Mis optical memory with phase-sensitive readout

L. A. Nefedev

Aleksei M. Zheltikov

The signal-to-noise contrast of the optical readout in broadband Raman quantum memories is analyzed as a function of the pulse widths and phase properties of tailored optical field waveforms used to write in and read out broadband photon wave packets. Based on this analysis, we quantify the tradeoff between the readout contrast and the speed of such memories. Off-resonance coherent four-wave mixing is shown to provide a source of noise photons, lowering the readout contrast in broadband Raman quantum memories. This noise cannot be suppressed by phase matching, but can be radically reduced with a suitable polarization arrangement and proper field-waveform tailoring.

James Vinton Burt

Takuya Kawasaki, Sotatsu Otabe, Tomoya Sato +3 more

The sensitivity of an interferometer depends on its readout scheme. However, little attention has been paid to the readout schemes of atom interferometers from the viewpoint of their sensitivity. The difference in sensitivity between readout schemes or their optimization has not been considered in the literature. Herein we analytically calculate the sensitivities of an atom interferometer with typical readout schemes by applying the two-photon formalism, which was developed for optical interferometers to deal with quantum noise. Our calculations reveal that by using sinusoidal phase modulation, the sensitivity can surpass that obtained by the conventional phase sweeping scheme. The superiority of this phase modulation scheme for both cold and thermal atomic beams is demonstrated. In addition, we show that the phase modulation scheme is advantageous for atom-flux fluctuation and resists atom-flux drift. This study performs a general analysis of the sensitivity of atom interferometers and identifies an advantageous readout scheme.

Rachel Pei Chin Won

Ju-Seog Jang, Dong-Hak Shin

We explain that it is possible in principle to detect a change in light transmittance and phase shift of transparent materials without exposing even a single photon on them. Based on such interaction-free measurement, novel rewritable optical memories can be constructed with a photo-sensitive medium. In this case, even if the stored data are vulnerable to light, they can be read out without (or, at least a reduced) data impairment, because there is no (or, at least a reduced) interaction between the photon and the medium. We also discuss the effect of two system imperfections, the system loss and the low quantum efficiency of photon detectors, when such memories are to be implemented.