantum Information and Entanglement

This is a major research area in the Centre for Quantum Computer Technology. I am interested in how super-selection rules (dynamical constraints) impact upon quantum information processing. I am also interested in entanglement issues, in particular how the Einstein-Podolsky-Rosen paradox from 1935 can be formalized, and how it can be tested experimentally in novel ways that may apply to more secure communication in quantum cryptography.

Dynamics of Open Quantum Systems

My interest here is primarily in quantum optical systems which obey (approximately) a master equation, although I have also done a lot of work on non-Markovian quantum systems. One of the fascinating aspects of open quantum systems is how the system dynamics can be qualitatively altered by altering the way in which the environment is monitored, without changing the master equation. This sets up a tension with the popular idea that somehow the environment of open quantum systems forces them to behave in a unique, pseudo-classical way. Current work is proceeding in investigating this tension.

Quantum Feedback

One sort of open quantum system which is that in which the results of monitoring the environment are used to alter the system dynamics. This quantum feedback can lead to interesting changes in the global system dynamics and more subtle changes in the quantum fluctuations. It has also contributed to ideas in quantum error correction for quantum computing and also for protection of Schroedinger cat states. The use of non-Markovian feedback, in particular State-based feedback, is an active topics of investigation.

Adaptive Quantum Measurements

In text books of quantum mechanics measurements are usually treated quite formally, and one finds statements such as "all Hermitian operators represent an observable". Little space is devoted to how general physical quantities could be observed in a laboratory. In the quantum optics context, it is obvious how to measure some observables. For example, photon number can be measured using a photodetector. Other observables, such as phase, cannot be measured in any simple way. To attempt to measure phase one needs complicated techniques such as adaptive measurements. This is an area of active collaboration with experimental groups.

Fundamental Issues in Quantum Mechanics

I have interests in the "quantum measurement problem" and the philosophy of quantum mechanics. One specific issue is whether the uncertainty relation has anything to say about the destruction of interference in which-path measurements. A number of ways of answering this question have been investigated, including using Bohmian mechanics. I am interested in this, and other interpretations especially in how they treat probabilities and time. I am agnostic as to the best interpretation of quantum mechanics. More recently, I have become interested in weak values, how they can be applied to which-way experiments, and what they may have to say about the interpretation of quantum mechanics.

Return to Howard Wiseman's Home Page