Quantum metrology

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Quantum metrology is the study of making high resolution measurements of parameters using quantum theory to describe the physical systems. This can give rise to measurements which give better precision than the same measurement performed in a classical framework. One example of note is the use of the so-called NOON state in a Mach-Zender interferometer to perform accurate phase measurements. A similar effect can be produced using less exotic states such as squeezed states.

One application of particular note is the detection of gravitational radiation. Here high precision distance measurements must be made of two widely separated masses. However, currently the measurements described by quantum metrology are usually not used as they are very difficult to implement and there are many other sources of noise which prohibit the detection of gravity waves which must be overcome first.