Can we make precision measurements more precise

Jacob Dunningham

Progress in science is inextricably linked with how well we can observe the world around us. It is by making increasingly better measurements that scientific theories are tested and refined. In this article we address the question of what the ultimate limit to measurement precision is and how it could be achieved in the laboratory. We focus on how, by making use of quantum theory, it is possible to make better measurements than anything that can be achieved with classical techniques. This opens the door to an array of new technologies and could help answer some of science's most engaging questions.

J. M. Geremia

Taesoo Kim, Jacob Dunningham, Keith R. Burnett

We present a scheme that makes use of quantum mechanical entanglement to significantly enhance the measurement precision accessible by interferometers. This is achieved by making use of a special type of interferometer composed of two ``quantum beam splitters,'' which each transform the input particles into a macroscopic superposition at the outputs. We show that this technique not only enables phase measurements to be made with Heisenberg limited precision, but also overcomes the major practical problems of detector inefficiencies and imperfect beam splitters. It may provide a promising route to implementing sub-shot-noise limited measurement schemes in the laboratory.

Gianluca Rastelli, Ioan M. Pop

James C. Camparo

Across a broad range of disciplines, the accurate determination of an electromagnetic wave's amplitude (either absolute or relative) has considerable relevance. Here, we demonstrate a novel and potentially very precise method for making intensity measurements based on the atomic stabilization of electromagnetic field-strength. For ease of reference, and by analogy to atomic clocks, we refer to this field-strength stabilization system as an atomic candle. While the candle's original purpose was to create a field with long-term intensity stability, its very nature makes it ideal for detecting subtle amplitude changes in strong electromagnetic fields; a problem that is fundamentally different from detecting weak signals in the presence of noise. In this work, we discuss proof-of-principle experiments demonstrating the atomic candle's ability to make precise measurements of absorption coefficients and indices of refraction.