Minimal absorption measurements - art. no. 062303

In this paper, we consider the problem of trying to make an image of an obj ect while minimizing the number of photons absorbed by the object. We call protocols that achieve this goal "minimal absorption measurements." Such im aging techniques are particularly relevant in situations where the ob ect m a be damaged by the radiation used to make the image, Our main result is a bound that relates the minimum number of absorbed photons to the sensitivit y of the measurement. This bound holds where epsilon, half the difference b etween the transparencies, is sufficently small. In the case where the obje ct consists of a single pixel, we show that the dependency of our bound on epsilon may be reproduced by simply counting the number of photons absorbed by the object or by a simple interferometric setup. depending on the detai ls of the problem. In the case where the object consists of many pixels, we give an example where our bound may be approached when all the pixels are addressed collectively. whereas addressing each pixel individually implies an increase in the number of absorbed photons by a factor logarithmic in th e number of pixels. Finally, we consider some special situations,A here our bound does not apply. and where interferometric methods may make large gai ns.