Toward Quantum-limited Displacement Detection

John D. Teufel

Magnus T. L. Hsu, V. Delaubert, Ping Koy Lam +1 more

We derive the quantum noise limit for the optical beam displacement of a TEM00 mode. Using a multimodal analysis, we show that the conventional split detection scheme for measuring beam displacement is non-optimal with 80% efficiency. We propose a new displacement measurement scheme that is optimal for small beam displacement. This scheme utilises a homodyne detection setup that has a TEM10 mode local oscillator. We show that although the quantum noise limit to displacement measurement can be surpassed using squeezed light in appropriate spatial modes for both schemes, the TEM10 homodyning scheme out-performs split detection for all values of squeezing.

Hiroshi Yamaguchi, S. Miyashita, Y. Hirayama

Alfredo Luis

We analyze the quantum limit to the sensitivity of the detection of small displacements. We focus on the case of free particles and harmonic oscillators as the systems experiencing the displacement. We show that the minimum displacement detectable is proportional to the inverse of the square root of the mean value of the energy in the state experiencing the displacement (Heisenberg limit). We present a measuring scheme that reaches this limit using semiclassical states. We examine the performance of this strategy under realistic practical conditions by computing the effect of imperfections such as losses and nonunit detection efficiencies. This analysis confirms the robustness of this measuring strategy by showing that the experimental imperfections can be suitably compensated by increasing the mean energy of the input state.

Cindy A. Regal

V. Delaubert, Nicolas Treps, Magnus T. L. Hsu +4 more

We demonstrate a scheme based on homodyne detection with a TEM/sub 10/ local oscillator for optimum small displacement measurements beyond the quantum noise limit. It is demonstrated to be directly extendable to optimum tilt measurement.