II Quantum Mechanical Limit in Optical Precision Measurement and Communication

Abstract

Publisher Summary This chapter discusses the standard and intrinsic quantum mechanical limits on optical precision measurement and communication. Nonclassical lights, such as a quadrature amplitude squeezed state, number-phase squeezed state (number state), and correlated photon pair circumvent the standard quantum limit (SQL) on photon generation. A quantum mechanical limit on the minimum energy cost per bit emerges if an optical homodyne or heterodyne receiver is used instead of a photon counter. The SQL on photon amplification stems from the fact that an ordinary linear amplifier amplifies the two conjugate observables simultaneously. The chapter discuses the intrinsic quantum limit, which determines the information extraction from a light wave. It emerges in the form of quantum mechanical channel capacity and Bohr's time-energy uncertainty principle. Applications of nonclassical lights, QND measurements, and single-observable amplifiers are also discussed.