cross-Kerr Nonlinearity Research Articles

Terahertz electromagnetically induced optical limiter in asymmetric coupled quantum wells

This paper explores the optical limiting (OL) characteristics of an input probe field within a closed-loop asymmetric coupled quantum well (ACQW) system. Our research reveals that the application of Terahertz (THz) coupling laser fields can induce the OL behavior within the THz domain in the ACQW. The study demonstrates that revers saturable absorption arises through cross-Kerr nonlinearity, contributing to the emergence of OL behavior. Additionally, it is shown that the self-defocusing is induced concurrently within the system, further enhancing nonlinear refractive OL effects. Furthermore, it is revealed that the properties of induced OL can be manipulated by adjusting the characteristics of the applied fields. The discovered outcomes hold potential utility in safeguarding sensors and detectors operating within the THz band.

A deterministic qudit-dependent high-dimensional photonic quantum gate with weak cross-kerr nonlinearity

High-dimensional quantum systems expand the Hilbert space, enabling the processing of more intricate information and the execution of wider quantum operations. The development of high-dimensional quantum systems relies significantly on the implementation of high-dimensional gates. In the paper, we propose a deterministic 4 × 4-dimensional controlled-not (CNOT) gate for a three-photon system, where encoding on the polarization-spatial state of a single photon acts as a 4-dimensional control qudit, meanwhile the polarized state of the remaining two photons serves as a 4-dimensional target qudit. The implementation of the gate leverages weak cross-kerr nonlinearities and X-homodyne detectors, which impose lower requirements on the interaction strength and demonstrate robustness against photon loss. In accordance with the measurement of the coherent state, the relevant classical feed-forward operations are employed to make high-dimensional CNOT gate effective. Additionally, the proposed scheme demonstrates a high successful probability as a result of the utilization of mature measurement methods and straightforward optical elements. Further, the fidelity of the CNOT gate is robust against photon loss and is approximate to 1 with the existing technology. Consequently, our deterministic protocol presents a promising approach for the practical realization of high-dimensional quantum computation for photon systems.

The impact of cross-Kerr nonlinearity on rotary photon drag and temporal cloaking in Sagnac interferometry

We theoretically explore the impact of cross-Kerr nonlinearity (CKN) on rotary photon drag (RPD) and temporal cloaking in a Sagnac interferometer. With the activation of CKN, significant improvements in RPD and temporal cloaking are observed. Drag angles of ±1×10−3 and ±5×10−3 radians are attained, similarly, temporal gaps of 10μ s, 12μ s and 13μ s are observed. In addition to the observed electromagnetically induced transparency window, the group refractive index is drastically enhanced, time delay/advance are tuned from pico-radians to micro-radians, and reduced relativistic group velocities are achieved by activating CKN within the system. Additionally, the transmission pulses intensities are observed to be reduced with the dragging phenomenon. The findings may have potential applications in controlled image coding, rotation sensing and secure communication technologies.

Complete analysis of hyperentangled Bell state in three degrees of freedom using Kerr effect and self-assisted mechanism

We present an efficient scheme for the complete hyperentangled Bell state analysis (HBSA) of photon system with polarization and two longitudinal momentum degrees of freedom (DOFs), resorting to weak cross-Kerr nonlinearity, linear optical elements and single photon detectors. In the process of distinguishing the 64 hyperentangled Bell states in three DOFs, the self-assisted mechanism is embedded, which makes our scheme simple and realizable. Moreover, we have discussed the applications of this complete HBSA scheme for high-capacity quantum communication protocols that are based on photonic hyperentanglement in three DOFs.

Complete four-dimensional Bell state measurement using weak cross-Kerr nonlinearity

In this paper, we present an efficient scheme for the complete analysis of the four-dimensional Bell state of the photon system in the path degree of freedom, resorting to the weak cross-Kerr nonlinearity and linear optics. In our scheme, the measurements on two probe coherent states are used for obtaining the bit information of high-dimensional entanglement, and the linear optical elements and single-photon detectors are used for obtaining the relative phase information of high-dimensional entanglement. With these two independent processes, the 16 orthogonal four-dimensional path Bell states can be completely distinguished from each other. This simple and realizable scheme may have useful applications in the quantum information technology based on high-dimensional entanglement.

Kerr-effect-based quantum logical gates in decoherence-free subspace

The decoherence effect caused by the coupling between the system and the environment undoubtedly leads to the errors in efficient implementations of two (or three) qubit logical gates in quantum information processing. Fortunately, decoherence-free subspace (DFS) introduced can effectively decrease the influence of decoherence effect. In this paper, we propose some schemes for setting up a family of quantum control gates, including controlled-NOT (CNOT), Toffoli, and Fredkin gates for two or three logical qubits by means of cross-Kerr nonlinearities in DFS. These three logical gates require neither complicated quantum computational circuits nor auxiliary photons (or entangled states). The success probabilities of three logical gates are approximate 1 by performing the corresponding classical feed-forward operations based on the different measuring results of the X-homodyne detectors, and their fidelities are robust against the photon loss with the current technology. The proposed logical gates rely on only simple linear-optics elements, available single-qubit operations, and mature measurement methods, making our proposed gates be feasible and efficient in practical applications.

Generation of five-photon hyperentangled cluster state with three-photon GHZ state and Bell state via weak cross-Kerr nonlinearity

Generation of five-photon hyperentangled cluster state with three-photon GHZ state and Bell state via weak cross-Kerr nonlinearity

Noise-resilient phase transitions and limit-cycles in coupled Kerr oscillators

In recent years, there has been considerable focus on exploring driven-dissipative quantum systems, as they exhibit distinctive dissipation-stabilized phases. Among them dissipative time crystal is a unique phase emerging as a shift from disorder or stationary states to periodic behaviors. However, understanding the resilience of these non-equilibrium phases against quantum fluctuations remains unclear. This study addresses this query within a canonical parametric quantum optical system, specifically, a multi-mode cavity with self- and cross-Kerr non-linearity. Using mean-field (MF) theory we obtain the phase diagram and delimit the parameter ranges that stabilize a non-stationary limit-cycle phase. Leveraging the Keldysh formalism, we study the unique spectral features of each phase. Further, we extend our analyses beyond the MF theory by explicitly accounting for higher-order correlations through cumulant expansions. Our findings unveil insights into the modifications of the open quantum systems phases, underscoring the significance of quantum correlations in non-equilibrium steady states. Importantly, our results conclusively demonstrate the resilience of the non-stationary phase against quantum fluctuations, rendering it a dissipation-induced genuine quantum synchronous phase.

Decoherence-induced cross-Kerr nonlinearity for quantum entanglement

In this paper, we show that the cross-Kerr nonlinearity is induced by the ground-state decoherence in a Λ system even under the exact one- and two-photon resonance conditions, which is attributed to the fact that the dark-state resonance is broken slightly. By adiabatically eliminating the atomic variables, we find that the decoherence results in a frequency shift of cavity detuning and the two cavity fields experience cross-Kerr nonlinearity by choosing appropriate parameters. As a consequence, the internal nonlinear effects are responsible for the generation of light entanglement, which is verified by our numerical results. The present scheme demonstrates that the decoherence plays a positive role in controlling quantum entanglement, which may be useful for quantum information processing.

Effects of dual cross Kerr non-linearity on the manipulation of rotary photon drag

Effects of dual cross Kerr non-linearity on the manipulation of rotary photon drag

Control over magneto-optical plasmon rotation with Doppler broadening and cross-Kerr non-linearity

We investigate the impacts of cross-Kerr non-linearity and Doppler broadening on the magneto-optical rotation (MOR) induced in surface plasmon polaritons (SPPs) located at the interface of a metalic medium and a 4-level atomic system. In this paper, the external static magnetic field and a weak probe field under the cross-Kerr effect result in the birefringence enhancement of the system. Moreover, the incoherent effect of Doppler broadening can regulate the MOR of SPPs. Notably, the controlled MOR of SPPs can be leveraged for a variety of advantageous implementations in the fields of polarization spectroscopy, optical communication, nanoscale Faraday isolation, accurate metrology, as well as bio/chem sensing technologies.

Enhancing the Steady-State Entanglement between a Laguerre–Gaussian-Cavity Mode and a Rotating Mirror via Cross-Kerr Nonlinearity

Quantum entanglement will play an important role in future quantum technologies. Here, we theoretically study the steady-state entanglement between a cavity field and a macroscopic rotating mirror in a Laguerre–Gaussian-(LG)-cavity optomechanical system with cross-Kerr nonlinearity. Logarithmic negativity is used to quantify the steady-state entanglement between the cavity and mechanical modes. We analyze the impacts of the cross-Kerr coupling strength, the cavity detuning, the input laser power, the topological charge of the LG-cavity mode, and the temperature of the environment on the steady-state optomechanical entanglement. We find that cross-Kerr nonlinearity can significantly enhance steady-state optomechanical entanglement and make steady-state optomechanical entanglement more robust against the temperature of the thermal environment.

Refined Fredkin gate assisted by cross-Kerr nonlinearity

Resource-efficient quantum information processing is equal to the minimal cost of the quantum resources required by quantum logic gates to a certain extent. In this paper, we propose a refined scheme for setting up a polarized Fredkin gate assisted by weak cross-Kerr nonlinearity, X-homodyne detectors, and some linear optical elements. The realization of the Fredkin gate is definite and has a highly successful probability of being close to the unit, which is feasible with the current technology. Moreover, in contrast to the Fredkin gates that have been proposed, the scheme has the advantages of requiring less quantum resource without auxiliary photons, comparatively simplified circuits, lower requirements on the interaction strength, and robustness against photon loss, thus it can be used for scalable quantum computation.

Entanglement Purification for Logic-Qubit of Photon System Based on Parity Check Measurement Gate.

It has been found that logic-qubit entanglement has great potential for applications in quantum communication and quantum networks in recent years. However, along with the effects of noise and decoherence, the fidelity of the communication transmission can be greatly reduced. In this paper, we investigate the entanglement purification of logic bit-flip error and phase-flip error in polarization logic-qubit entanglement based on the parity-check measurement (PCM) gate, which is constructed by the cross-Kerr nonlinearity and used to distinguish the parity information of two-photon polarization states. The probability of entanglement purification is higher than the scheme using the linear optical method. Moreover, the quality of logic-qubit entangled states can be improved by a cyclic purification process. This entanglement purification protocol will be useful in the future when faced with long-distance communication with logic-qubit entanglement states.

Low-light-level spin–orbit splitting via structured light cross-Kerr interaction in coherent atomic media

We explore the spin–orbit coupling (SOC) mechanism for structured light in coherent atomic media with low-light-level cross-Kerr nonlinearity. Using the five-level M-type electromagnetic induced transparency (EIT) system as a prototype, we show that spin–orbit splitting for a weak spinor image can be generated by a weak trigger field carrying orbital angular momentum (OAM) at low-light intensity. By quantum-optical analogy, the paraxial focusing and defocusing of the two pseudo-spin states in the spinor image can be governed by a Pauli-like equation. More importantly, by changing the EIT parameters, especially the topological charge of the weak trigger field, the SOC-induced radial quantization of the spinor image can be rather significant, giving rise to positive or negative OAM-OAM mode separation in free space. This suggests that the separation can be flexibly controlled due to strong image-vortex interaction based on few-photon cross-Kerr modulation. Our findings may have the potential for all-optical OAM multiplexing and demultiplexing of structured light fields toward few-photon quantum control and multimode communication.

Giant cross-Kerr nonlinearity in the metal nanoparticles-graphene nanodisks-quantum dots hybrid system with low light intensity for photovoltaic devices

Giant cross-Kerr nonlinearity in the metal nanoparticles-graphene nanodisks-quantum dots hybrid system with low light intensity for photovoltaic devices

Simultaneous quantum squeezing of light polarizations and atomic spins in a cold atomic gas

We present a scheme to realize simultaneous quantum squeezing of light polarizations and atomic spins via a perturbed double electromagnetically induced transparency (DEIT) in a cold four-level atomic ensemble coupled with a probe laser pulse of two polarization components. We derive two coupled quantum nonlinear Schr\"odinger equations from Maxwell-Heisenberg-Langevin equations describing the quantum dynamics of the atoms and the probe pulse and develop a quantum theory of vector optical soliton (VOS), which have ultraslow propagation velocity and extremely low generation power. We solve the non-Hermitian eigenvalue problem describing the quantum fluctuations on the background of the VOS and rigorously prove that all fluctuation eigenmodes (including continuous modes and four zero modes) obtained constitute a biorthonormal and complete set. We find that, due to the giant self- and cross-Kerr nonlinearities contributed by the perturbed DEIT, a large polarization squeezing of the probe pulse can be realized. We also find that, together with the polarization squeezing of the probe pulses, a significant squeezing of atomic spins also occurs simultaneously. The results of the simultaneous squeezing of light polarizations and atomic spins by using only a coherent probe pulse reported here opens a route for uncovering the unique property of the quantum interface between light and atomic ensembles and also for applications in quantum information and precision measurement.

Single photons versus coherent-state input in waveguide quantum electrodynamics: Light scattering, Kerr, and cross-Kerr effect

While the theoretical studies in waveguide quantum electrodynamics predominate with single-photon and two-photon Fock-state (photon number states) input, the experiments are primarily carried out using a faint coherent light. We create a theoretical toolbox to compare and contrast linear and nonlinear light scattering by a two-level or a three-level emitter embedded in an open waveguide carrying Fock-state or coherent-state inputs. We particularly investigate light transport properties and the Kerr and cross-Kerr nonlinearities of the medium for the two types of inputs. A generalized description of the Kerr and cross-Kerr effect for different types of inputs is formulated using the first-order correlation function to compare the Kerr and cross-Kerr nonlinearity between two photons in these models.

Conventional and unconventional photon blockade with cross-Kerr nonlinearity

Conventional and unconventional photon blockade with cross-Kerr nonlinearity

Unconventional photon blockade induced by the self-Kerr and cross-Kerr nonlinearities

Unconventional photon blockade induced by the self-Kerr and cross-Kerr nonlinearities