Quantum noise

Although direct coupling of a camera to a scintillator can give acceptable results one of its major drawback is the degradation of the quantum noise mainly related to the low transmission of the optics. The following schematics summarizes the particles flux (photons and electrons) across the different stages of the detector ... 

Due to the conversion process an absorbed photon give rise to less than one electron generated in the CCD. This phenomenon, also called a "quantum sink" shows that the detector is degrading the S/N ratio of the image. The quality of an image being mainly limited by the quantum noise of the absorbed gamma this effect is very important. 

Carmichael, H.J. An Open Systems Approach to Quantum Optics Quantum Noise. Springer, 1993 Gardiner, C.W. and P. Zoller. Quantum Noise. Springer, 2000 Orszag, M. Quantum Noise, Springer, 2000. 

The desireable characteristics are high absolute densities and atomic numbers from about 55-65 to reduce quantum noise. 

R. Tanas, Quantum noise in nonlinear optical phenomena, first chapter in Part 1 of this three-volume set. 

C.W. Gardiner, Quantum Noise (Springer, Berlin 1991) and literature quoted there. 

It was found earlier that a sudden frequency change during an electronic Franck-Condon transition leads to special quantum mechanical statistics, called squeezing [2-9], of the molecular vibrations [10-12], A state is termed squeezed if some of its characteristics have less noise than the corresponding quantum noise of the vacuum state. The concept of squeezing turned out to be very fruitful in basic research and implies a lot of promising practical possibilities. 

W. Belzig, in Quantum Noise in Mesoscopic Physics, ed. by Yu.V. Nazarov, NATO Science Series 97, 463 (2003). 

Quantum Noise in Mesoscopic Physics, eds. Y. V. Nazarov, vol. 97 of NATO Science Series, Kluwer Academic Publishers, Dordrecht, the Netherlands, 2003. 

I had at this time moved back to the Karolinska Institute and started my own laboratory with a new Spectra Physics Model 164 Ar-ion laser which only exhibited quantum noise as compared to the heavy intensity fluctuation of the Argon laser in Gottingen which overshadowed our fluctuation spectra. 

If we choose to represent the environment in terms of quantum noise sources, the Ito interpretation [Gardiner 1991] allows us to write the relations... 

In plain English, we must predict the outcomes A2 and B2 with a precision better than the statistical spreading of the outcomes A and B with the additional constraint that A and l> are outcomes of quantum noise limited measurements. 

Gardiner C. W., Quantum Noise, (Springer-Verlag, Berlin 1991). 

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... 

Therefore, whenever the normal form of the quadrature variance is negative, this component of the field is squeezed or, in other words, the quantum noise in this component is reduced below the vacuum level. For classical fields, there is no unity coming from the boson commutation relation, and the normal form of the quadrature component represents true variance of the classical stochastic variable, which must be positive. 

Assuming that the quantum noise is small in comparison to the mean values of the field amplitudes, one can introduce the operators... 

On neglecting the quantum noise terms, l/ ao 2, one can easily recognize in (97) the first terms of the power series expansions of sech r and tanh r, which are the classical solutions. When oto 2 3> 1, the quantum noise introduces only small corrections to the classical evolution of the field amplitudes. It is also seen that the phase of the second harmonic field is phase-locked so as to satisfy ti = 2[Pg.28]

We can thus expect from the short-time approximation that quantum noise does not significantly affect the classical solutions when the initial pump field is strong. We will return to this point later on, but now let us try to find the short-time solutions for the evolution of the quantum noise itself—let us take a look at the quadrature noise variances and the photon statistics. Using the operator solutions (94) and (95), one can find the solutions for the quadrature operators Q and P as well as for Q2 and P2. It is, however, more convenient to use the computer program to calculate the evolution of these quantities directly. Let us consider the purely SHG process, we drop the terms containing b and b+ after performing the normal ordering and take the expectation value in the coherent... 

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