Fidelity Of Teleportation Research Articles

Entanglement Teleportation of a Two-Qubit System via Correlated Quantum Channels

We address the teleportation of a two-qubit entangled state through quantum channels where successive uses of the channels are correlated, and investigate how memory effect induced by successive uses of the channels influences the entanglement teleportation and fidelity. The analytical expressions of the entanglement teleportation and average fidelity under three different correlated channels are presented. Our results show that, the output entanglement teleportation strongly depends on the source state, the initial entanglement of teleporting state and parameters of noisy channels. However, the average fidelity is only affected by the parameters of the source state and noisy channels.

Tripartite non-maximally-entangled mixed states as a resource for optimally controlled quantum teleportation fidelity

Three-qubit mixed states are used as a channel for controlled quantum teleportation (CQT) of single-qubit states. The connection between different channel parameters to achieve maximum controlled teleportation fidelity is investigated. We show that for a given multipartite entanglement and mixedness, a class of non-maximally entangled mixed $X$ states ($X-$NMEMS) achieves optimum controlled quantum teleportation fidelity, interestingly a class of maximally entangled mixed $X$ states ($X-$MEMS) fails to do so. This demonstrates, for a given spectrum and mixedness, that $X-$MEMS are not sufficient to attain optimum controlled quantum teleportation fidelity, which is in contradiction with the traditional quantum teleportation of single qubits. In addition, we show that biseparable $X-$NMEMS, for a certain range of mixedness, are useful as a resource to attain high controlled quantum teleportation fidelity, which essentially lowers the requirements of quantum channels for CQT.

Spin chains for two-qubit teleportation

Generating high-quality multi-particle entanglement between communicating parties is the primary resource in quantum teleportation protocols. To this aim, we show that the natural dynamics of a single spin chain is able to sustain the generation of two pairs of Bell states - possibly shared between a sender and a distant receiver - which can in turn enable two-qubit teleportation. In particular, we address a spin-1/2 chain with XX interactions, connecting two pairs of spins located at its boundaries, playing the roles of sender and receiver. In the regime where both end pairs are weakly coupled to the spin chain, it is possible to generate at predefinite times a state that has vanishing infidelity with the product state of two Bell pairs, thereby providing nearly unit fidelity of teleportation. We also derive an effective Hamiltonian via a second-order perturbation approach that faithfully reproduces the dynamics of the full system.

Quantum teleportation through atmospheric channels

We study the Kimble–Braunstein continuous-variable quantum teleportation with the quantum channel physically realized in the turbulent atmosphere. In this context, we examine the applicability of different strategies preserving the Gaussian entanglement (Bohmann et al 2016 Phys. Rev. A 94 010302(R)) for improving the fidelity of the coherent-state teleportation. First, we demonstrate that increasing the squeezing parameter characterizing the entangled state is restricted by its optimal value, which we derive for realistic experimentally-verified examples. Further, we consider the technique of adaptive correlations of losses and show its performance for channels with large squeezing parameters. Finally, we investigate the efficiencies of postselection strategies in dependence on the stochastic properties of the channel transmittance.

Teleportation improvement by noiseless linear amplification

We address de-Gaussification of continuous variables Gaussian states by optimal non-deterministic noiseless linear amplifier (NLA) and analyze in details the properties of the amplified states. In particular, we investigate the entanglement content and the non-Gaussian character for the class of non-Gaussian entangled state obtained by using NL-amplification of two-mode squeezed vacua (twin-beam, TWB). We show that entanglement always increases, whereas improved EPR correlations are observed only when the input TWB has low energy. We then examine a Braunstein-Kimble-like protocol for the teleportation of coherent states, and compare the performances of TWB-based teleprotation with those obtained using NL-amplified resources. We show that teleportation fidelity and security may be improved for a large range of NLA parameters (gain and threshold).

Quantum Teleportation under Different Local Independent Noise Environment

We study the average fidelity of the standard quantum teleportation when the quantum channel is subjected to different local independent noise environments frequently encountered in real quantum communication protocol. We show that only $$ \left|{\mathrm{Bell}}_1\right\rangle =\frac{1}{\sqrt{2}}\left(\left|00\right\rangle +\left|11\right\rangle \right) $$ is the best quantum channel in different independent noise environments, even in the depolaring noise environment. Our work can shed some light on the application of practical standard quantum teleportation protocol.

Quantum cloning and teleportation fidelity in the noncommutative phase-space

The formulation of the no-cloning theorem in the framework of phase-space noncommutative (NC) quantum mechanics (QM) is examined, and its implications for the computation of quantum cloning probabilities and teleportation fidelity are investigated through the Weyl–Wigner formulation of QM. The principles of QM re-edited in terms of a deformed Heisenberg–Weyl algebra are shown to provide a covariant formulation for the quantum fidelity, through which the results from the no-cloning theorem for the ordinary QM can be reproduced. Besides exhibiting an explicit correspondence between standard and NC QM for Gaussian Wigner functions, our results suggest a feasible interpretation for the NC continuous variable quantum cloning given in terms of quantum teleportation protocols.

Quantum Teleportation in High Dimensions.

Quantum teleportation allows a "disembodied" transmission of unknown quantum states between distant quantum systems. Yet, all teleportation experiments to date were limited to a two-dimensional subspace of quantized multiple levels of the quantum systems. Here, we propose a scheme for teleportation of arbitrarily high-dimensional photonic quantum states and demonstrate an example of teleporting a qutrit. Measurements over a complete set of 12 qutrit states in mutually unbiased bases yield a teleportation fidelity of 0.75(1), which is well above both the optimal single-copy qutrit state-estimation limit of 1/2 and maximal qubit-qutrit overlap of 2/3, thus confirming a genuine and nonclassical three-dimensional teleportation. Our work will enable advanced quantum technologies in high dimensions, since teleportation plays a central role in quantum repeaters and quantum networks.

Asymmetric quantum correlations in the dynamical Casimir effect

Considering the current available experimental studies on the dynamical Casimir effect (DCE) in superconducting microwave waveguides, we study asymmetric quantum correlations in microwave radiation. The asymmetric quantum correlations are created by the presence of detuning in the DCE. We study the asymmetric quantum steering and determine the parameter regions of one- and two-way quantum steering. It shows that steering from Bob to Alice is more difficult than steering from Alice to Bob. Moreover, we find regions that represent states that, although entangled, cannot be used for teleporting coherent states; however, the steerable states are appropriate for quantum teleportation. We investigate how the teleportation fidelity functions as an indicator of the quality of EPR steering in the DCE.

A class of nonlinear coherent states attached to Tsallis q-exponential

We construct a new class of nonlinear coherent states (NCS's) based on Tsallis q -exponential with $1 < q\leq 2$ . The special cases q = 2 and $ q\rightarrow 1$ recover the well-known harmonious states and canonical coherent states, respectively. Some non-classical properties are then studied. It has been found that this class of NCS's exhibits quadrature squeezing in the p component, amplitude squared squeezing in the Y component and negativity of Wigner function, however, it obeys a super-Poissonian statistics and exhibits a bunching behavior. In addition, we introduce nonlinear two-mode squeezed vacuum states (NTSVSs) attached to Tsallis q-exponential. These states are reduced to the well-known two-mode squeezed vacuum states (TSVSs) and pair coherent states (PCSs) when $ q\rightarrow 1$ and q = 2, respectively. Furthermore, the entanglement of the NTSVSs is examined by evaluating the linear entropy. Finally, we investigate the quantum teleportation of a coherent state using a NTSVS as a shared entangled resource instead of a TSVS. It is shown that the fidelity of teleportation depends on the nonlinearity function f(n) and recovers its standard expression in the linear limit $f(n)=1$ .

Improvement of the entanglement properties for entangled states using a superposition of number-conserving operations

The non-Gaussian operation, which can be easily implemented by current techniques, is an effective way for the improvement of the continuous-variable entanglement. Here, we theoretically propose a scheme for generating a number-conserving two-mode generalized superposition of products (TM-GSP) state by performing the -order GSP operations i.e. on an input two-mode squeezed vacuum (TMSV) state. Then, the entanglement properties of the TM-GSP state are analyzed detailedly by means of logarithmic negative, Einstein–Podolsky–Rosen (EPR) correlation and two-mode squeezing property. It is shown that, in contrast to the TMSV case, for the optimal choices of s1 and s2, the entanglement properties of the TM-GSP state can be improved by using symmetric GSP operations () and single-side GSP operations . Furthermore, the fidelity effect is also considered when the TM-GSP state is used as the entangled resource under the Braunstein and Kimble scheme. In terms of the optimal teleportation fidelity, it is found that the effect of the single GSP operation is equivalent to that of the case . This phenomenon also exists in logarithmic negative, EPR correlation and two-mode squeezing property. These results show that the prepared TM-GSP state may provide a well application in the fields of quantum information processing.

New approach to the fidelity of quantum teleportation based on the entangled state generated by beam splitter

Entangled states play an important role in quantum computation and quantum information processing. Beam splitter, a linear device, is often used to prepare entangled states and quantum mechanics representations. For any two input states, the formula for the fidelity is derived, including the Q function representation, the P function representation, and the Wigner function representation, by using the output states from beam splitter as a source of quantum teleportation. This provides a new way to calculate the fidelity. As applications, two single-mode squeezed vacuum states and coherent superposition state together with coherent state are used as inputs, and the fidelity for teleporting coherent state is discussed. Our method provide more alternatives for calculating fidelity of teleportaion.

Properties of two-mode squeezed Laguerre-polynomial-excited vacuum state generated by conditional measurement

We theoretically put forward a scheme to generate a new kind of the non-Gaussian state—two-mode squeezed Laguerre-polynomial-excited vacuum state (TMS-LPEVs) by using two beam splitters and conditional measurements with two kinds of TMS states inputs. It is interesting that the squeezed Bell state can be considered as a special case of TMS-LPEVs. Then we further examine its properties according to the entanglement entropy, the Einstein–Podolsky–Rosen correlation and the squeezing degree. It is found that for small auxiliary squeezing parameter r and high transmissivity, the entanglement entropy can be enhanced by single-photon measurement. When optimized over transmissivity, multiphoton measurements are beneficial to the improvement of the squeezing property and the teleportation fidelity in the region of larger λ accompanied by small auxiliary squeezing. More significantly, one can use a smaller squeezing parameter r to realize the improvements of the entanglement and the teleportation fidelity. These results may provide guidance for the implementation of experiments in quantum information and quantum computation.

Verified quantum information scrambling.

Quantum scrambling is the dispersal of local information into many-body quantum entanglements and correlations distributed throughout an entire system. This concept accompanies the dynamics of thermalization in closed quantum systems, and has recently emerged as a powerful tool for characterizing chaos in black holes1-4. However, the direct experimental measurement of quantum scrambling is difficult, owing to the exponential complexity of ergodic many-body entangled states. One way to characterize quantum scrambling is to measure an out-of-time-ordered correlation function (OTOC); however, because scrambling leads to their decay, OTOCs do not generally discriminate between quantum scrambling and ordinary decoherence. Here we implement a quantum circuit that provides a positive test for the scrambling features of a given unitary process5,6. This approach conditionally teleports a quantum state through the circuit, providing an unambiguous test for whether scrambling has occurred, while simultaneously measuring an OTOC. We engineer quantum scrambling processes through a tunable three-qubit unitary operation as part of a seven-qubit circuit on an ion trap quantum computer. Measured teleportation fidelities are typically about 80 per cent, and enable us to experimentally bound the scrambling-induced decay of the corresponding OTOC measurement.

Pauli-based fermionic teleportation with free massive particles by electron-exchange collisions

Fundamental non-locality in quantum mechanical scattering processes is investigated by means of Fermionic teleportation. Our scenario employs free massive particles, electrons and atoms, within a twofold electron-exchange collision approach whereby, in the first collision, also generating the necessary spin–spin entanglement between initially unpolarized electrons and atoms. It is shown that in a second collision an arbitrary spin polarization state of a free electron can be teleported onto the other electron which has never been in contact with the first one. The underlying scheme relies on and is a direct consequence of the Pauli-principle and makes use of a high symmetry in spin space thereby avoiding restoration of the teleported states. The scattering process (teleportation) is highly symmetric allowing for interchanging the electronic and atomic constituents without loss of generality. Re-interpretation of Li and Na data reveals the feasibility and capability of Fermionic teleportation demonstrated by numerical and experimental data for the teleportation fidelity.

Quantum teleportation of Dirac fields in noninertial frames with amplitude damping

We investigate quantum teleportation between users located in noninertial frames and analyze how the acceleration can improve the fidelity of quantum teleportation between two relatively accelerating partners. We see that the fidelity increases with respect to the acceleration as a consequence of the Unruh effect. In our scheme, Alice and Rob initially share a special $\mathsf{X}$-type state, Alice stays stationary, while Rob is uniformly accelerated with respect to Alice. We additionally study the system-environment dynamics in the noninertial frames, i.e., the $\mathsf{X}$-type state shared between Alice and Rob interacts with the environment via amplitude damping channel. Our results demonstrate a monogamy relation of the fidelity with acceleration and amplitude damping channel, these result suggest that the fidelity of quantum teleportation cannot be enhanced simultaneously by both the acceleration and amplitude damping channel. Such a property may have potential applications in protecting the fidelity of quantum teleportation performed by observers in relative motion.

Enhanced Quantum Teleportation between Noninertial Moved Parties by Weak Measurements

AbstractQuantum decoherence caused by the interaction between the quantum system and the environment is the most limiting factor for the applications of quantum teleportation. In this paper, investigated are the dynamic behavior of the coherence of the entangled source and the fidelity of the teleportation for two non‐inertial moved parties suffering the quantum noise induced by the background quantum fields, and a general protection scheme using weak measurements is provided. Explicitly, comparing the cases of using the initial state as well as the initial state , the coherence of the entangled state and teleportation fidelity with and without probabilistic weak measurements are studied. The results show that the decoherence caused by the thermalization of the two parties induced by their non‐inertial movements can be eliminated. The coherence and fidelity can be totally recovered with proper weak measurements and the optimal weak values are shown in relation with the spontaneous emission and excitation rates of the systems. However, the successful probability in the case of using the initial state is found to be much larger than that in the case of using the state and the preweak measurement is not needed with the initial state .

Correlated Effects in Pauli Channels for Quantum Teleportation

Correlated effects play a significant role in the study of quantum information processing. We investigate the two consecutive uses of the Pauli channels for quantum teleportation without resetting. We find that the existence of correlated action of noise channels is beneficial to improve the fidelity of noisy teleportation in Pauli channels, such as phase-damping, bit-flip and depolarizing channels. Namely, the fidelity increases with the increase of correlated parameter. Our study might provide a new perspective of enhancing the fidelity of quantum teleportation in noisy channels.

Controlled teleportation of qubit states: Relation between teleportation faithfulness, controller's authority, and tripartite entanglement

We consider the controlled quantum teleportation performed on a single copy of entangled three-qubit pure states and show how the fidelity of teleportation and the control power are related to the tripartite entanglement measures, namely, three-tangle and genuine concurrence. We characterize the states with extreme properties, and use them to derive tight lower and upper bounds on both the teleportation fidelity and control power for a given amount of entanglement. Furthermore, we discuss the usefulness of these two quantities for experimental detection and/or quantification of tripartite entanglement. In particular, we present the results which imply that the control power cannot be considered as a candidate for a degree of three-qubit entanglement complementary to the three-tangle as conjectured recently [K. Jeong, J. Kim, and S. Lee, Phys. Rev. A 93, 032328 (2016)]. Furthermore, we prove a mutual relation between teleportation fidelity and control power which provides attainable limits of the controller's authority for existing controlled teleportation schemes. Although those relations are derived for pure states, their extensions for mixed states are also examined.

Influence of Magnetic Field on Qutrit Teleportation under Intrinsic Decoherence

We study qutrit teleportation through a qutrit xyz chain, in the presence of intrinsic decoherence and a non-homogeneous magnetic field. We study the effects of intrinsic phase change, magnetic field and entanglement of the initial state of the channel. It is observed that while the intrinsic phase change and the non-homogeneity of the magnetic field have adverse effects on the teleportation fidelity, the entanglement of the initial state of the channeled enhances the latter. Moreover, the intrinsic decoherence may remove the ripples from the time curve that is delivered by the Schrodinger channel.