Cavity Quantum Electrodynamics Coherent Perfect Absorption And Nonclassical States Preparation

Absorption is one of the results from the interaction between light and matter.How to achieve perfect absorption always attracts a lots of attention.To achieve this goal efficiently,researchers are constantly experimenting with nature materials,artificial materials or struc-tures.In 2010,Chong et al.,from basic physics ideas such as anti-laser and time reversal,replaced the gain medium in the cavity by a dissipative medium,and then used two laser beams with the same amplitude and frequency to excite the cavity from opposite directions.By adjusting the system parameters,they realized the coherent perfect absorption(CPA).The realization of this technology has aroused the interest of researchers,and then they achieved CPA in structures and materials such as optical cavity,waveguide,one-dimensional photonic structure,ultra-thin structure,plasma,graphene,and metamaterials.The realization of CPA provides a theoretical and technical basics for the fabrication of all-optical switches,sen-sors,regulators,filters,etc.,and some of them have been realized in the laboratory.Due to the quantum effect,CPA has some new characteristics.Based on the full quantum theory,this paper studies CPA and its nonclassical state preparation,as well as building mechan?ical Greenberger-Horne-Zeilinger(GHZ)and cluster states by harnessing optomechanical quantum steerable correlations.Firstly,CPA is investigated in the quantum nonlinear regime of cavity quantum electro?dynamics(CQED),in which a single two-level atom couples to a single-mode cavity weakly driven by two identical laser fields.In the strong-coupling regime and due to the photon blockade effect,the weakly driven CQED system can be approximated into single-photon space.The condition of CPA in nonlinear region is obtained by the full quantum theory anal-ysis,In the quantum nonlinear regime,the incoherent dissipation processes such as atomic and photon decays place a lower bound for the purity of the intracavity quantum field.Under the CPA condition,the intracavity field always exhibits the quadrature squeezing property manifested by the quantum nonlinearity,and the outgoing photon flux displays the higher sub-Poissonian distribution.Next,an optical parametric oscillator(OPO)crystal and a frequency doubling laser are added to the above system.The frequency-doubled laser drives the mirror to produce a frequency-doubling photon.It decomposes into two low-frequency photons after through OPO crystal,and then the system is in two-photon excitation space.By selecting parameters,We obtained depth CPA:the single photon amplitude of output field is zero as well as the two-photon amplitude.In addition,the parameters are adjusted such that the single photon of output field is not zero,and two-photon amplitude of the output is zero.The output field are composed with single photon and multiphoton,while the latter is negligible.The system therefore can be regarded as an ideal single-photon source.Finally,We propose a feasible scheme for generating Gaussian GHZ and cluster states of multiple mechanical oscillators by pulsed cavity optomechanics.In our scheme,each optomechanical cavity is driven by a blue-detuned pulse to establish quantum steerable cor-relations between the cavity output field and the mechanical oscillator,and the cavity out-puts are combined at a beam-splitter a:rray with given transmissivity and reflectivity for each beam splitter.We show that by harnessing the light-mechanical steerable correlations,the mechanical GHZ and cluster states can be realized via homodyne detection on the ampli-tude and phase quadratures of the output fields from the beam-splitter array.These achieved mechanical entangled states can be viewed as the output states of an effective mechanical beam-splitter array with the mechanical inputs prepared in squeezed states with the light-mechanical steering.The effects of detection efficiency and thermal noise on the achieved mechanical states are investigated.The present scheme does not require externally inject-ed squeezing and it can also be applicable to other systems such as light-atomic-ensemble interface,apart from optomechanical systems.