OBSERVABLE FREQUENCY-SHIFTS VIA SPIN-ROTATION COUPLING

The phase perturbation arising from spin-rotation coupling is develope d as a natural extension of the celebrated Sagnac effect. Experimental evidence in support of this phase shift, however, has yet to be reali zed due to the exceptional sensitivity required. We draw attention to the relevance of a series of experiments establishing that circularly polarized light, upon passing through a rotating half-wave plate, is c hanged in frequency by twice the rotation rate. These experiments may be interpreted as demonstrating the role of spin-rotation coupling in inducing this frequency shift, thus providing direct empirical verific ation of the coupling of the photon helicity to rotation. A neutron in terferometry experiment is proposed which would be sensitive to an ana logous frequency shift for fermions. In this arrangement, polarized ne utrons enter an interferometer containing two spin flippers, one of wh ich is rotating while the other is held stationary. An observable beat ing in the transmitted neutron beam intensity is predicted. (C) 1998 P ublished by Elsevier Science B.V.