The Doppler Effect in Sound Waves, Light Waves, and Quantum Waves

E G Lariontsev

We report a theoretical study of transformation of a biphoton state of light under Bragg diffraction on a travelling sound wave in an acousto-optic modulator (AOM). It is shown that the diffraction of AOM biphotons emitted during the collinear parametric scattering of light leads to a shift of the carrier frequency of a biphoton wave packet, which exceeds twice the Doppler frequency shift for the classical field. A method is proposed for measuring the Doppler frequency shift of a biphoton, which is based on interference between independent biphotons.

G. S. Ranganath

Daniel Hodgson, Sara Kanzi, Almut Beige

The relativistic Doppler effect comes from the fact that observers in different inertial reference frames experience space and time differently, while the speed of light always remains the same. Consequently, a wave packet of light exhibits different frequencies, wavelengths, and amplitudes. In this paper, we present a local approach to the relativistic Doppler effect based on relativity, spatial and time translational symmetries, and energy conservation. Afterwards, we investigate the implications of the relativistic Doppler effect for the quantum state transformations of wave packets of light and show that a local photon is a local photon at the same point in the spacetime diagram in all inertial frames.

Eymen Güler

A Kumar, N Anderson, William D. Phillips +3 more

The Doppler effect, the shift in the frequency of sound due to motion, is present in both classical gases and quantum superfluids. Here, we perform an in situ , minimally destructive measurement, of the persistent current in a ring-shaped, superfluid Bose–Einstein condensate using the Doppler effect. Phonon modes generated in this condensate have their frequencies Doppler shifted by a persistent current. This frequency shift will cause a standing-wave phonon mode to be 'dragged' along with the persistent current. By measuring this precession, one can extract the background flow velocity. This technique will find utility in experiments where the winding number is important, such as in emerging 'atomtronic' devices.

Bernard Cagnac