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Operators given by ^ = (^ † + ^) and ^ = (^ † ^) are called the quadratures and they represent the real and imaginary parts of the complex amplitude represented by ^. [1] The commutation relation between the two quadratures can easily be calculated:
The two amplitude-modulated sinusoids are known as the in-phase (I) and quadrature (Q) components, which describes their relationships with the amplitude- and phase-modulated carrier. [ A ] [ 2 ] Or in other words, it is possible to create an arbitrarily phase-shifted sine wave, by mixing together two sine waves that are 90° out of phase in ...
It is assumed that the value of a function f defined on [,] is known at + equally spaced points: < < <.There are two classes of Newton–Cotes quadrature: they are called "closed" when = and =, i.e. they use the function values at the interval endpoints, and "open" when > and <, i.e. they do not use the function values at the endpoints.
Quadrature amplitude modulation (QAM), a modulation method of using both an (in-phase) carrier wave and a 'quadrature' carrier wave that is 90° out of phase with the main, or in-phase, carrier Quadrature phase-shift keying (QPSK), a phase-shift keying of using four quadrate points on the constellation diagram, equispaced around a circle
The measured electric field strengths at the wave's phase are the eigenvalues of the normalized quadrature operator , defined as [5] ^ = [^ + ^ †] = ^ + ^ where ^ and ^ † are the annihilation and creation operators, respectively, of the oscillator representing the photon.
The term squeezed state is actually used for states with a standard deviation below that of the ground state for one of the operators or for a linear combination of the two. The idea behind this is that the circle denoting the uncertainty of a coherent state in the quadrature phase space (see right) has been "squeezed" to an ellipse of the same ...
In the quantum mechanics study of optical phase space, the displacement operator for one mode is the shift operator in quantum optics, ^ = (^ † ^), where is the amount of displacement in optical phase space, is the complex conjugate of that displacement, and ^ and ^ † are the lowering and raising operators, respectively.
The term numerical quadrature (often abbreviated to quadrature) is more or less a synonym for "numerical integration", especially as applied to one-dimensional integrals. Some authors refer to numerical integration over more than one dimension as cubature ; [ 1 ] others take "quadrature" to include higher-dimensional integration.