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Researchers Store Optical Data In Five Dimensions
Al writes "Researchers from Swinburne University of Technology in Victoria, Australia, have developed an optical material capable of storing information in five dimensions. Using three wavelengths and two polarizations of light, the Australian researchers were able to write six different patterns within the same area. The material is made up of layers of gold nanorods suspended in clear plastic that has been spun flat onto a glass substrate and multiple data patterns can be written and read within the same area in the material without interference. The team achieved a storage density of 1.1 terabytes per cubic centimeter by writing data to stacks of 10 nanorod layers."
Your example is easy to relate to, but there's a problem people should be aware of. While you can refer to the book's location using a 6-dimensional quantity, you *could* do it in 3, by giving its position in space. In a "real" n-dimensional system, you cannot reduce the system to less than n dimensions.
A good, but less-accessible example, is the state of an object in classical mechanics. The position of an object is 3-dimensional. The state, however, is 6-dimensional: your position (3D) and momentum (3D).
Hmm... why are they calling it 5? Am I missing something?
Yes - the dimension of the system is just the number of independent variables, the 3 wavelengths and the 2 polorisations.
Think about it in terms of a 1D line vs a 2D plane. In the case of the line there is the less than 0 and greater than 0 regions. When you move up to a plane there are two new greater than 0 and less than 0s (in the y plane as opposed to the x plane of the 1D line, say). So you have 4 possible combinations (or quadrants in the plane) in 2 dimensions.
Also - note that light which is circularly polarised is both vertically polarised *and* horizontally polarised, so you can have unpolarised red light; vertically polarised red light; horizontally polarised red light and vertically and horizontally polarised red light.
(Similar to: just red light; red light and blue light; red light and green light and red light blue light and green light)