Researches On Improving The Entanglement Of Optomechanical System By Using Continuous Measurement And Realizing One-way Steering Of Output Field By Filtering

Quantum entanglement is an important concept in two-body and multi-body quantum mechanics,and is closely related to quantum nonlocality.In recent years,with the continuous development of quantum information technology,the heat of quantum entanglement has been continuously improved,and a large number of quantum experiments have been carried out around entanglement.Among the cavity optomechanical system,some related quantum effects have been achieved,such as entangled states of optomechanics of continuous and discrete variables,and Gaussian entanglement between two mechanical oscillators.However,the entanglement in the stability region is generally small because of the dissipation of the cavity optomechanical system.Therefore,this paper aims to improve the entanglement of the three-mode cavity optomechanical system composed of two cavity modes and one mechanical oscillator by using the quantum control method of time-continuous measurement.It is found that although there is quantum entanglement between the cavity mode and the oscillator before the measurement,the entanglement strength is small and the stability region of the system is narrow.After the measurement of the cavity mode,the entanglement strength between the cavity mode and the oscillator of the system is obviously improved,and the range of the stability region becomes wider.And the entanglement increases with the increase of measurement efficiency under the same parameter.The above results have achieved our goal.The term steering was first used by schrodinger to describe the "ghostly action at a distance" phenomenon proposed by Einstein,Podolski and Rosen(EPR)in their famous paradox.Subsequently,the concept of steering was strictly defined by Wiseman et al.,revealing that quantum steering is a Quantum nonlocality between quantum entanglement and Bell non-locality.Distinct from entanglement and Bell nonlocality,steering is intrinsically asymmetric with respect to the two particles and therefore directional.There may exist one-way steering which allows us to steer the states of one particle by measuring the other but not vice versa.Its unique nature makes quantum steering an important physical resource for quantum secure transmission.Nowadays,quantum steering has been experimentally realized in a variety of systems,such as discrete variable photonic systems and continuously variable optical systems.The main research in this paper is to realize quantum one-way steering between two output fields in a three-mode system by filtering.First,we use the Fourier transform to change the operator from the time domain to the frequency domain,and write the operator form of the output field based on the input and output relationship.A specific output field with a certain line width and center frequency is then selected by the filter function.In this way,the correlation matrix of the output field is obtained.Finally,quantum one-way steering between the two output fields is achieved by adjusting the parameters.