Multimode States Research Articles

Optical field-strength generalized polarization of non-stationary quantum states in waveguiding photonic devices

A quantum analysis of the generalized polarization properties of multimode non-stationary states based on their optical field-strength probability distributions is presented. The quantum generalized polarization is understood as a significant confinement of the probability distribution along certain regions of a multidimensional optical field-strength space. The analysis is addressed to quantum states generated in multimode linear and nonlinear waveguiding (integrated) photonic devices, such as multimode waveguiding directional couplers and waveguiding parametric amplifiers, whose modes fulfill a spatial modal orthogonality. In particular, the generalized polarization degree of coherent, squeezed and Schrödinger’s cat states is analyzed.

Role of Vibrational Dynamics in Resonant Positron Annihilation on Molecules

Vibrational Feshbach resonances are dominant features of positron annihilation for incident positron energies in the range of the molecular vibrations. Studies in relatively small molecules are described that elucidate the role of intramolecular vibrational energy redistribution into near-resonant multimode states, and the subsequent coupling of these modes to the positron continuum, in suppressing or enhancing these resonances. The implications for annihilation in other molecular species, and the necessary ingredients of a more complete theory of resonant positron annihilation, are discussed.

Entanglement of quasi-symmetry multi-mode Gaussian states in continuous variable system

Entanglement of quasi-symmetry multi-mode Gaussian states in continuous variable system

多模准对称叠加态光场广义电场分量的高次振幅压缩

The light field state |ψ(5)(fj)〉q,a five states superposition multimode quantum functional superposition,that is formed by linearly superposing the multi-mode vacuum state |{0j}〉q and four generalized multimode functional coherent states |{f(m)j(x,y,z)}〉q(m=1,2,3,4) and the properties of the GN unequal-power higher-power Nj-power Y-S effects is further studied generally.The results indicate that ① the state |ψ(5)(fj)〉q is a general multimode nonclassical light field of five functional coherent states superposition,when the state |ψ(5)(fj)〉q is a unequal intensity quasi-symmetrical superposition,while some certain conditions are satisfied,the generalized electric field components of the state |ψ(5)(fj)〉q can display any unequal-power GN Nj-power amplitude squeezing effect.② the any quasi-symmetrical spatial distribution of the classical intensity and the classical amplitude,and the spatial arbitrary distribution characterization of the classical amplitude and the classical initial phase of light field in |ψ(5)(fj)〉q would have a direct influence upon the squeezing results and squeezing degree of the unequal-power amplitude squeezing effects presented by the state |ψ(5)(fj)〉q.

A limit formula for the quantum fidelity

Quantum fidelity is a central tool in quantum information, quantifying how much two quantum states are similar. By using the notion of generalized overlap, which occurs in the definition of the quantum Chernoff bound, we propose here a limit formula for the quantum fidelity between a mixed state and a pure state. As an example of an application, we apply this formula to the case of multimode Gaussian states, achieving a simple expression in terms of their first- and second-order statistical moments.

Invariant measures on multimode quantum Gaussian states

We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.

Realization of Single-Photon Frequency-Domain Qubit Channels Using Phase Modulators

In a recent paper, have developed a scheme for the stochastic implementation of arbitrary quantum operations on multimode single-photon qudit states by using reconfigurable linear-optic systems. Based on this idea, we explore the use of phase modulation for the realization of qubit channels in the frequency basis. Single-photon states belonging to two different frequency modes differing by the modulator's driving frequency represent the input dual-rail qubit states. The channel is implemented by a phase modulator followed by a fiber Bragg grating, taking advantage of the high degree of reconfigurability and microwave bandwidth shown by electrooptic modulation technology. The channels are realized by a combination of three techniques: 1) suitably designed driving waveforms, which are probabilistically addressed to the modulator; 2) the corresponding addressing probabilities; and 3) the grating transmittance at the values of the frequency basis. The proposed scheme results in nonoptimal success probabilities but is shown to allow for a compact implementation of the conventional qubit random unitary channels and the qubit amplitude-damping channel.

INTERFERENCE OF MULTI-MODE GAUSSIAN STATES AND "NON APPEARANCE" OF QUANTUM CORRELATIONS

We theoretically investigate bilinear, mode-mixing interactions involving two modes of uncorrelated multi-mode Gaussian states. In particular, we introduce the notion of "locally the same states" (LSS) and prove that two uncorrelated LSS modes are invariant under the mode mixing, i.e. the interaction does not lead to the birth of correlations between the outgoing modes. We also study the interference of orthogonally polarized Gaussian states by means of an interferometric scheme based on a beam splitter, rotators of polarization and polarization filters.

HIGH-ORDER PHOTON-NUMBER CORRELATIONS: A RESOURCE FOR CHARACTERIZATION AND APPLICATIONS OF QUANTUM STATES

We measure high-order correlation functions of detected-photon numbers in the mesoscopic regime by means of hybrid photodetectors. The analytical expressions for correlations are evaluated in terms of quantities that can be experimentally accessed by a selfconsistent analysis of the detectors' outputs. We demonstrate that high-order correlations can be used to characterize the nature of the optical states, for instance by better discriminating between classical and quantum behavior even in critical situations, such as multimode twin-beam state. The results are in very good agreement with the theory, both for classical states and quantum states.

Design on the Remote Heating Furnace Monitoring System Based on ZigBee Technology

For the hysteretic problems of using offline monitoring in traditional petrochemical corporations heating furnace, a design of realizing multimode heating furnace combustion state online monitoring system based on ZigBee technology is proposed. The system send the collected flue gas data to the PLC by the online flue gas analyzer, and send the flue gas data to configuration interface in the computer of control room for monitoring by the wireless network. The results of application show that the system is steady and reliable, and the data transmission is right and very stable and accord with the requirement desired.

Measuring Gaussian Quantum Information and Correlations Using the Rényi Entropy of Order 2

We demonstrate that the Rényi-2 entropy provides a natural measure of information for any multimode Gaussian state of quantum harmonic systems, operationally linked to the phase-space Shannon sampling entropy of the Wigner distribution of the state. We prove that, in the Gaussian scenario, such an entropy satisfies the strong subadditivity inequality, a key requirement for quantum information theory. This allows us to define and analyze measures of Gaussian entanglement and more general quantum correlations based on such an entropy, which are shown to satisfy relevant properties such as monogamy.

Discretely observable continuous-time quantum walks on Möbius strips and other exotic structures in three-dimensional integrated photonics

We theoretically analyze the dynamical evolution of photonic quantum walks on M\"obius strips and other exotic structures in 3D integrated photonics. Our flexible design allows discrete observations of continuous time quantum walks of photons in a variety of waveguide arrays. Furthermore, our design allows one to inject photons during the evolution, allowing the possibility of interacting with the photons as they are 'walking'. We find that non-trivial array topologies introduce novel time-dependent symmetries of the two-photon correlations. These properties allow a large degree of control for quantum state engineering of multimode entangled states in these devices.

Generation of nonlinear motional trio coherent states and their nonclassical properties

Using the nonlinear coherent states approach, a general formalism for the construction of various classes of nonlinear trio coherent states in the context of multi-mode quantum states has been proposed. In particular, taking into account the most popular nonlinearity function associated with f-deformed coherent states, i.e. the nonlinearity function of the centre-of-mass motion of a trapped ion, it is illustrated that the corresponding trio coherent state possesses some interesting nonclassical properties. To establish this observation, sub-Poissonian statistics, three-mode squeezing, the behaviour of Vogel's characteristic function and the existence of entanglement are investigated. Due to the intrinsic non-classicality nature of the considered three-mode states, their physical production may be of high interest in the quantum optics field. Thus, we have finally demonstrated how nonlinear motional trio coherent states can be generated in three-dimensional anisotropic traps, appropriately.

Quantum holographic teleportation of entangled two-color optical images

We introduce and theoretically investigate a scheme for teleportation of two-frequency entangled optical images in which the quantum channel is formed by four-frequency multimode states, generated in a single nonlinear photonic crystal by coupled parametric interactions. We study in detail the performance of the scheme. Namely, we evaluate its fidelity and the spatial-frequency spectra of the quadrature components characterizing the deterioration of the entanglement in the initial images due to the teleportation process. We analyze the influence of the spatial bandwidth of entanglement on the fidelity of teleportation. We investigate the performance of the scheme both in the near and the far diffraction field. Our analysis suggests that bandwidth matching of the quantum channel field with that of the images is generally necessary for high-quality teleportation. We show that entangled images are more fragile and more difficult to teleport than their coherent counterparts.

Measuring high-order photon-number correlations in experiments with multimode pulsed quantum states

We implement a direct detection scheme based on hybrid photodetectors to experimentally investigate high-order correlations for detected photons by means of quantities that can be experimentally accessed. We show their usefulness in fully characterizing a multimode twin-beam state in comparison with classical states and, in particular, we introduce a nonclassicality criterion based on a simple linear combination of high-order correlation functions. Our scheme is self-consistent, allowing the estimation of all the involved parameters (quantum efficiency, number of modes and average energy) directly from the same experimental data. Results are in very good agreement with theory, thus suggesting the exploitation of our scheme for reliable state characterization in quantum technology.

Two-mode superposition coherent states with spatial vortex structure for the quantized radiation field

Through superposing M two-mode coherent state a two-mode superposition coherent state with a spatial vortex structure in configuration space is constructed. Such quantum vortex state is an eigenstate of sum of squared two-mode annihilation operators and is always entangled. In the limiting condition of large M the quantum vortex state has a modified Bessel–Gaussian vortex structure with topological charge index n. Experimentally, such two-mode vortex states may be prepared by virtue of a multimode coherent state with currently available technology.

Ubiquitous Nature of Multimode Vibrational Resonances in Positron-Molecule Annihilation

Positron annihilation on many molecules occurs via positron capture into vibrational Feshbach resonances, with annihilation rates often further enhanced by energy transfer to vibrational excitations weakly coupled to the positron continuum. Data presented here uncover another scenario in which the positron couples directly to a quasicontinuum of multimode vibrational states. A model that assumes excitation and escape from a statistically complete ensemble of multimode vibrations is presented that reproduces key features of the data.

Gaussian matrix-product states for coding in bosonic communication channels

The communication capacity of Gaussian bosonic channels with memory has recently attracted much interest. Here, we investigate a method to prepare the multimode entangled input symbol states for encoding classical information into these channels. In particular, we study the usefulness of a Gaussian matrix product state (GMPS) as an input symbol state, which can be sequentially generated although it remains heavily entangled for an arbitrary number of modes. We show that the GMPS can achieve more than 99.9% of the Gaussian capacity for Gaussian bosonic memory channels with a Markovian or non-Markovian correlated noise model in a large range of noise correlation strengths. Furthermore, we present a noise class for which the GMPS is the exact optimal input symbol state of the corresponding channel. Since GMPS are ground states of particular quadratic Hamiltonians, our results suggest a possible link between the theory of quantum communication channels and quantum many-body physics.

Multimode polarization degree of mixture optical states in integrated directional couplers

Mixture multimode optical field classical states propagating in N × N integrated directional couplers are analyzed by using the density matrix formalism in a N-dimensional optical space. These mutimode optical fields present a kind of generalized polarization and accordingly a definition of a multimode polarization degree is proposed. It is based on the distance measure between a mixture state and an unpolarized state in a N-dimensional optical space so that in the case N=2 the standard polarization degree is recovered. It is shown that directional couplers can reduce or increase remarkably the multimode polarization degree of a mixture state. Likewise a simple measurement technique, based on Y junctions, of this multimode polarization degree is proposed. Finally all the results can be formally extended to the special case of multimode single photon quantum states.

Coherence collapse of the dual fiber Bragg grating external cavity semiconductor laser

The preconditions and controlling factors of coherence collapse (CC) are analyzed by the rate equations and dual fiber Bragg grating (FBG) couple mode theory based on the physical process of dual FBG external cavity semiconductor lasers. A method of achieving and controlling CC multi-mode stable state is put forward for dual FBG external cavity semiconductor lasers. When the dual FBG external cavity semiconductor laser operates at the multi-mode stable state under the CC regime, the CC length reduces. The spectrum of the laser is relatively stable within the CC length. The experimental results show the output power of the laser is stable while the laser with the 3% external reflectivity is operating under the CC regime. The side mode suppression ratio is more than 45 dB. The full wave at half maximum broadens from 0.5 nm to 0.9 nm dramatically as soon as the laser operates from the incoherence collapse regime to the CC regime. The wavelength shift is less than 0.5 nm at the operating temperature of 0 ℃70 ℃. The minimum of the CC length is less than 0.5 m. The CC application of dual FBG external cavity semiconductor lasers is vital to improve the performance of optical fiber amplifiers and fiber lasers.