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We investigate theoretically an optomechanical system composed of an optical mode and a mechanical mode interacting through first-order coupling and second-order coupling in the presence of a Kerr nonlinear medium. We study how the nonlinearities (second-order optomechanical coupling and Kerr nonlinearity) alter the optical output spectrum, optical quadrature squeezing and optomechanical entanglement. It is shown that the intensity of the output optical spectrum decreases drastically with an increase in second-order optomechanical coupling while it increases significantly with an increase in Kerr nonlinear parameter. More interestingly, by choosing suitable second-order optomechanical coupling and detuning of the optical cavity field, one can achieve strong squeezing of the cavity light field. Further, these nonlinearities play an important role in creating robust optomechanical entanglement between optical and mechanical modes. Hence, the presence of various nonlinearities in the system can be a good platform for achieving the squeezing of light and robust optomechanical entanglement which can be used in realizing better quantum optomechanical devices.

We investigate the optical response of a hybrid cavity quantum-electrodynamics system consisting of a quantum dot embedded in an optomechanical photonic crystal cavity. The system is coupled to an ...

Objective: This paper theoretically studies a hybrid optomechanical system embedded with two coupled quantum dots (CQDs) and a third-order Kerr nonlinear medium inside the cavity. The optical bistability and absorption spectrum are analyzed for the proposed system. Methods: From the Hamiltonian which describes the proposed system, a set of quantum Langevin equations are derived. Using these equations of motion, the steady-state mean field analysis is done which gives the phenomena of optical bistability. The performance of the optical switch is also analyzed in terms of gain and switching ratio. Further, the absorption spectrum of the system is derived and analyzed from the fluctuation dynamics. Results: The optical bistability has the potential to design tunable all-optical switches. The absorption spectra display peculiar characteristics of negative absorption (transparency dip). The transparency dips are found to be strongly dependent on the frequency of the mechanical resonator. The results of our investigation reveal that the proposed system can be used as an optical switch and has numerous other applications in quantum communication systems.

Vibrational strong coupling provides a convenient way to modify the energy of molecular vibrations and to explore the control of chemical reactivity. In this work, we theoretically report the various vibrational anharmonicities that modulate the dynamics of optomechanically coupled W(CO)6-cavity. The optomechanical free-space cavity consists of movable photonic crystal membrane, which creates photonic bound states to interact with the molecular vibration. This coupled system is used for realizing strong optomechanical dispersive or dissipative type coupling, which provides a platform to explore the new regimes of optomechanical interaction. The addition of different strong coupling and mechanical (nuclear) anharmonicities to the optical cavity establishes a modified splitting dynamics in the absorption spectrum and shows that the ground-state bleach of coupled W(CO)6-cavity has a broad, multisigned spectral response. This work demonstrates the possibility of systematic and predictive modification of the multimode spectroscopy of optomechanical W(CO)6-cavity polariton system.

Coherent and tunable light-matter interaction in cavity quantum electrodynamics (C-QED) has attracted much attention for its fundamental importance and applications in emerging areas of quantum technologies. In this work, we propose a hybrid C-QED system comprising embedded quantum dot molecules (QDMs) in a primary photonic crystal (PhC) optomechanical cavity, which is further coupled to an auxiliary PhC cavity via a single-mode waveguide. We investigate the effect of the QDMs, mechanical oscillator, and the feedback from the auxiliary cavity on the multistability response shown by the mean intracavity photons in the primary optomechanical cavity. Tuning the various system parameters can control optical multistability. We further study the absorption spectra showing distinct characteristics of negative absorption (transparency dip), which strongly depend on mechanical resonator frequency. Thus, the proposed model is valuable for practically realizing efficient all-optical switching devices at low power and in various other quantum sensing devices.

We explore the phenomena of quadrature squeezing of photons in the Two-Photon Dicke Model under the mean-field approximation in the thermodynamic limit. The strength of photon squeezing is maximized in the region where the coupling strength is of the same order of magnitude as one of the fundamental frequency of the system. This particular region is termed as the unbounded region. The squeezing of the photonic quadratures can be observed only in the superradiant phase where the squeezing is well beyond the standard quantum limit both near the quantum critical point as well as the unbounded region. However, prolonged squeezing is only obtained in the latter case. Furthermore, we explore the critical behavior of photon squeezing near the unbounded region., 11 pages, 6 figures

We theoretically investigate optical bistability/multistability for all optical switching signature in a hybrid semiconductor microcavity system comprising a quantum well and a Kerr nonlinear subst...

We propose to achieve quantum optical nonreciprocity in a hybrid qubit-optomechanical solid-state system. A two-level system (qubit) is coupled to a mechanically compliant mirror (via the linear Jaynes–Cummings interaction) placed in the middle of a solid-state optical cavity. We show for the first time that the generated optical bistability exhibits a bi-directional photonic switch, making the device a suitable candidate for a duplex communication system. On further exploring the fluctuation dynamics of the system, we found that the proposed device breaks the symmetry between forward and backward propagating optical modes (optical nonreciprocity), which can be controlled by tuning the various system parameters, including the qubit, which emerges as a new handle. The device thus behaves like an optical isolator and hence can store optical data in the acoustic mode, which can be retrieved later.

We theoretically investigate the four wave mixing (FWM) and normal mode splitting (NMS) in coupled double quantum dots cavity system in the presence of a third-order Kerr nonlinear χ ( 3 ) medium. The FWM generated in the system has narrow spectral width and this can be tuned by nonlinear medium strength, the coupling strength between two coupled quantum dots and pump strength. Further, we study NMS that can also be tuned by various physical parameters and show that energy exchange between different modes is possible. The proposed model have potential applications in the field of quantum information processing.

We theoretically investigate the optical and mechanical properties of a double cavity optomechanical system with one stationary and two harmonically bound mirrors. We show that it is possible for the mechanical mirrors in this system to posses negative effective mass. Working within the strong coupling and the resolved sideband regime, we show that the displacement of the middle resonator is multistable under certain constrains. We also point to the existence of optomechanically induced absorption (OMIA) and Fano resonance. Owing to the negative effective mass, our scheme can be exploited in the study of quantum optomechanical metamaterials., Comments are welcome

We propose a scheme to implement a strong photon blockade with two interacting quantum dots, optically coupled to a semiconductor microcavity. The photon blockade effect is enhanced by simultaneously driving the microcavity and one of the two quantum dots with two classical laser fields. Quantum interference effect with different transition paths is the mechanism responsible with photon blockade. This system has been found to be a tunable source of single or two-photon with applications in solid state quantum computation and quantum information processing.

We study theoretically the photon statistics of the field emitted from two optically coupled semiconductor microcavities each containing a quantum well. The emission is determined by the interplay between exciton-photon coupling in each quantum well and internal interaction between the two optically coupled microcavities. A high degree of coherent control and tunability via the quantum well-cavity coupling strength and photon tunneling over the photon statistics of the transmitted field can be achieved. We demonstrate that the optical property of radiation emitted by one quantum well can be controlled by the properties of the second quantum well. This result has the potential to be used in quantum information processing. We show that the exciton-photon coupling influences the polariton resonances in the intensity spectrum of the transmitted field. The results obtained in this investigation has the potential to be used for designing efficient controllable all-optical switch and high sensitive optical sensor., Comment: Accepted in Optik

We theoretically study a hybrid system containing of a single quantum dot (QD) embedded in a solid state microcavity which interact with the deformation potential associated with the lattice vibration and quantized cavity mode. We investigate optical bistability, mechanically induced absorption (MIA) and Fano resonance in the present system. We find that the bistability can be controlled by the QD-cavity mode coupling. We further show that the normalized power transmission displays anomalous dispersion indicating that the system can be used to generate slow light. This study also demonstrate the possibility of using the system as an all optomechanical Kerr switch.

The ability to design, fabricate and control systems that can convert photons with dissimilar frequencies has technological implications in classical as well as quantum communications. Laser heating and thermal-mechanical motion in conventional micro/nanoscale optomechanical systems hamper the use of these systems in quantum information processing networks. In contrast, we propose an unconventional system comprising of a bulk quartz crystal placed within a Fabry-Perot cavity. The pumping laser is in the far-infrared region. We explore the possibility of efficient mode conversion between two optical modes supported by the system, mediated by the bulk acoustic phonons of the quartz crystal. Unlike the earlier optomechanical systems, the dark mode in our proposed system is not decoupled from the mechanical mode and yet it enables the efficient mode conversion. The novel results found in our study can be used to harness the dark state for quantum state transfer. The proposed system is robust against excessive heating., Comment: 17 pages and 5 figures

We investigate the optical properties of a hybrid solid-state optomechanical microcavity containing two coupled quantum wells interacting with the cavity mode in the presence of a third-order nonlinear medium and a mechanically compliant distributed Bragg reflector (MC-DBR). The MC-DBR interacts with the cavity mode via the nonlinear radiation pressure effect. The steady state mean-field analysis shows the existence of optical bistability, which can be utilized to design all optical tunable switch. The coupling between the two quantum wells, the interaction between the excitons and the optical mode, the Kerr nonlinearity, and the optomechanical interaction can be tuned to operate the optical switch at lower input laser power. The fluctuation dynamics demonstrate the presence of optomechanically induced transparency (OMIT) and optomechanically induced absorption (OMIA). We find that both OMIT and OMIA can be manipulated efficiently by optomechanical coupling strength and the quantum well tunneling rate.

We theoretically investigate the optical response in a hybrid quantum optomechanical system consisting of two optically coupled micro-cavities in which a two-level system (qubit) is embedded on a movable membrane. The qubit can either be a defect which interacts with the mechanical oscillator via the linear Jaynes-Cummings interaction or a superconducting charge qubit coupled with the mechanical mode via nonlinear interaction. We find that coherent perfect transmission (CPT), coherent perfect synthesis (CPS) and optomechanically induced absorption (OMIA) can be generated by suitably adjusting the system parameters. We find that the qubit and its interaction with the mechanical oscillator emerges as a new handle to control these quantum optical properties. The presence of the qubit results in four points where CPT and CPS can be realized compared to the pure optomechanical case (i.e. in the absence of qubit) where only three points are attained. This shows that the presence of the qubit gives us more flexibility in choosing the appropriate parameter regime where CPT and CPS can be attained and controlled. We also find that OMIA shows three distinct peaks both in the linear and nonlinear cases. In the absence of the qubit, OMIA is converted to optomechanically induced transmission (OMIT). An increase in in the qubit decay rate also shows a transition from OMIA to OMIT. Our study reveals that the optical response of the nonlinear case is relatively rapid (more sensitive) compared to the linear case to changes in the system parameters. This demonstrates the potential use of this hybrid system in designing tunable all-optical-switch and photon-router both of which forms an important element of a quantum information network., 23 pages, 12 figures

We systematically study the influence of simultaneously modulating the input laser intensity and quantum dot (QD) resonance frequecy on the mean-field dynamics, fluctuation energy transfer and entanglement in a optomechanical semi-conductor resonator embedded with a QD. We show that the modulation and the hybrid system can be engineered to attain the desired mean-field values, control the fluctuation energy transfer and the entanglement between the various degrees of freedom. A remarkably high degree of entanglement can be achieved by modulating only the QD frequency. The interplay between the two modulations leads to an entanglement which lies between that generated solely by modulating either the QD or the pump laser intensity. A transition from low stationary to large dynamical entanglement occurs as we switch on the modulation. This study opens up new possibilities for optimal control strategies and can be used for data signal transfer and storage in quantum communication platforms., Comment: Comments are welcome

We theoretically investigate optical bistability, mechanically induced absorption (MIA) and Fano resonance of a hybrid system comprising of a single quantum dot (QD) embedded in a solid state microcavity interacting with the quantized cavity mode and the deformation potential associated with the lattice vibration. We find that the bistability can be tuned by the QD-cavity mode coupling. We further show that the normalized power transmission displays anomalous dispersion indicating that the system can be used to generate slow light. We also demonstrate the possibility of using the system as all optomechanical Kerr switch., 19 pages

We investigate a double cavity optomechanical system(OMS) generating single and double Fano resonance(multi Fano). By altering a single parameter, the tunneling rate $g$ of the middle mirror, we are able to switch between single and double Fano line shapes. The first spectral line shape is stronger in the case of multi Fano than in the case of single Fano. Also the behaviour of steady state value of the displacement of the middle mirror with respect to $g$, heavily influences the behaviour of double Fano lines in our scheme. This tunability along-with using a single pump and signal/probe laser has an added advantage in situations where only low power consumption is available., 16 pages

We theoretically study the polariton multistability in a solid state based optomechanical resonator embedded with a quantum well and aχ(2)second order nonlinear medium. The excitonic transition inside the quantum well is strongly coupled to the optical cavity mode. The polariton formed due to the mixing of cavity photons and exciton states are coupled to the mechanical mode which gives rise to the bistable behavior. A transition from bistability to tristability occurs in the presence of a strongχ(2)nonlinearity. Switching between bistability and tristability can also be controlled using exciton-cavity and optomechanical coupling making the system highly tunable. Tristability appears at low input power making it a suitable candidate for polaritonic devices which requires low input power.

Quantum devices exhibiting optical non-reciprocity are indispensable for quantum information processing and communication technology. In this paper we propose a double cavity optomechanical system where the movable mirror of the cavity is linearly coupled with a qubit placed inside the cavity. We study the effect of this mechanical mode - qubit linear interaction on time reversal symmetry i.e, optical non-reciprocity and prove that mechanical mode - qubit interaction can be used as a new tool to control optical non-reciprocity.

The future of quantum communication systems and quantum networks heavily rely on the ability to fabricate and coherently control the conversion of photons between different modes based on a solid-state plateform. In this work, we propose and theoretically investigate a scheme to optomechanically control coherent mode conversion of optical photons by utilizing two optically coupled hybrid semiconductor microcavities containing a quantum dot (QD). One of the microcavity is pumped by an external laser and the second cavity is driven by light emitted by the QD that is embedded in the interface separating the two microcavities. The semiconductor microcavities can be fabricated using distributed Bragg reflectors (DBR) and can be made movable. We have demonstrated that photon-mode-conversion efficiency can be coherently manipulated by the optomechanical mode under appropriate conditions., Comment: comments welcome

We study controlled spin transport through a two-dimensional (2D) spin-orbit coupled quantum ring of finite width. Complete analytical expressions for the energy spectrum and wave function of a 2D ring are obtained in the presence of both an external magnetic field and Rashba spin-orbit interaction. These results have been used to investigate the magnetoconductance of the ring in which an interface electric field leads to the Rashba mechanism. Nonperiodicity of the ground-state angular momentum transition with respect to the external magnetic field is observed for a 2D ring which is in contrast to the perfectly periodic transition spectrum of the one-dimensional (1D) ring. Our analytical model has successfully reproduced the salient features of the magnetoconductance of the ring. In 1D as well as 2D ring geometries, the probability amplitude for the transfer of electron spin, polarized in the direction of an external magnetic field, is found to be maximum irrespective of the polarization of the incoming spin. Since the spin polarization of the transmitted electron changes continuously with Rashba coupling, this system can act as a tunable spin switch electrically controlled by gate voltage.

Quantum machine learning is a relatively new research field that aims to combine the dramatic performance advantage offered by quantum computing and the ability of machine learning algorithms to learn complex distributions of high-dimensional data. The primary focus of this domain is the implementation of classical machine learning algorithms in the quantum mechanical domain and study of the speedup due to quantum parallelism, which could enable the development of novel techniques for solving problems such as quantum phase recognition and quantum error correction optimization. In this paper, we propose a hybrid quantum machine learning pipeline for predicting the atomization energies of various molecules using the nuclear charges and atomic positions of the constituent atoms. Firstly, we will be using a deep convolutional auto-encoder model for the feature extraction of data constructed from the eigenvalues and eigenvector centralities of the pairwise distance matrix calculated from atomic positions and the unrolled upper triangle of each Coulomb matrix calculated from nuclear charges, and we will then be using a quantum regression algorithm such as quantum linear regression, quantum radial basis function neural network and, a quantum neural network for estimating the atomization energy. The hybrid quantum neural network models do not seem to provide any speedup over their classical counterparts. Before implementing a quantum algorithm, we will also be using state-of-the-art classical machine learning and deep learning models such as XGBoost, multilayer perceptron, deep convolutional neural network, and a long short-term memory network to study the correlation between the extracted features and corresponding atomization energies of molecules.

We study the generation of atomic-squeezed states for a Bose-Einstein Condensate confined within the lossless optomechanical cavity using pondermotively squeezed light. We show that the radiation pressure coupling between the optical cavity field and mechanical motion of the cavity end mirror generates squeezing of light. This radiation pressure induced light squeezing gets transferred to the condensate atoms via Tavis-Cummings type interaction and results in squeezed-spin states. We further discuss the effect of optomechanical coupling on squeezed atomic states.

We investigate the optical bistable behavior for a weakly interacting two-species Bose-Einstein condensates inside a pumped optical cavity by considering the two possible regimes- the phase mixed regime and the phase segregated regime. We find that the cavity-pump detuning plays a significant role in controlling the threshold of the optical bistability and the constrast between the bistability values depending upon the state we are working in. We also demonstrate the occurence of normal mode splitting in the optical spectrum for both the regimes which further showing the position and amplitude discrepancies in the spectral peaks.

We study an optomechanical system in which the mechanical motion of a single trapped ion is coupled to a cavity field for the realization of a strongly quantum correlated two-mode system. We show that for large pump intensities the steady state photon number exhibits bistable behaviour. We further analyze the occurrence of normal mode splitting (NMS) due to mixing of the fluctuations of the cavity field and the fluctuations of the ion motion which indicates a coherent energy exchange. We also find that in the parameter regime where NMS exists, the steady state of the system shows continuous variable entanglement. Such a two-mode optomechanical system can be used for the realization of continuous variable quantum information interfaces and networks., Comment: comments welcome

We theoretically explore optical bistability for the possible signature of all-optical switching and their performance in a hybrid quantum optomechanical system comprising of two semiconductor microcavities coupled optically. One of the cavity is driven by an external amplitude-modulated pump laser while the second cavity, which contains a quantum dot, is indirectly driven by light transmitted from the first cavity and a transverse optical field. The generated bistable behavior due to optomechanical nonlinearity shows a typical optical switching behavior and it can be controlled by changing the laser power, QD cavity coupling, modulating amplitude/frequency and the optomechanical coupling. A clear signature of energy exchange between the mechanical and optical modes is visible from the mechanical displacement spectrum. These results suggest that the present system can be used in sensitive optical switches and optical sensors.

The quantum Rabi oscillations in a coherently driven quantum dot embedded in a high-Q doubly resonant semiconductor micro-cavity in the presence of a strong second-order nonlinear medium is investigated theoretically. It is shown that the χ(2) nonlinearity effect the Rabi oscillations in a significant manner.

We theoretically investigate the nonlinear effects in a hybrid quantum optomechanical system consisting of two optically coupled semiconductor microcavities containing a quantum dot and a Kerr nonlinear substrate.The steady state behavior of the mean intracavity optical field demonstrates that the system can be used as an all optical switch. We further investigate the spectrum of small fluctuations in the mechanical displacement of the movable distributed Bragg reflectors (DBR) and observe that normal mode splitting (NMS) takes place for high Kerr nonlinearity and pump power. In addition, we have shown that steady state of the system exhibits two possible bipartite entanglements by proper tuning of the system parameters. The entanglement results suggest that the proposed system has the potential to be used in quantum communication platform. Our work demonstrates that the Kerr-nonlinearity can effectively control the optical properties of the hybrid system, which can be used to design efficient optical devices., 27 pages, 8 figures