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Precision tests of QED have been performed in low-energy atomic physics experiments, high-energy collider experiments, and condensed matter systems. The value of α is obtained in each of these experiments by fitting an experimental measurement to a theoretical expression (including higher-order radiative corrections) that includes α as a parameter.
The precision of a measurement system, related to reproducibility and repeatability, is the degree to which repeated measurements under unchanged conditions show the same results. [ 3 ] [ 4 ] Although the two words precision and accuracy can be synonymous in colloquial use, they are deliberately contrasted in the context of the scientific method .
An important application of particular note is the detection of gravitational radiation in projects such as LIGO or the Virgo interferometer, where high-precision measurements must be made for the relative distance between two widely separated masses. However, the measurements described by quantum metrology are currently not used in this ...
Quantum metrology is the use of quantum physics to aid the measurement of quantities that, generally, had meaning in classical physics, such as exploiting quantum effects to increase the precision with which a length can be measured. [52]
A quantum limit in physics is a limit on measurement accuracy at quantum scales. [1] Depending on the context, the limit may be absolute (such as the Heisenberg limit), or it may only apply when the experiment is conducted with naturally occurring quantum states (e.g. the standard quantum limit in interferometry) and can be circumvented with advanced state preparation and measurement schemes.
The precision of the position is improved, i.e. reduced σ x, by using many plane waves, thereby weakening the precision of the momentum, i.e. increased σ p. Another way of stating this is that σ x and σ p have an inverse relationship or are at least bounded from below. This is the uncertainty principle, the exact limit of which is the ...
The 2004 best estimate of sin 2 θ w, at ∆q = 91.2 GeV/c, in the MS scheme is 0.231 20 ± 0.000 15, which is an average over measurements made in different processes, at different detectors. Atomic parity violation experiments yield values for sin 2 θ w at smaller values of ∆ q , below 0.01 GeV/ c , but with much lower precision.
Metrology is a wide reaching field, but can be summarized through three basic activities: the definition of internationally accepted units of measurement, the realisation of these units of measurement in practice, and the application of chains of traceability (linking measurements to reference standards).