Better off together: Improved quantum estimation of multiple parameters
Numerous scenarios in science and technology require the estimation of vectors such as electric, magnetic, gravitational or other force fields with extreme precision, the fundamental limits to which are set by quantum mechanics. In their latest paper, Tillmann Baumgratz and Animesh Datta show that quantum mechanics allows a more precise estimation of multiple parameters simultaneously rather than individually. the result provides a fundamentally better way estimating vector fields for a fixed amount of resources, and could be used in applications ranging from the study of quantum phase transitions to neuroimaging.
The advantage in estimating several parameters simultaneously is a uniquely quantum property that is impossible classically. The probes discovered therefore possess uniquely quantum properties such as quantum entanglement. This work is the first to demonstrate a novel form of quantum parallelism that can be exploited to extract more advantages than ever thought before [see the figure below for the 3 different scenarios]. Incidentally, the work also shows that while quantum entanglement is useful, too much quantum entanglement is bad for precise estimation.
While challenging, the experimental work to construct the novel quantum probes proposed should be possible in laboratories across the world in the coming years.
For more information, see http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.030801