Three-mode Entanglement Research Articles

Generation of Three-Mode Entanglement Based on Parametric Amplifiers Using Quantum Entanglement Swapping

Quantum entanglement swapping is one of the most promising quantum techniques to create or manipulate large-scale multi-mode entanglement between two distant quantum entangled systems. In this work, a scheme for the generation of three-mode entanglement based on parametric amplifiers using quantum entanglement swapping has been proposed. The newly generated three-mode entanglement is always present in the whole power gain region from parametric amplifiers and its dependence on transmission loss and feedforward gain is also investigated. In addition, the effects of power gain, transmission loss, and feedforward gain on the two-mode entanglement of the three pairs in the newly generated three-mode entanglement have also been analysed in detail. The results presented here may find some practical applications in quantum secure communication.

Multi-Mode Correlation in a Concurrent Parametric Amplifier

A concurrent parametric amplifier consisting of two pump beams is used to investigate the possibility of generating multi-mode correlation and entanglement. The existence of three-mode entanglement is demonstrated by analyzing the violation degree of three-mode entanglement criteria, including the sufficient criterion, i.e., two-condition and optimal single-condition criterion, and necessary and sufficient criterion, i.e., positivity under partial transposition (PPT) criterion. Besides, two-mode entanglement generated from any pair is also studied by using the Duan criterion and PPT criterion. We find that three-mode entanglement and two-mode entanglement of the two pairs are present in the whole parameter region. Our results pave the way for the realization and application of multi-mode correlation and entanglement based on the concurrent parametric amplifiers.

Higher-order Nonclassicality in Superposition of Three-mode Photon-added Trio Coherent State

In this paper, we study some higher-order nonclassical properties of the superposition of three-mode photon-added trio coherent state such as antibunching, squeezing, and entanglement. The results show that in the case with fixed the higher-order, when increasing the numbers of added photons, the manifestation of the higher-order three-mode sum squeezing is more obvious, but the degrees of higher-order antibunching, and higher-order three-mode entanglement are more reduced. Besides, with fixed the numbers of photon addition to the superposition of three-mode photon-added trio coherent state, the higher-order nonclassical properties as antibunching and entanglement are more pronounced, but three-mode sum squeezing is more decreased when increasing the number of the higher-order.

Deterministic Distribution of Multipartite Entanglement and Steering in a Quantum Network by Separable States.

As two valuable quantum resources, Einstein-Podolsky-Rosen entanglement and steering play important roles in quantum-enhanced communication protocols. Distributing such quantum resources among multiple remote users in a network is a crucial precondition underlying various quantum tasks. We experimentally demonstrate the deterministic distribution of two- and three-mode Gaussian entanglement and steering by transmitting separable states in a network consisting of a quantum server and multiple users. In our experiment, entangled states are not prepared solely by the quantum server, but are created among independent users during the distribution process. More specifically, the quantum server prepares separable squeezed states and applies classical displacements on them before spreading out, and users simply perform local beam-splitter operations and homodyne measurements after they receive separable states. We show that the distributed Gaussian entanglement and steerability are robust against channel loss. Furthermore, one-way Gaussian steering is achieved among users that is useful for further directional or highly asymmetric quantum information processing.

Higher-order nonclassical and entanglement properties in photon-added trio coherent state

This paper studies the higher-order nonclassical and entanglement properties in the photon-added trio coherent state (PATCS). We use the criterion of higher-order single-mode antibunching to evaluate the role of the photon addition operation. Furthermore, the general criteria for detection of higher-order three-mode sum squeezing and entanglement features in the PATCS are also investigated. The results show that the photon addition operation to a trio coherent state can enhance the degree of both the higher-order single-mode antibunching and the higher-order three-mode sum squeezing and enlarge the value of the higher-order three-mode entanglement factor in the photon-added trio coherent state. In addition, the manifestation of the single-mode antibunching and the entanglement properties are more obvious with increasing the higher values of orders.

HIGHER-ORDER NONCLASSICAL AND ENTANGLEMENT PROPERTIES IN PHOTON-ADDED TRIO COHERENT STATE

<p>This paper studies the higher-order nonclassical and entanglemet properties in the photon-added trio coherent state (PATCS). We use the criterion of higher-order single-mode antibunching to evaluate the role of photon addition operation. Moreover, the general criteria for detection of higher-order three-mode sum squeezing and entanglement features in the PATCS are also investigated. The results show that the photon addition operation to a trio coherent state can enhance the degree of both the higher-order single-mode antibunching and the higher-order three-mode sum squeezing, and enlarge the value of higher-order three-mode entanglement factor in the PATCS. In addition, the manifestation of the single-mode antibunching and the entanglement properties are more obvious with increasing the higher values of orders.</p>

Entanglement condition for W type multimode states and schemes for experimental realization

We derive a class of inequality relations, using both the sum uncertainty relations of su(2) algebra operators and the Schrodinger–Robertson uncertainty relation of partially transposed su(1,1) algebra operators, to detect the three-mode entanglement of non-Gaussian states of electromagnetic field. These operators are quadratic in mode creation and annihilation operators. The inseparability condition obtained using su(2) algebra operators is shown to guarantee the violation of Schrodinger–Robertson uncertainty relation of partially transposed su(1,1) algebra operators. The obtained inseparability condition incorporates all the required bipartite entanglement conditions to detect the W type three-mode entangled states and hence it is shown to be a necessary condition for W type three-mode entangled states. A general form for a family of such inseparability conditions is provided. The results derived for three-mode systems are generalized to multimode systems. Experimental schemes using symmetric multiport beam splitters and multi-Λ EIT system are proposed to test the violation of multimode separability condition.

Two- and three-mode dressed entanglement multichannel in cavity four-wave mixing of Pr3+: YSO

We report a theoretical study into the two- and three-mode entanglement inside an atom-like optical cavity. A five-level system is considered and the influence of the multi-dressed parametric amplification four-wave mixing (PA-FWM) process on the quantum correlation of fluctuation spectra is researched. Three-mode entanglement is determined by the coupling of two nonlinear gains; one of enhanced gains via the dressing state plays a dominant role in controlling and optimizing the profile of three-mode entanglement via vacuum Rabi splitting, enhancement/suppression of entanglement as well as two-mode. Specifically, increasing the quantity of dressing fields may result in the single-channel entanglement turning into nonlocal multichannel (multiple anti-crossing behaviors). Moreover, these entanglement channels can be squashed via the lateral squeezing effect of the cavity. Such multichannel entanglement has potential applications in nonlocal quantum imaging and quantum key distribution.

Generation of tripartite entanglement from cascaded four-wave mixing processes.

We investigate the possibility of an experimentally feasible cascaded four-wave mixing (FWM) system [Phys. Rev. Lett. 113, 023602 (2014)] to generate tripartite entanglement. We verify that genuine tripartite entanglement is present in this system by calculating the covariances of three output beams and then considering the violations of the inequalities of the three-mode entanglement criteria, such as two-condition criterion, single-condition criterion, optimal single-condition criterion and the positivity under partial transposition (PPT) criterion. We also consider the possibilities of the bipartite entanglement of any pair of the three output beams using the Duan-Giedke-Cirac-Zoller criterion and PPT criterion. We find that the tripartite entanglement and the bipartite entanglement for the two pairs are present in the whole gain region. The entanglement characteristics under different entanglement criteria are also considered. Our results pave the way for the realization and application of multipartite entanglement based on the cascaded FWM processes.

Dressing control of three-mode entanglement in two cascaded four-wave mixing

We report the control of the dressed state in three-mode optical entanglement in an N-type four-level system using two cascaded parametric amplification four-wave mixing steps inside an atom-like optical cavity and injected by thermal optical fields: a coherent field and the Einstein–Podolsky–Rosen field. First, cavity dressing results in Aulter–Towns-like (AT-like peak) anti-squeezing. And the three-cavity dressing interaction induces multi-AT-like peaks. Meanwhile, the cavity enhanced nonlinear gain results in one squeezing dip polariton. In addition, the coupling of three enhanced nonlinear gains brings about multi-dip squeezing. Second, as two nonlinear coefficients change, the nonlinear phase makes the squeezing profile (in phase, amplification) turn into an anti-squeezing profile due to nonlinear loss (out of phase, de-amplification). Finally, the squeezing profile can also be modified by field dressing (AT splitting, enhancement and suppression), and the squeezing degree is affected by injection fields. Thus, by judging the squeezing of three nonseparability criteria, we get three-mode optical entanglement.

Entangling the Whole by Beam Splitting a Part

A beam splitter is a basic linear optical element appearing in many optics experiments and is frequently used as a continuous-variable entangler transforming a pair of input modes from a separable Gaussian state into an entangled state. However, a beam splitter is a passive operation that can create entanglement from Gaussian states only under certain conditions. One such condition is that the input light is suitably squeezed. We demonstrate, experimentally, that a beam splitter can create entanglement even from modes which do not possess such a squeezing provided that they are correlated to, but not entangled with, a third mode. Specifically, we show that a beam splitter can create three-mode entanglement by acting on two modes of a three-mode fully separable Gaussian state without entangling the two modes themselves. This beam splitter property is a key mechanism behind the performance of the protocol for entanglement distribution by separable states. Moreover, the property also finds application in collaborative quantum dense coding in which decoding of transmitted information is assisted by interference with a mode of the collaborating party.

Quantum correlations and energy currents across three dissipative oscillators

We present a study that addresses both the stationary properties of the energy current and quantum correlations in a three-mode chain subjected to Ohmic and super-Ohmic dissipations. An extensive numerical analysis shows that the mean value and the fluctuations of the energy current remain insensitive to the emergence of a rich variety of quantum correlations, such as two-mode discord and entanglement and bipartite three-mode and genuine tripartite entanglement. The discussion of the numerical results is based on the derived expressions for the stationary properties in terms of the two-time correlation functions of the oscillator operators, which carry the quantum correlations. Interestingly, we show that quantum discord can be enhanced by considering both initially squeezed thermal bath states and imposing temperature gradients.

Creating three-mode entanglement of optical fields via effective coupling to separated atomic ensembles

We present a scheme to generate three-mode entanglement of optical fields based on concurrent interaction with separated atomic ensembles. The inseparability criterion for multimode entanglement [Phys. Rev. A 67 (2003) 052315] is well satisfied in a wide range of relevant parameters, which is sufficient to demonstrate genuine tripartite entanglement. Unlike most of the proposals that the environment will induce decoherence, here we show that the largest correlations of the three cavity modes are insensitive to the cavity decay rate. It is also found that the best correlations can be optimized by the effective coupling constants between the cavity fields and the collective atomic operators.

Output three-mode entanglement via coherently prepared inverted Y-type atoms

In this paper, the output quantum correlations of three fields interacting with inverted Y-type atoms inside a three-mode cavity are investigated. By numerically calculating the stationary noise spectra of the fields, we show that it is possible to generate the genuine tripartite continuous variable entanglement outside the cavity by coherently preparing the atoms in a superposition of the upper excited state and two ground states initially. Our numerical results demonstrate that both zero frequency entanglement and sideband frequency entanglement can be obtained under different initial coherent conditions. In addition, we investigate the thermal fluctuation effects on the quantum entanglement. It is found out that the entanglement occurring in a high frequency regime is more robust against thermal noise than the zero frequency entanglement, which may be useful for quantum communication.

Generation of Enhanced Three-Mode Continuously Variable Entanglement

The generation of enhanced three-mode continuously variable (CV) entanglement via difference-frequency amplification in an optical cavity above the threshold is investigated. The quantum entanglement characteristics among the pump, signal, and idler beams are demonstrated by applying a sufficient inseparability criterion for CV entanglement proposed by van Loock and Furusawa. Bright three-mode CV entanglement with different frequencies can be generated in this simple system when the optical cavity operates above its threshold, and the best three-mode CV entanglement can be obtained when the pump threshold parameter is modulated at about σ = 1.3.

Bright three-color continuous-variable entanglement generated by a cascaded sum-frequency process in an optical cavity

Bright three-color continuous-variable (CV) entanglement generated by a cascaded sum-frequency process in an optical cavity is investigated. The second- and fourth-harmonic beams can be generated by two quasi-phase-matched cascaded sum-frequency processes in a quasi-periodic optical superlattice. Quantum correlations among the fundamental and second- and fourth-harmonic beams are calculated and discussed by applying a sufficient and necessary inseparability criterion for CV three-mode entanglement. Strong three-color CV entanglement beams with a double frequency interval can be produced in this simple system. It is experimentally feasible and may be very useful for applications in quantum communication and computation networks.

Generation of three-mode light entanglement via double-channel resonant four-wave mixing

We present a scheme to generate tripartite continuous-variable entanglement at the steady state by using an ensemble of N a five-level double- Λ − V atoms embedded in a three-mode cavity. The scheme is based on the two-channel resonant four-wave mixing, which leads to the parametric interaction between the sum mode of two fields from the upper double- Λ system and the mode from the lower V system. It is for such reason that three cavity modes are correlated and entangled. The present scheme has the following two striking features. One is that the steady-state tripartite entanglement is achieved under the full-resonance condition. Another feature is the fact that all the fields are coupled to the different atomic transitions, respectively. In particular, the tripartite entanglement occurs among the fields with the large frequency differences, which may be necessary for the progress of quantum information.

Quantum coherence and correlations of optical radiation by atomic ensembles interacting with a two-level atom in a microwave cavity

We examine quantum statistics of optical photons emitted from atomic ensembles which are classically driven and simultaneously coupled to a two-level atom via microwave photon exchange. Quantum statistics and correlations are analyzed by calculating second-order coherence degree, von Neumann entropy, spin squeezing for multiparticle entanglement, as well as genuine two- and three-mode entanglement parameters for steady-state and nonequilibrium situations. Coherent transfer of population between the radiation modes and quantum-state mapping between the two-level atom and the optical modes are discussed. A potential experimental realization of the theoretical results in a superconducting coplanar waveguide resonator containing diamond crystals with nitrogen-vacancy color centers and a superconducting artificial two-level atom is discussed.

Scheme to generate three-mode continuous-variable entanglement in cavity quantum electrodynamics

We propose a theoretical method of generating a three-mode continuous-variable entanglement in an optical cavity with an atomic cloud. The scheme uses Raman transitions between stable atomic ground states and under the input–output theory a three-mode entangled light of the output fields can be produced. The characters of the tripartite entanglement, the degree of the quadrature-phase amplitude correlations among the three modes are discussed by applying a sufficient inseparability criterion for multipartite continuous-variable entanglement, which was proposed by van Loock and Furusawa. The dependences of the correlation on the effective coupling constants are theoretically analyzed.

Two Methods to Dynamics of Cavityless Optomechanical Systems

We present two methods to solve the equation of motion of the cavityless optomechanical system and obtain an explicit formula of the covariance matrix of the evolved state when the initial state is Gaussian. We study the entanglement dynamics of this system initially in the vacuum state. It is shown that bipartite entanglement behaves in a periodic manner. In particular, we can easily generate a genuine three-mode continuous-variable entanglement.