Detecting nonclassicality and non-Gaussianity by the Wigner function and quantum teleportation in photon-added-and-subtracted two modes pair coherent state
Abstract We introduce a new state called photon-added-and-subtracted two modes pair coherent state (PAASTMPCS) by simultaneously adding and subtracting photons to the different modes of a pair coherent state. Its nonclassical and non-Gaussian properties are strengthened via the negative values of its Wigner function as the numbers of adding and subtracting photons are increased. It indicates that the PAASTMPCS is an entangled state. When increasing the numbers of photon-added and photon-subtracted to a pair coherent state, the degree of entanglement in the PAASTMPCS is enhanced compared with the original pair coherent state. By using a PAASTMPCS as a non-Gaussian entangled resource, the quantum teleportation processes are studied in detail. It is shown that the number sum and phase difference measurements protocol is more appropriate than the orthogonal quadrature components measurements protocol in the quantum teleportation process of a coherent state.
Abstract We introduce a new state called photon-added-and-subtracted two modes pair coherent state (PAASTMPCS) by simultaneously adding and subtracting photons to the different modes of a pair coherent state. Its nonclassical and non-Gaussian properties are strengthened via the negative values of its Wigner function as the numbers of adding and subtracting photons are increased. It indicates that the PAASTMPCS is an entangled state. When increasing the numbers of photon-added and photon-subtracted to a pair coherent state, the degree of entanglement in the PAASTMPCS is enhanced compared with the original pair coherent state. By using a PAASTMPCS as a non-Gaussian entangled resource, the quantum teleportation processes are studied in detail. It is shown that the number sum and phase difference measurements protocol is more appropriate than the orthogonal quadrature components measurements protocol in the quantum teleportation process of a coherent state.
Abstract Pair coherent states (PCSs) as a kind of two-mode non-Gaussian and nonclassical states were introduced and studied. Some nonclassical characteristics of them such as two-mode sum-squeezing, two-mode antibunching, and entanglement have been well investigated. In this paper, we focus on studying the superposition of photon addition and subtraction to the PCSs called superposition of photon-added and photon-subtracted pair coherent states (SPAPSPCSs). Our main purpose is to show that the non-Gaussian feature and all the above-mentioned nonclassical properties of the SPAPSPCSs can be enhanced compared with the photon-added-and-subtracted two modes pair coherent states (PAASTMPCSs) and the original PCSs. In general, we demonstrate that the SPAPSPCSs have more enhanced non-Gaussian character and nonclassical properties than the PCSs and the PAASTMPCSs by examining the negativity of the Wigner function. Specifically, we indicate that both the SPAPSPCSs and the PAASTMPCSs can exist in two-mode sum-squeezing while the original PCSs (without photon-addition and photon-subtraction) cannot, and the degree of squeezing is stronger in the SPAPSPCSs than in the PAASTMPCSs. The obtained results also indicate that the superposition of photon addition and subtraction of the SPAPSPCSs plays a vital role in enhancing the two-mode antibunching property and the entanglement degree compared with the PCSs and the PAASTMPCSs.
Abstract A study of non-Gaussian operations in a single/two-mode quantum state is of great importance because of the enhancement of non-classicality. Experimental evidence of the generation of a Pair Coherent State (PCS) and the feasibility of non-Gaussian operations using beam splitters and nonlinear crystals motivated us to study non-Gaussian PCS. Recently, we studied various nonclassicality criteria in a particular case of non-Gaussian PCS. Here, we explore different combinations of photon addition/subtraction in either mode of PCS. For example, we studied photon addition and subtraction (PAS), photon subtraction and addition (PSA), photon addition and addition (PAA), and photon subtraction and subtraction (PSS) in two modes of PCS. We present a quantitative measure of nonclassicality in the form of inequality known as Klyshko’s criterion for the different combinations of PCS to show the nonclassical behavior of the states quantitatively. Here, we also present the corresponding coefficients (C n ) for each different case of PCS and analyze the effect of photon addition and subtraction on the photon-number distribution, linear entropy, single-photon source efficiency (SPS), Q-function, and fidelity for quantum teleportation. We illustrate our results through numerical simulations and compare them with standard PCS. We observe the changes induced by different combinations in PCS, leading to enhanced nonclassicality. Our results show that the PSA and PSS configurations demonstrate the strongest Klyshko nonclassicality, while the PAA state exhibits maximal entanglement via linear entropy and strong efficiency. In particular, the PAS state achieves the highest teleportation fidelity (F > 0.88). These findings establish photon-added/subtracted PCS as practical and tunable resources for quantum communication and metrology tasks.
Abstract In this paper, we aim to introduce a new state called photon-subtracted-then-added squeezing-enhanced coherent state (PSASECS) by multiple photon subtraction and then addition to a squeezing-enhanced coherent state. We investigate the non-Gaussianity and nonclassicality of this new state in detail, including its Wigner function, sub-Poissonian statistics, Q -function, squeezing, and antibunching properties. The obtained results indicate that these non-Gaussian and nonclassical characteristics have been enhanced by appropriately changing between photon subtraction l and photon addition k . Additionally, the non-Gaussianity and nonclassicality of PSASECS are enhanced compared to cases involving only the addition or subtraction of photons. This demonstrates the importance of subtracting and then adding photons to the squeezing-enhanced coherent state, and introducing a significant state for application in quantum optics, particularly in mitigating phase noise fluctuations in quantum devices.
In this paper, we study the nonclassical properties and find out the effect of photon addition on these properties as well as the process of teleportation in the two-mode photon-added displaced squeezed (TMPADS) states. We derive the analytic expressions of the Wigner function, the photon number distribution and the intermode photon antibunching for these states. We show that photon addition operation not only makes the Wigner function become negative but also leads to increase the degree of antibunching. The peak of the photon number distribution becomes flatter and shifts to the greater number of photons by adding photons to both modes simultaneously. Furthermore, it is proved that the degree of intermodal entanglement becomes bigger and bigger through increasing the number of photons added to both modes. As expected, when using these states as an entanglement resource to teleport a state, the average fidelity of teleportation process is also improved by increasing the number of added photons.
Abstract The coherent photon-subtracted two-mode squeezed thermal states (CPS-TMSTS) are theoretically introduced by successively performing coherent photon subtraction operation on the two-mode squeezed thermal states (TMSTS). Based upon the normalization factor which is related to bivariate Hermite polynomials, the nonclassicality and non-Gaussianity are analyzed according to the Wigner function. It is shown that the coherent photon subtraction operation is an effective manner in generating nonclassicality and non-Gaussianity. Furthermore, the fidelity in teleporting coherent states using CPS-TMSTS as entangled resources is quantified both analytically and numerically. It is shown that the quantities of fidelity are clearly larger than that in the original TMSTS, and it can be further improved by modulating control parameters effectively. The CPS-TMSTS, as the ideal entangled resources with higher quantum teleportation fidelity, shall have potential applications in quantum optics tasks.
In continuous-variable quantum information, non-Gaussian entangled states that are obtained from Gaussian entangled states via photon subtraction are known to contain more entanglement. This makes them better resources for quantum information processing protocols, such as, quantum teleportation. We discuss the teleportation of non-Gaussian, non-classical Schrödinger-cat states of light using two-mode squeezed vacuum light that is made non-Gaussian via subtraction of a photon from each of the two modes. We consider the experimentally realizable cat states produced by subtracting a photon from the single-mode squeezed vacuum state. We discuss two figures of merit for the teleportation process, (a) the fidelity, and (b) the maximum negativity of the Wigner function at the output. We elucidate how the non-Gaussian entangled resource lowers the requirements on the amount of squeezing necessary to achieve any given fidelity of teleportation, or to achieve negative values of the Wigner function at the output.