We consider the problem of the measurement of very small displacements in the transverse plane of an optical image with a split photodetector. We show that the standard quantum limit for such a measurement, which is equal to the diffraction limit divided by the square root of the number of photons used in the measurement, cannot be overcome by use of ordinary single-mode squeezed light. We give the form of possible multimode nonclassical states of light, enabling us to enhance by orders of magnitude the resolution of such a measurement beyond the standard quantum limit.
© 2000 Optical Society of America
C. Fabre, J. B. Fouet, and A. Maître, "Quantum limits in the measurement of very small displacements in optical images," Opt. Lett. 25, 76-78 (2000)