Ramsey fringe technique

This value agrees with the astronomical definition based on the tropical year of 1900 within the accuracy of the latter definition. The stability and reproducibility are presently about 1 10. The Ramsey-fringe technique is used to attain this high degree of accuracy. 

Future possibilities for accurate H spectroscopy have been discussed in [9.208,209]. The optical analogy to the Ramsey-fringe technique (Sect. 7.1.2) has been demonstrated for the case of two-photon absorption. In Fig.9.51 the inevitable Fourier broadening of a short pulse is illustrated. 

Fig.9.51. Illustration of the optical Ramsey fringe technique in the time domain [9.210]...

A term that is nearly synonymous with complex numbers or functions is their phase. The rising preoccupation with the wave function phase in the last few decades is beyond doubt, to the extent that the importance of phases has of late become comparable to that of the moduli. (We use Dirac s terminology [7], which writes a wave function by a set of coefficients, the amplitudes, each expressible in terms of its absolute value, its modulus, and its phase. ) There is a related growth of literature on interference effects, associated with Aharonov-Bohm and Berry phases [8-14]. In parallel, one has witnessed in recent years a trend to construct selectively and to manipulate wave functions. The necessary techniques to achieve these are also anchored in the phases of the wave function components. This trend is manifest in such diverse areas as coherent or squeezed states [15,16], electron transport in mesoscopic systems [17], sculpting of Rydberg-atom wavepackets [18,19], repeated and nondemolition quantum measurements [20], wavepacket collapse [21], and quantum computations [22,23]. Experimentally, the determination of phases frequently utilizes measurement of Ramsey fringes [24] or similar methods [25],... 

Some techniques of laser spectroscopy, such as the method of separated fields optical Ramsey fringes. Sect. 9.4), coherent transient spectroscopy (Sect. 7.6), or polarization spectroscopy (Sect. 2.4) allow one to distinguish between phasechanging, velocity-changing, or orientation-changing collisions. 

Fortunately, several methods have been developed that overcome these difficulties and that allow ultranarrow Ramsey resonances to be obtained. One of these methods is based on Doppler-free two-photon spectroscopy, while another technique uses saturation spectroscopy but introduces a third interaction zone at the distance z = 2L downstream from the first zone to recover the Ramsey fringes [1257-1259]. We briefly discuss both methods. 

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