Abstract
A new type of quantum interferometer was recently realized that employs parametric amplifiers (PAs) as the wave splitting and mixing elements. The quantum behavior stems from the PAs, which produce quantum entangled fields for probing the phase change signal in the interferometer. This type of quantum entangled interferometer exhibits some unique properties that are different from traditional beam splitter-based interferometers such as Mach–Zehnder interferometers. Because of these properties, it is superior to the traditional interferometers in many aspects, especially in the phase measurement sensitivity. We will review its unique properties and applications in quantum metrology and sensing, quantum information, and quantum state engineering.
Highlights
Interferometry, a technique based on wave interference, played a crucial part in the development of fundamental ideas in physics as well as in the technological advances of mankind
It is known that the two outputs of PA1 are entangled in the continuous variables of phases and amplitudes49,50 and two entangled fields can be transformed by a 50:50 beam splitter into two independent squeezed states with noise reduced at orthogonal quadratures
If the signal and the internal modes are in the EPRtype entangled state such as those generated from the first parametric amplifiers (PAs), Xs(in) and Xi(nitn) are quantum mechanically correlated so that ⟨Δ2(Xs(in) + λXi(nitn))⟩ can be smaller than the corresponding vacuum value of 1 + λ2
Summary
Interferometry, a technique based on wave interference, played a crucial part in the development of fundamental ideas in physics as well as in the technological advances of mankind. Experimental efforts and progress were made in the generation and application of these quantum states to optical interferometry systems.2,3 Such a technique was recently applied to km-scale large size interferometers with the goal of improving the sensitivity for gravitational wave detection.. Because of the involvement of nonlinear optical processes, these nonlinear interference effects have some interesting applications in spectroscopy, optical imaging, and spatial and temporal shaping.31,32 They can be mostly understood with classical wave theory. At the quantum level of single photons when the gain of the parametric amplifiers is low, interferometers consisting of spontaneous parametric downconversion were used to study two-photon or multi-photon interference, which cannot be explained by classical theory These quantum interferometric effects are the basis for optical quantum information sciences..
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