Quantum physics has come a long way since its theoretical beginnings in the early twentieth century. Techniques to manipulate light and matter have become increasingly sophisticated, facilitating fundamental studies of quantum effects and inspiring new technologies. From atomic networks to semiconductor 'spintronics', seemingly disparate areas of research are being driven by a shared goal — to harness and exploit quantum coherence and entanglement.
Inevitably, these laboratory endeavours have necessitated a new theoretical toolbox. The image of a pair of photons zooming off in opposite directions, each sensitive to the other through their quantum entanglement, is conceptually tidy. But what happens when describing the quantum properties of more complex systems? This Insight on quantum coherence and entanglement starts with a Progress article that addresses the problem of 'thinking big': how can entanglement be quantified or measured in a system that comprises many particles and degrees of freedom?
The reviews in this Insight highlight the exciting experimental progress in such systems, covering a wide range of physical settings. They describe both bottom-up approaches, in which researchers strive to achieve increasingly complex systems starting from a very small number of particles and degrees of freedom, and top-down approaches, in which the individual and collective degrees of freedom in larger systems are controlled. Ultimately, the goal is to control many-particle systems at the quantum limit, an attractive prospect for quantum simulation and information applications.
As such, this Insight brings together varied research. We trust, however, that you will find coherence in this diversity.
Rights and permissions
About this article
Cite this article
Southwell, K. Quantum coherence. Nature 453, 1003 (2008). https://doi.org/10.1038/4531003a
This article is cited by
Quantitative wave–particle duality relations from the density matrix properties
Quantum Information Processing (2020)
Quantifying Quantum-Mechanical Processes
Scientific Reports (2017)
Observing coherence effects in an overdamped quantum system
Nature Communications (2016)
Testing the limits of quantum mechanical superpositions
Nature Physics (2014)
Dynamic and steady control of quantum coherence in photonic crystals via the Zeeman effect
Science China Physics, Mechanics and Astronomy (2012)