Two-mode Squeezed Vacuum Field Research Articles

Entangling the vibrational modes of two massive ferromagnetic spheres using cavity magnomechanics

We present a scheme to entangle the vibrational phonon modes of two massive ferromagnetic spheres in a dual-cavity magnomechanical system. In each cavity, a microwave cavity mode couples to a magnon mode (spin wave) via the magnetic dipole interaction, and the latter further couples to a deformation phonon mode of the ferromagnetic sphere via a nonlinear magnetostrictive interaction. We show that by directly driving the magnon mode with a red-detuned microwave field to activate the magnomechanical anti-Stokes process a cavity–magnon–phonon state-swap interaction can be realized. Therefore, if the two cavities are further driven by a two-mode squeezed vacuum field, the quantum correlation of the driving fields is successively transferred to the two magnon modes and subsequently to the two phonon modes, i.e., the two ferromagnetic spheres become remotely entangled. Our work demonstrates that cavity magnomechanical systems allow to prepare quantum entangled states at a more massive scale than currently possible with other schemes.

Polarization-based truncated SU(1,1) interferometer based on four-wave mixing in Rb vapor.

We propose and demonstrate a polarization-based truncated SU(1,1) interferometer that outputs the desired optical joint-quadrature of a two-mode squeezed vacuum field and allows its measurements using a single balanced homodyne detector. Using such a setup, we demonstrate up to ≈2dB of quantum noise suppression below the shot-noise limit in intensity-difference and phase-sum joint-quadratures, and confirm entanglement between the two quantum fields. Our proposed technique results in a better balance between the two ports of the detector and, consequently, in better common noise suppression for differential measurements. As a result, we are able to observe flat joint-quadrature squeezing and entanglement at a wide range of detection frequencies: from several MHz (limited by the photodiode gain bandwidth) down to a few hundred Hz (limited by electronic noises).

A Theoretical Scheme for Entanglement Transfer underIntensity-Dependent Couplings

We consider a theoretical scheme for entanglement transfer betweena two-mode squeezed vacuum field and two initially separable atomsthrough intensity-dependent couplings. We find that theentanglement transfer between the field and the atoms has an exactperiod for any given squeezing. We also find thatthe maximum achievable entanglement of the atomic subsystem is asimple increasing function of r. For sufficiently large squeezingparameter r, it is possible for the atoms to be entangled into aBell state at half the periodic time points.

Preparing entangled states of two atoms through the intensity-dependent interaction with the two-mode squeezed vacuum

Two four-level atoms resonantly interacting with a two-mode squeezed vacuum field through the intensity-dependent Jaynes–Cummings-like model are considered. It is shown that the atoms can evolve into pure entangled states at certain time. Moreover, the pure entangled states can probabilistically be projected onto extremely entangled states by quantum jump technique. It is shown that the success probability monotonously increases with increasing degree of squeezing without any decoherence processes. However, it is found that if decoherence processes such as atomic spontaneous emission and photon leakage out of the cavity take place, the total success probability first increases but then decreases with increasing degree of squeezing and finally approaches zero as the squeezing becomes stronger and stronger. Therefore, the high degree of squeezing in the initial state of the cavity field is not always helpful for a high probability of creating extremely entangled states when spontaneous emission and cavity decay exist. Given spontaneous emission and photon leakage rates, there is an optimal squeezing degree for which the total success probability becomes maximum.

Statistic properties of photon in the system of two coupling atoms interacting with two-mode squeezed vacuum field in Kerr medium

The statistic properties of photons in the system of two-mode squeezing vacuum field interacting with two coupling atoms in Kerr medium are studied by means of quantum theory.The influences of coupling constant χ, initial squeezed parameter r and the atomic initial state are discussed. The results obtained by means of numerical method show that the photon bunching and anti-bunching appear alternately, and the correlation of the two modes of light is both positive and non-classical. The periodical collapse-revival phenomenon of the time evolution of the second-order coherence degree of the two-mode field appears due to the influence of the Kerr effect. The periods of the collapse-revival become short up to disappearance with increasing Kerr effect.

Intermolecular-interaction effects on the quantum dynamics of dimers interacting with a two-mode squeezed vacuum field

We investigate the intermolecular-interaction effects on the quantum dynamics of dimer density matrices using several dimer models interacting with a two-mode squeezed vacuum field. It is found that the increase in the intermolecular interaction causes the resurrection of collapse-revival -like behaviors.

Intermolecular-interaction effects on quantum-phase dynamics of dimer systems interacting with a two-mode squeezed vacuum field

We investigate the intermolecular-interaction (dipole–dipole interaction) effects on the quantum dynamics of dimer density matrices and photon-phase distributions using several dimer models with different intermolecular distances in the presence of a two-mode squeezed vacuum field. In this photon field, each mode is initially correlated and the reduced one-mode photon distribution is equivalent with that of a thermal field. For comparison, we perform parallel studies, in which the initial fields are two types of noncorrelated two-mode fields, i.e., a two-mode coherent field and a two-mode thermal field. It is found that although the two-mode squeezed vacuum field causes the random oscillations of dimer populations in the noninteracting dimer, the periodic oscillations like the collapse–revival behavior emerge as the intermolecular distance decreases (the intermolecular interaction increases). Similar and dissimilar features among quantum dynamics caused by these three types of fields are investigated by analyzing the dynamical behavior of two-mode Pegg–Barnett photon-phase distributions and off-diagonal dimer density matrices, which indicate the coherency between dimer states. In addition to the quantum statistical properties of initial photon field, the change in the degree of contribution between one- and two-photon processes caused by the intermolecular interaction is found to be important to determine these features.

Quantum-phase dynamics of an atomic/molecular system interacting with a two-mode squeezed vacuum field: coexistence of quantum and thermal features

Abstract We investigate the dynamics of a three-state atomic/molecular model system interacting with a two-mode squeezed vacuum field in view of the correlation between the atomic/molecular density matrix and photon-phase distribution. It is found that two-mode squeezed vacuum field realizes the anomalous situation that the coherency between the atomic/molecular states concerning the two-photon process is preserved well during the dynamics though the coherency between other states completely vanish. This implies that the quantum and thermal features can coexist in the atomic/molecular system in the presence of two-mode squeezed vacuum field. Such phenomenon is found to originate in the feature of its initial photon-phase correlation of a two-mode squeezed vacuum. We also discuss how the present attractive features in off-diagonal density matrices affect the molecular non-linear polarization.

INFLUENCE OF A VIRTUAL PHOTON FIELD ON THE STATISTIC PROPERTIES OF PHOTONS IN A SYSTEM OF TWO-MODE SQUEEZED VACCUM FIELD INTERACTING WITH ATOMS

The statistic properties of photons in a system of two-mode squeezed vacuum field interacting with a two-level atom are studied without the rotating-wave approximation by means of quantum theory, and the influence of the virtual-photon process on the statistic properties of photons is discussed emphatically. The results obtained using a numerical method indicate that the influence of the virtual-photon process on the statistic properties of photons qives rise to quantum chaos, that is related to the initial state parameters of the system.

INFLUENCE OF THE VIRTUAL PHOTON FIELD ON THE ATOMIC QUANTUM CHARACTER IN TWO-MODE SQUEEZING VACUUM FIELD

We have investigated in the time-evolution and the squeezing character of atomic operators in a system of two-mode squeezed vacuum field interacting with a two-level atom without the rotating-wave approximation by means of quantum theory.The results obtained using the numerical method indicate that the influence of the virtual-photon field on the atomic quantum character is mainly the cause for quantum chaos which is related to the quantum character of the system itself.

ATOMIC DIPOLE SQUEEZING AND COHERENT POPULATION TRAPPING IN THE SYSTEM OF TWO-MODE SQUEEZED VACUUM FIELD INTERACTING WITH A TWO-LEVEL ATOM

The atomic quantum behaviors in the system of two-mode squeezed vacuum field interacting with a two-level atom via two-photon process are studied by means of quantum theory.The condition for the occurrence of coherent trapping and the influence of the squeezing parameters on the atomic dipole squeezing are discussed.

Aharonov-Bohm-Type Electron Interference in a Two-Mode Squeezed Vacuum Field

Electron interference related to Aharonov-Bohm effect in the presence of the two-mode quantized radiation field is investigated. Characteristics of the temporal behavior of electron interference are discussed. It is shown that for the two-mode squeezed vacuum field the time evolution of the intensity of electron interference can exhibit very interesting periodic spontaneous collapse and revival (CR). In addition, the relation between CR and the quantum fluctuation in electron interference is also discussed.

Detection of squeezed light by directional photoionization of coherently superposed states with different symmetries

We introduce a new approach to photodetection, based on absorbers (atoms, molecules, or dopant donors in semiconductors) that are kept in a steady superposition of two bound states having different spatial symmetries (e.g., s and p0). We consider the illumination of such absorbers by a superposition of two fields that are mutually orthogonal by virtue of polarization or frequency, and measurements of the resulting photocurrent along the direction of polarization of one of the fields. In contrast to conventional photon counters, the directional photocurrent generated in the considered scheme measures only the phase-sensitive cross products of the mutually orthogonal field amplitudes, without responding to the photon flux of each mode separately. If the light is a superposition of a one- or two-mode squeezed vacuum field and a nearly coherent (local-oscillator) field orthogonal to the former, then cross correlations between two such photocurrents yield the autocorrelation function of the squeezed-field quadrature without terms related to the noise of the local oscillator (although shot noise still affects the degree of accuracy to which the autocorrelation is measured).