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Nonclassical properties of two-mode squeezing-enhanced vacuum state
摘要： We present a new kind of two-mode squeezed vacuum state with two squeezing parameters. Different from the normal univariate two-mode squeezed vacuum state, this new state shows stronger squeezing effect, anti-bunching and entanglement. It is shown that the new squeezing parameter plays an important role in this state.
关键词： fidelity,entanglement,cross-correlation function,squeezing,antibunching effect
更新于2025-09-23 15:23:52
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Field-squeeze operators via coherent population trapping
摘要： We present a scheme to generate unitarily two-mode and four-mode ?eld squeezing in optical cavities with the near-resonantly dressed three-level atoms in the (cid:2) con?guration. The dressing ?elds open two coherent population trapping (CPT) windows, within which the atoms stay predominantly in the dark state and yield strong nonlinearities for both the dressing ?elds themselves and the other applied ?elds. The two-mode squeeze operator is separated from degrees of freedom of atoms in a common CPT window, and the multimode squeeze operator is segregated in different CPT windows. The resulting two-mode and multimode interaction strengths are at least one order higher than in the previous dispersive schemes, where all ?elds are far off resonant with the atoms. The present near-resonant scheme is robust to spontaneous emission since atoms are nearly trapped in a long-lived superposition state.
关键词： field squeezing,coherent population trapping,optical cavities,quantum optics,three-level atoms
更新于2025-09-23 15:23:52
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Dynamic Properties for BEC in an Optical Cavity with Atom-Photon Nonlinear Interaction
摘要： In this paper we investigate the dynamics of physical properties of the system introduced in Dimer et al. (Phys. Rev. A 75, 013804, 2007) and Zhao et al. (Phys. Rev. A 90, 023622, 2014) consisting of an ensemble of four-level atoms in Bose-Einstein condensate (BEC) state and a single-mode quantized field in which nonlinear interaction is taken into account. In fact, we start with a four-level atom and then explain how this model can be reduced to an effective two-level one via the adiabatic elimination. Also, our presentation is free of any classical approximation and so it is fully quantized. In this regard, we introduce the dynamical Hamiltonian of the system in terms of angular momentum operators and use the Dicke model to achieve the state of atomic sub-system. After obtaining the analytical solution of the state vector associated with the quantized BEC-field system, various physical properties such as atomic population inversion, quantum statistics of the field, squeezing in atomic and field subsystems as well as the degree of entanglement between the “BEC atoms” and the “photons” are numerically evaluated. It is shown that, the nonlinear interaction and other involved parameters in the presented model can dramatically affect the dynamics of the system. The collapse-revival phenomenon in the population inversion, Mandel parameter and atomic squeezing is a superb feature of the system which can be controlled by tuning the chosen parameters. Meanwhile, we propose an efficient way for the generation of sub-Poissonian and squeezed fields as well as squeezed atoms via nonlinear interaction of quantized filed with atomic BEC. In addition, it is found that, after the onset of interaction the system is always entangled. Altogether, under particular conditions, the approximated sudden death and then revival of entanglement can be observed.
关键词： Entanglement,Bose-Einstein condensate,Atomic population inversion,Atomic squeezing,Collapse-revival phenomenon
更新于2025-09-23 15:22:29
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Output field squeezing in a weakly-driven dissipative quantum Rabi model
摘要： We present a generalized method to address the squeezing spectrum of the output field for a weakly-driven, dissipative quantum Rabi model and calculate it for a range of coupling strengths covering strong, ultra-strong and deep-strong coupling regimes. The need for a generalization arises because of the periodic time dependence of the correlation functions due to counterrotating terms in the quantum Rabi model. We here adopt time-averaging over such correlation functions to obtain the squeezing spectrum, which may also be relevant to experimental situations. We compare the calculated squeezing spectra with those of the driven dissipative Jaynes-Cummings model to illustrate the departure from the latter as the interaction strength increases. Our calculation shows that the overall squeezing increases with the interaction strength after optimization over the system-bath coupling strength and the driving field strength.
关键词： Quantum Rabi model,Jaynes-Cummings model,Spectrum of squeezing
更新于2025-09-23 15:21:21
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Steady-State Spin Squeezing Generated in Diamond Nanostructures Coupled to Carbon Nanotubes
摘要： Spin squeezed state, as an important quantum resource, can be used to implement the high precise measurement beyond the standard quantum limit. Based on the recent novel scheme that strong magnetomechanical interaction between a single Nitrogen-vacancy (NV) spin and the vibrational mode of the suspended nanotube is engineered (Li et al. Phys. Rev. Lett. 117, 015502 2016), we investigate the steady-state spin squeezing behaviors of a spin ensemble in diamond coupled to carbon nanotubes by exerting a controllable microwave field. We show that steady-state spin squeezing can be generated with the help of the microwave field, despite the damping from mechanical damping. This investigation based on spin-spin interaction in diamond might apply to magnetometers, interferometry, and other precision measurement measurements.
关键词： External field,Spin squeezing,NV center
更新于2025-09-23 15:21:01
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Quantum Fluctuations in a Laser Soliton
摘要： The Heisenberg–Langevin equation for a spatial laser soliton is constructed within consistent quantum electrodynamics. Canonical variables for the generation field and for a two-level material medium consisting of a medium that generates a laser and a medium that realizes saturable absorption are discussed in detail. It is assumed that the laser generation evolves in time much more slowly than the atomic medium. This makes it possible to apply the adiabatic approximation and construct a closed equation for the amplitude of the laser field. The equation has been derived paying special attention to the definition of Langevin sources, which play a decisive role in the formation of quantum statistical features of solitons. To ensure the observation procedure of the quantum squeezing of a soliton, the laser generation has been synchronized by applying an external weak electromagnetic field.
关键词： Heisenberg–Langevin equation,quantum squeezing,laser soliton
更新于2025-09-23 15:21:01
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Quantum correlation and squeezing dynamics of a dissipative nonlinear optomechanical oscillator: Heisenberg-Langevin approach
摘要： In this paper, an optomechanical cavity that is quadratically coupled to the cavity ?eld and formed by a micropillar with Bragg re?ectors and a thin dielectric membrane, is studied. In addition, it is considered that this interaction occurs in the presence of Kerr medium, external laser ?eld and damping e?ects (for cavity ?eld and moving Bragg re?ector). Using the Heisenberg-Langevin approach, the dynamics of quantum correlation functions (for cavity ?eld and moveable re?ector) and squeezing parameters for quadratures of the cavity ?eld are investigated. In each case, the in?uences of optomechanical coupling, detuning parameter, thermal mean number of cavity photons and phonons, damping parameters and Kerr medium on the above nonclassicality features are analyzed in detail. It is illustrated that the amount of the above-mentioned physical phenomena can be controlled by appropriately choosing the evolved parameters. Also, we show that photon and phonon blockades emerge in some special cases.
关键词： squeezing dynamics,quantum correlation,photon blockade,optomechanical cavity,Kerr medium,Heisenberg-Langevin approach,phonon blockade
更新于2025-09-23 15:21:01
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Revealing Hidden Quantum Correlations in an Electromechanical Measurement
摘要： Under a strong quantum measurement, the motion of an oscillator is disturbed by the measurement backaction, as required by the Heisenberg uncertainty principle. When a mechanical oscillator is continuously monitored via an electromagnetic cavity, as in a cavity optomechanical measurement, the backaction is manifest by the shot noise of incoming photons that becomes imprinted onto the motion of the oscillator. Following the photons leaving the cavity, the correlations appear as squeezing of quantum noise in the emitted field. Here we observe such “ponderomotive” squeezing in the microwave domain using an electromechanical device made out of a superconducting resonator and a drumhead mechanical oscillator. Under a strong measurement, the emitted field develops complex-valued quantum correlations, which in general are not completely accessible by standard homodyne measurements. We recover these hidden correlations, using a phase-sensitive measurement scheme employing two local oscillators. The utilization of hidden correlations presents a step forward in the detection of weak forces, as it allows us to fully utilize the quantum noise reduction under the conditions of strong force sensitivity.
关键词： ponderomotive squeezing,microwave domain,electromechanical measurement,quantum correlations,hidden correlations
更新于2025-09-23 15:19:57
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Field Squeezing in a Quantum-Dot Molecule Jaynes-Cummings Model
摘要： We investigate the field squeezing in a system composed of an initial coherent field interacting with two quantum dots coupled by electron tunneling. An approximate quantum-dot molecule Jaynes-Cummings model describing the system is given, and the effects of physical quantities, such as the temperature, phonon-electron interaction, mean photon number, field detuning, and tunneling-level detuning, are discussed in detail.
关键词： Jaynes-Cummings model,phonon-electron interaction,electron tunneling,quantum-dot molecule,field squeezing
更新于2025-09-23 15:19:57
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Regulation of Optimal Entropy Squeezing Sudden Generation for a Moving Atomic Qubit Interacting with the Coherent Fields via Two-Photon Process
摘要： From the quantum information point of view, we investigate the regulation of optimal entropy squeezing sudden generation (OESSG) and disappearance (OESSD) for a moving atomic qubit interacting with the coherent field via two-photon process. It is shown that physical substance of atomic OESSG is entanglement sudden death of the atomic qubit and field, and atomic OESSD corresponds to the transient entanglement resurrection of atomic qubit and field. The duration, number component and stable cycle of the atomic OESSG can be controlled by choosing the initial atomic distribution angle ? and structure parameter p of the field mode, respectively. We realize the periodic exchange of atomic OESSG of components Sx and Sy, and also propose the exchange preparation scheme of atomic optimal entropy squeezing state. Our proposal may be useful for instantaneous control of quantum noise and retention of maximum coherent states of single atomic qubit in the noisy environment.
关键词： Optimal entropy squeezing sudden generation,Optimal entropy squeezing state,Field mode structure parameter,Moving atomic qubit
更新于2025-09-19 17:15:36