The Quantum Noise Limit for a Specific Measurement

E. M. Kessler, Igor Lovchinsky, Alexander O. Sushkov +1 more

We propose and analyze a new approach based on quantum error correction (QEC) to improve quantum metrology in the presence of noise. We identify the conditions under which QEC allows one to improve the signal-to-noise ratio in quantum-limited measurements, and we demonstrate that it enables, in certain situations, Heisenberg-limited sensitivity. We discuss specific applications to nanoscale sensing using nitrogen-vacancy centers in diamond in which QEC can significantly improve the measurement sensitivity and bandwidth under realistic experimental conditions.

Paul Busch, Teiko Heinonen, PEKKA J. LAHTI

Sohitri Ghosh, Daniel Carney, Peter S Shawhan +1 more

The quantum measurement of any observable naturally leads to noise added by the act of measurement. Approaches to evade or reduce this noise can lead to substantial improvements in a wide variety of sensors, from laser interferometers to precision magnetometers and more. In this paper, we develop a measurement protocol based upon pioneering work by the gravitational wave community which allows for reduction of added noise from measurement by coupling an optical field to the momentum of a small mirror. As a specific implementation, we present a continuous measurement protocol using a double-ring optomechanical cavity. We demonstrate that, with experimentally relevant parameters, this protocol can lead to significant backaction noise evasion, yielding measurement noise below the standard quantum limit over many decades of frequency.

Hans Martens, Willem M. de Muynck

Lars Lading, Thomas Martini Jørgensen

A quantum-limited light-scattering system is considered. The spatial configuration that maximizes a given figure of merit is investigated, assuming that the emitted light has Poisson photon statistics. A specific system for measuring the velocity of a small particle is considered as an example. An optimum spatial code is found for the case of dominating intrinsic signal noise. The robustness of this solution is discussed in relation to the case of dominating background noise.

J.S.S. Whiting