Nonreciprocal Quantum Entanglement And Their Manipulation In Spinning Optomechanical Systems

Quantum entanglement is a unique property of quantum mechanics,which reflects the correlations and the inseparability between the subsystems of the entire quantum system.In addition,quantum entanglement also plays an important role in the development of the second-generation quantum technologies,which provides quantum resources for the field of quantum information processing and quantum precision measurement such as quantum computing,quantum communication or quantum radar.Therefore,the research on quantum entanglement not only has profound scientific significance,but also provides extensive applications.However,quantum entanglement always tends to be destroyed by various intrinsic impurities and random noises in the open quantum systems.So far,it has already become a challenging issue to find ways for protecting and recovering quantum entanglement in the field of quantum technology.On the other hand,nonreciprocal devices usually have advantages in protecting laser source,avoiding quantum decoherence,and implementing logic operations,which plays a very important role in the field of both classical and quantum information processing.In recent years,in view of rapid advances in materials science and micro-nano processing technology,remarkable breakthroughs have been achieved in the development of nonreciprocal devices in optics,acoustics,and electronics.However,most previous studies have mainly focused on the classical applications of nonreciprocity,such as isolators and circulators,while its application in quantum engineering has hardly been explored until very recent years.In this thesis,based on the cavity-spinning optomechanical systems we have studied the physical mechanism of generating,manipulating,and detecting non-reciprocal macro-micro(macro)quantum entanglement,explore approaches to create non-reciprocal macro-micro(macro)quantum entanglement.We proposed a new scheme to achieve nonreciprocal optomechanical and mechanical entanglement,and revealed the counterintuitive property of non-reciprocal manipulation in the suppression of quantum decoherence.We expect our result may provide key tools for the protection and manipulation of quantum resources.By using the cascaded optomechanical system composed of two spinning microcavities,we further studied the non-reciprocal quantum entanglement between macroscopic mechanical oscillators,which provides a new method for quantum control of massive objects.The main innovative results obtained in this thesis are as follows:1.We propose a theoretical scheme to generate nonreciprocal optomechanical entanglement between optical photons and mechanical oscillator based a cavity-spinning optomechanical system.It is found that by splitting the counterpropagating lights of a spinning resonator via the Sagnac effect,photons and phonons can be entangled strongly in a chosen direction but fully uncorrelated in the other.This makes it possible both to realize quantum nonreciprocity even in the absence of any classical nonreciprocity.2.We reveal the physical mechanism to protect and retrieve nonreciprocal optomechanical entanglement.We investigate quantum decoherence of the cavity optomechanical system by the use of Heisenberg-Langevin equation and the Lindblad master equation,respectively.It is found that the cavity spinning and the driving of the cavity field can suppresses quantum decoherence of the nonreciprocal optomechanical entanglement.We show how to keep the optimal nonreciprocal optomechanical entanglement in a chosen direction against losses.3.We propose a new scheme to detect nonreciprocal optomechanical entanglement,and demonstrate the experimental feasibility of achieving nonreciprocal optomechanical entanglement.It is found that the detected optomechanical entanglement in the output field keeps the quantum nonreciprocity of the intracavity field.Moreover,by choosing proper angular speed of the spinning resonator and the line-width of the probe field,we also find that the influence of thermal noise can be further suppressed,thereby improving the quantum coherence of the system.In addition,to demonstrate the experimental feasibility of achieving nonreciprocal optomechanical entanglement,we also analyze the stability of the coupling between an optical telecommunication fiber and a spinning resonator.4.We present a theoretical scheme to create nonreciprocal macro-macro entanglement between two mechanical oscillators based on two coupled cavityspinning optomechanical systems,in which two spinning cavities are connected with each other through the fibre coupling.It is found that the nonreciprocal macro-macro mechanical entanglement can be manipulated by the use of the Sagnac effect produced by the cavity spinning.Such nonreciprocal macromacro entanglement provides a way to protect and engineer quantum resources by utilizing diverse nonreciprocal devices,for building noise-tolerant quantum processors,realizing chiral networks,and backaction-immune quantum sensors.