Heisenberg uncertainty quantum optics

The Heisenberg uncertainty relation (9) imposes basic restrictions on the accuracy of the simultaneous measurement of the two quadrature components of the optical held. In the vacuum state the noise is isotropic and the two components have the same level of quantum noise. However, quantum states can be produced in which the isotropy of quantum fluctuations is broken—the uncertainty of one quadrature component, say, Q, can be reduced at the expense of expanding the uncertainty of the conjugate component, P. Such states are called squeezed states [5,6]. They may or may not be the minimum uncertainty states. Thus, for squeezed states... 

There are technical causes characteristic to the instrument and collectively known as instrumental parameters width of entrance slit, quality of the optics, focal distance, diffraction phenomena through narrow orifices. However, there are also causes due to quantum mechanics, which ensure that the spectral transitions have a natural width . The radiations emitted by the atoms are not quite monochromatic. In particular with the plasmas, a medium in which the collision frequency is high (this reduces enormously the lifetimes of the excited states), Heisenberg s uncertainty principle plays a large role (Figure 14.7). Moreover, the elevated temperatures increase the speed of the atoms, enlarging line widths by the Doppler effect. Finally for all of these reasons, the width of the lines at 6000 K reaches several picometres. 

Thus, for even the very best possible high-gain amplifier with complete inversion (Usp = 1), the noise figure F is never less than 2 (3.01 dB). This is a fundamental result for an IMDD system that can be arrived at more generally using Heisenberg s uncertainty principle as the starting point. While this so-called quantum limit has been approached in other types of optical amplifier (most notably erbium-doped fiber amplifiers), it is never achieved in SOAs because, as Fig. 9 shows, the spontaneous emission factor never reaches the theoretical limit of Usp =. ... 

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