Higher-order Nonclassical Properties Research Articles

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.

Lower- versus higher-order nonclassicalities for a coherent superposed quantum state

A coherent state is defined conventionally in different ways such as a displaced vacuum state, an eigenket of an annihilation operator, or as an infinite dimensional Poissonian superposition of Fock states. In this work, we describe a superposition ( t a + r a † ) of field annihilation and creation operators acting on a continuous variable coherent state | α ⟩ and specify it by | ψ ⟩ . We analyze the lower- as well as higher-order nonclassical properties of | ψ ⟩ . The comparison is performed by using a set of nonclassicality witnesses (e.g., higher-order photon statistics, higher-order antibunching, higher-order sub-Poissonian statistics, higher-order squeezing, Agarwal–Tara parameter, Klyshko’s condition, and a relatively new concept, matrix of phase-space distribution). It is found that the higher-order criteria are much more efficient to detect the presence of nonclassicality as compared to lower-order conditions except squeezing, where the lower-order one is more competent than its higher-order counterpart.

A comparison between higher-order nonclassicalities of superposition engineered coherent and thermal states

We consider an experimentally obtainable superposition (SUP) operator, defined by using a generalized superposition of products of field annihilation (a) and creation (a†) operators of the type A = saa† + ta†a with s2 + t2 = 1. We apply this SUP operator on coherent and thermal quantum states, and the states thus produced are referred to as SUP-operated coherent state (SOCS) and SUP-operated thermal state (SOTS), respectively. In the present work, we report a comparative study between the higher-order nonclassical properties of SOCS and SOTS. The comparison is performed by using a set of nonclassicality witnesses (e.g., higher-order anti-bunching, higher-order sub-Poissonian photon statistics, higher-order squeezing, Agarwal–Tara parameter, Klyshko’s condition). The existence of higher-order nonclassicalities in SOCS and SOTS have been investigated for the first time. In view of possible experimental verification of the proposed scheme, we present exact calculations to reveal the effect of non-unit quantum efficiency of quantum detector on higher-order nonclassicalities.

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>

Higher-order nonclassical properties of nonlinear charge pair cat states

The concept of nonlinear charge pair cat states is introduced and their higher-order nonclassical properties are studied. By comparing the nonlinear cases of photon-added states f2(n) and a laser-driven trapped ion f3(n) with the linear case f1(n), it is shown that these states exhibit two-mode higher-order antibunching to all orders and the degree of antibunching depends on the suitable variables, especially on the nonlinear functions. We also show that in such states, the higher-order squeezing appears only in the even orders and the squeezing behaviours for the nonlinear cases f2(n) and f3(n) are quite opposite. These states are two-mode genuinely entangled regardless of the nonlinear functions and their entanglement properties are more obvious in the photon-added states f2(n) case.

Generalized binomial state: Nonclassical features observed through various witnesses and a quantifier of nonclassicality

Experimental realization of various quantum states of interest has become possible in the recent past due to the rapid developments in the field of quantum state engineering. Nonclassical properties of such states have led to various exciting applications, specifically in the area of quantum information processing. The present article aims to study lower- and higher-order nonclassical features of such an engineered quantum state (a generalized binomial state based on Abel’s formula). Present study has revealed that the state studied here is highly nonclassical. Specifically, higher-order nonclassical properties of this state are reported using a set of witnesses, like higher-order antibunching, higher-order sub-Poissonian photon statistics, higher-order squeezing (both Hong–Mandel type and Hillery type). A set of other witnesses for lower- and higher-order nonclassicality (e.g., Vogel’s criterion and Agarwal’s A parameter) have also been explored. Further, an analytic expression for the Wigner function of the generalized binomial state is reported and the same is used to witness nonclassicality and to quantify the amount of nonclassicality present in the system by computing the nonclassical volume (volume of the negative part of the Wigner function). Optical tomogram of the generalized binomial state is also computed for various conditions as Wigner function cannot be measured directly in an experiment in general, but the same can be obtained from the optical tomogram with the help of Radon transform.

Higher-Order Nonclassical Properties of a Shifted Symmetric Cat State and a One-Dimensional Continuous Superposition of Coherent States

Role of quantum interference in the origin of higher-order nonclassical characteristics of radiation field has been probed vis-a-vis a discrete and a continuous superposition of coherent states. Specifically, the possibilities of observing higher-order nonclassical properties (e.g., higher-order antibunching (HOA), higher-order sub-Poissonian photon statistics (HOSPS), higher-order squeezing (HOS) of Hong-Mandel type and Hillery type) have been investigated using a shifted symmetric cat state that reduces to Yurke-Stoler, even and odd coherent states at various limits. This shifted symmetric cat state which can be viewed as a discrete superposition of coherent states is found to show HOA and HOSPS. Similarly, higher-order nonclassical properties of a one-dimensional continuous superposition of coherent states is also studied here. The investigation has revealed the existence of HOS and HOSPS in the one-dimensional continuous superposition of coherent states studied here. Effect of non-Gaussianity inducing operations (e.g., photon addition and addition followed by subtraction) on these superposition states have also been investigated. Finally, some comparisons have been made between the higher-order nonclassical properties of discrete and continuous superposition of coherent states.

Higher-order nonclassicalities of finite dimensional coherent states: A comparative study

Conventional coherent states (CSs) are defined in various ways. For example, CS is defined as an infinite Poissonian expansion in Fock states, as displaced vacuum state, or as an eigenket of annihilation operator. In the infinite dimensional Hilbert space, these definitions are equivalent. However, these definitions are not equivalent for the finite dimensional systems. In this work, we present a comparative description of the lower- and higher-order nonclassical properties of the finite dimensional CSs which are also referred to as qudit CSs (QCSs). For the comparison, nonclassical properties of two types of QCSs are used: (i) nonlinear QCS produced by applying a truncated displacement operator on the vacuum and (ii) linear QCS produced by the Poissonian expansion in Fock states of the CS truncated at (d−1)-photon Fock state. The comparison is performed using a set of nonclassicality witnesses (e.g., higher order antibunching, higher order sub-Poissonian statistics, higher order squeezing, Agarwal–Tara parameter, Klyshko's criterion) and a set of quantitative measures of nonclassicality (e.g., negativity potential, concurrence potential and anticlassicality). The higher order nonclassicality witnesses have found to reveal the existence of higher order nonclassical properties of QCS for the first time.

Even and Odd Charge Coherent States: Higher-Order Nonclassical Properties and Generation Scheme

We examine the higher-order nonclassical properties of the even and odd charge coherent states as well as proposing a scheme to generate these states whose modes can freely travel in open space. We show that the even and odd charge coherent states exhibit both higher-order antibunching and higher-order squeezing. While the two-mode higher-order antibunching occurs in any order and essentially depends on the charge number, the two-mode higher-order squeezing appears only in the even orders. We also prove that these states are genuinely entangled, and they can be generated by means of cross-Kerr media, beam splitters, phase shifts and threshold detectors. We find that the fidelity and the corresponding success probability to generate these states are dependent on the correlative parameters.

Higher-Orders of Squeezing, Sub-Poissonian Statistics and Anti-Bunching of Deformed Photon-Added Coherent States

In this paper, we investigate the higher-order nonclassical properties of a particular class of generalized coherent states namely the deformed photon-added nonlinear coherent states (DPACS) A†m |α, f, m〉. To achieve this purpose we pay attention to higher-orders of squeezing (both Hillery- and Hong–Mandel-types), sub-Poissonian statistics and anti-bunching of the mentioned states with a well-known nonlinearity function. It is shown that for enough large values of field intensity (|α|2) for a fixed N (the order of squeezing) by increasing m (the order of excitation) the degree of squeezing evaluated by Hillery and Hong–Mandel approaches increases, while for a chosen fixed value of m, by increasing N for Hillery (Hong–Mandel) type of squeezing the strength of squeezing decreases (increases). Similarly, the degree of higher-order sub-Poissonian statistics (with fixed K) becomes lower when m increases, while (with fixed m) it gets greater values when the order of sub-Poissonian K increases. At last, higher-order anti-bunching of the DPACS is evaluated, by which we established that its (always) negative values increase with increasing m, α and l (the order of anti-bunching) individually, i.e. the degree of anti-bunching increases.

Higher nonclassical properties and entanglement of photon-added two-mode squeezed coherent states

We investigate how photon addition operations affect some higher-order nonclassical properties and the intermodal entanglement of a non-Gaussian entangled state generated by adding photons to both modes of a two-mode squeezed coherent state (TMSCS). We show that the photon addition operation can enhance the degrees of the sum squeezing and the difference squeezing for appropriate combinations of several parameters involved in the TMSCS. We consider the existing Hillery-Zubairy entanglement criterion, and find that the quantity of Hillery-Zubairy E gets more negative not only for a larger value of the squeezing parameter r but also for greater values of photon addition numbers (m, n). Our results may imply that the highest enhancement is obtained when same number of operations (i.e., m=n) is applied to both modes. However, for the photon-added TMSCS (PA-TMSCS), the more violation to the Hillery-Zubairy inequality does not necessarily following strong sum squeezing and difference squeezing. This because their behaviors with three phases and squeezing parameter r involved in the TMSCS are somewhat different.

Sum Squeezing, Difference Squeezing, Higher-Order Antibunching and Entanglement of Two-Mode Photon-Added Displaced Squeezed States

In this paper, we study some higher-order nonclassical properties and intermodal entanglement that may arise in the so called two-mode photon-added displaced squeezed state. We derive analytical expressions for the degree of sum squeezing and difference squeezing, which are interesting kinds of two-mode squeezing, as well as for the degree of antibunching to any orders. We also examine the degree of entanglement between the two modes using the existing Hillery-Zubairy criterion. Based on the derived expressions we analyze in detail the behavior of these nonclassical effects and entanglement depending on the parameters involved.