Non-destructive, dynamic detectors for Bose-Einstein condensates

TL;DR

This paper introduces non-destructive, real-time detectors for Bose-Einstein condensates using shot noise limited photodetectors, comparing various schemes and proposing cavity-based measurements for minimal disturbance.

Contribution

It analyzes and compares different non-destructive detection schemes for BECs, highlighting the advantages of cavity-based measurements for minimal disturbance.

Findings

Interferometry causes as much destruction as absorption in optically thin clouds.

Cavity-free interferometry is better than absorption for optically thick clouds.

Cavity-based measurements can be arbitrarily non-destructive for a given SNR.

Abstract

We propose and analyze a series of non-destructive, dynamic detectors for Bose-Einstein condensates based on photo-detectors operating at the shot noise limit. These detectors are compatible with real time feedback to the condensate. The signal to noise ratio of different detection schemes are compared subject to the constraint of minimal heating due to photon absorption and spontaneous emission. This constraint leads to different optimal operating points for interference-based schemes. We find the somewhat counter-intuitive result that without the presence of a cavity, interferometry causes as much destruction as absorption for optically thin clouds. For optically thick clouds, cavity-free interferometry is superior to absorption, but it still cannot be made arbitrarily non-destructive . We propose a cavity-based measurement of atomic density which can in principle be made arbitrarily non-destructive for a given signal to noise ratio.