Showing papers on "Amplitude damping channel published in 2018"
TL;DR: In this article, a review of quantum-enhanced measurements can be found, including the use of more general quantum correlations such as quantum discord, identical particles, or non-trivial hamiltonians, and the estimation of thermodynamical parameters or parameters characterizing non-equilibrium states.
Abstract: Quantum-enhanced measurements exploit quantum mechanical effects for increasing the sensitivity of measurements of certain physical parameters and have great potential for both fundamental science and concrete applications. Most of the research has so far focused on using highly entangled states, which are, however, difficult to produce and to stabilize for a large number of constituents. In the following we review alternative mechanisms, notably the use of more general quantum correlations such as quantum discord, identical particles, or non-trivial hamiltonians; the estimation of thermodynamical parameters or parameters characterizing non-equilibrium states; and the use of quantum phase transitions. We describe both theoretically achievable enhancements and enhanced sensitivities, not primarily based on entanglement, that have already been demonstrated experimentally, and indicate some possible future research directions.
383 citations
TL;DR: It is formally demonstrated that the multiple-quantum coherence spectra, a specific family of OTOCs well known in NMR, can be used as an entanglement witness and as a direct probe of multiparticle entanglements.
Abstract: Out-of-time-order correlations (OTOCs) characterize the scrambling, or delocalization, of quantum information over all the degrees of freedom of a system and thus have been proposed as a proxy for chaos in quantum systems. Recent experimental progress in measuring OTOCs calls for a more thorough understanding of how these quantities characterize complex quantum systems, most importantly in terms of the buildup of entanglement. Although a connection between OTOCs and entanglement entropy has been derived, the latter only quantifies entanglement in pure systems and is hard to access experimentally. In this work, we formally demonstrate that the multiple-quantum coherence spectra, a specific family of OTOCs well known in NMR, can be used as an entanglement witness and as a direct probe of multiparticle entanglement. Our results open a path to experimentally testing the fascinating idea that entanglement is the underlying glue that links thermodynamics, statistical mechanics, and quantum gravity.
121 citations
TL;DR: In this article, a holographic dual of Fisher information metric for mixed states in the boundary field theory is proposed, which amounts to a measure for the distance between two mixed quantum states.
Abstract: In the context of relating AdS/CFT to quantum information theory, we propose a holographic dual of Fisher information metric for mixed states in the boundary field theory. This amounts to a holographic measure for the distance between two mixed quantum states. For a spherical subregion in the boundary we show that this is related to a particularly regularized volume enclosed by the Ryu-Takayanagi surface. We further argue that the quantum correction to the proposed Fisher information metric is related to the quantum correction to the boundary entanglement entropy. We discuss consequences of this connection.
73 citations
TL;DR: The zero-error setting is studied and provided and an improved upper bound on the classical capacity of the amplitude damping channel is derived and the strong converse property for the classical and private capacities of a new class of quantum channels is established.
Abstract: We investigate the classical communication over quantum channels when assisted by no-signaling and positive-partial-transpose-preserving (PPT) codes, for which both the optimal success probability of a given transmission rate and the one-shot $\epsilon $ -error capacity are formalized as semidefinite programs (SDPs). Based on this, we obtain improved SDP finite blocklength converse bounds of general quantum channels for entanglement-assisted codes and unassisted codes. Furthermore, we derive two SDP strong converse bounds for the classical capacity of general quantum channels: for any code with a rate exceeding either of the two bounds of the channel, the success probability vanishes exponentially fast as the number of channel uses increases. In particular, applying our efficiently computable bounds, we derive an improved upper bound on the classical capacity of the amplitude damping channel. We also establish the strong converse property for the classical and private capacities of a new class of quantum channels. We finally study the zero-error setting and provide efficiently computable upper bounds on the one-shot zero-error capacity of a general quantum channel.
54 citations
TL;DR: A solution to the nonstationary Schrodinger equation is found and in an analytical form a solution is found to the Schmidt mode for both stationary and dynamic problems.
Abstract: A system of two coupled quantum harmonic oscillators with the Hamiltonian H[over ]=1/2(1/m_{1}p[over ]_{1}^{2}+1/m_{2}p[over ]_{2}^{2}+Ax_{1}^{2}+Bx_{2}^{2}+Cx_{1}x_{2}) can be found in many applications of quantum and nonlinear physics, molecular chemistry, and biophysics. The stationary wave function of such a system is known, but its use for the analysis of quantum entanglement is complicated because of the complexity of computing the Schmidt modes. Moreover, there is no exact analytical solution to the nonstationary Schrodinger equation H[over ]Ψ=iℏ∂Ψ/∂t and Schmidt modes for such a dynamic system. In this paper we find a solution to the nonstationary Schrodinger equation; we also find in an analytical form a solution to the Schmidt mode for both stationary and dynamic problems. On the basis of the Schmidt modes, the quantum entanglement of the system under consideration is analyzed. It is shown that for certain parameters of the system, quantum entanglement can be very large.
53 citations
TL;DR: This Letter shows that communication bounded to the exchange of a single quantum particle can result in "two-way signaling," which is impossible in classical physics, and quantifies the discrepancy between classical and quantum scenarios by the probability of winning a game played by distant players.
Abstract: In this Letter we show that communication when restricted to a single information carrier (i.e., single particle) and finite speed of propagation is fundamentally limited for classical systems. On the other hand, quantum systems can surpass this limitation. We show that communication bounded to the exchange of a single quantum particle (in superposition of different spatial locations) can result in "two-way signaling," which is impossible in classical physics. We quantify the discrepancy between classical and quantum scenarios by the probability of winning a game played by distant players. We generalize our result to an arbitrary number of parties and we show that the probability of success is asymptotically decreasing to zero as the number of parties grows, for all classical strategies. In contrast, quantum strategy allows players to win the game with certainty.
45 citations
TL;DR: In this paper, an analytical formula for the max-relative entropy of entanglement of the qubit amplitude damping channel is presented, where the measure can be chosen on a channel-by-channel basis in order to make it as tight as possible.
Abstract: We provide a versatile upper bound on the number of maximally entangled qubits, or private bits, shared by two parties via a generic adaptive communication protocol over a quantum network when the use of classical communication is not restricted. Although our result follows the idea of Azuma et al. [Nat. Comm. 7, 13523 (2016)] of splitting the network into two parts, our approach relaxes their strong restriction, consisting of the use of a single entanglement measure in the quantification of the maximum amount of entanglement generated by the channels. In particular, in our bound the measure can be chosen on a channel-by-channel basis, in order to make it as tight as possible. This enables us to apply the relative entropy of entanglement, which often gives a state-of-the-art upper bound, on every Choi-simulable channel in the network, even when the other channels do not satisfy this property. We also develop tools to compute, or bound, the max-relative entropy of entanglement for channels that are invariant under phase rotations. In particular, we present an analytical formula for the max-relative entropy of entanglement of the qubit amplitude damping channel.
44 citations
TL;DR: It is shown that robust, seeding-dependent, genuine triple-photon entanglement in the fully seeded case is shown.
Abstract: We investigate the quantum entanglement of the three modes associated with the three-photon states obtained by triple-photon generation in a phase-matched third-order nonlinear optical interaction. Although the second-order processes have been extensively dealt with, there is no direct analogy between the second and third-order mechanisms. We show, for example, the absence of quantum entanglement between the quadratures of the three modes in the case of spontaneous parametric triple-photon generation. However, we show robust, seeding-dependent, genuine triple-photon entanglement in the fully seeded case.
41 citations
TL;DR: This work discusses quantum error-correcting codes adapted to amplitude damping channels for higher dimensional systems (qudits) and constructs families of single-error-Correcting quantum codes that can be used for both cases.
Abstract: Traditional quantum error-correcting codes are designed for the depolarizing channel modeled by generalized Pauli errors occurring with equal probability. Amplitude damping channels model, in general, the decay process of a multilevel atom or energy dissipation of a bosonic system with Markovian bath at zero temperature. We discuss quantum error-correcting codes adapted to amplitude damping channels for higher dimensional systems (qudits). For multi-level atoms, we consider a natural kind of decay process, and for bosonic systems, we consider the qudit amplitude damping channel obtained by truncating the Fock basis of the bosonic modes (e.g., the number of photons) to a certain maximum occupation number. We construct families of single-error-correcting quantum codes that can be used for both cases. Our codes have larger code dimensions than the previously known single-error-correcting codes of the same lengths. In addition, we present families of multi-error correcting codes for these two channels, as well as generalizations of our construction technique to error-correcting codes for the qutrit $V$ and $\Lambda $ channels.
39 citations
TL;DR: In this article, the authors investigated the interplay between the degrees of entanglement and randomness in pure states and unitary channels, and showed that R\'enyi entropies averaged over designs of the same order are almost maximal.
Abstract: The entanglement properties of random quantum states or dynamics are important to the study of a broad spectrum of disciplines of physics, ranging from quantum information to high energy and many-body physics. This Letter investigates the interplay between the degrees of entanglement and randomness in pure states and unitary channels. We reveal strong connections between designs (distributions of states or unitaries that match certain moments of the uniform Haar measure) and generalized entropies (entropic functions that depend on certain powers of the density operator), by showing that R\'enyi entanglement entropies averaged over designs of the same order are almost maximal. This strengthens the celebrated Page's theorem. Moreover, we find that designs of an order that is logarithmic in the dimension maximize all R\'enyi entanglement entropies and so are completely random in terms of the entanglement spectrum. Our results relate the behaviors of R\'enyi entanglement entropies to the complexity of scrambling and quantum chaos in terms of the degree of randomness, and suggest a generalization of the fast scrambling conjecture.
38 citations
TL;DR: In this article, the authors design and experimentally demonstrate a scheme that verifies entanglement in the presence of at least 14.8 ± 0.1 dB of added loss, equivalent to approximately 80 km of telecommunication fiber.
Abstract: Entanglement is the key resource for many long-range quantum information tasks, including secure communication and fundamental tests of quantum physics. These tasks require robust verification of shared entanglement, but performing it over long distances is presently technologically intractable because the loss through an optical fiber or free-space channel opens up a detection loophole. We design and experimentally demonstrate a scheme that verifies entanglement in the presence of at least 14.8 ± 0.1 dB of added loss, equivalent to approximately 80 km of telecommunication fiber. Our protocol relies on entanglement swapping to herald the presence of a photon after the lossy channel, enabling event-ready implementation of quantum steering. This result overcomes the key barrier in device-independent communication under realistic high-loss scenarios and in the realization of a quantum repeater.
TL;DR: In this article, the authors study the limitations for the interconversion between coherence and entanglement and prove a fundamental no-go theorem, stating that a general resource theory of superposition does not allow for entenglement activation.
Abstract: Quantum entanglement and coherence are two fundamental features of nature, arising from the superposition principle of quantum mechanics. While considered as puzzling phenomena in the early days of quantum theory, it is only very recently that entanglement and coherence have been recognized as resources for the emerging quantum technologies, including quantum metrology, quantum communication, and quantum computing. In this work we study the limitations for the interconversion between coherence and entanglement. We prove a fundamental no-go theorem, stating that a general resource theory of superposition does not allow for entanglement activation. By constructing a quantum controlled-not gate as a free operation, we experimentally show that such activation is possible within the more constrained framework of quantum coherence. By using recent results from coherence theory, we further show that the trace norm entanglement is not a strong entanglement monotone.
TL;DR: In this article, the authors consider the problem of quantum search of a marked node on a complete graph of nodes in the presence of both static disorder and nonzero coupling to an environment and show that, given fixed and finite levels of disorder and thermal fluctuations, there is an optimal range of bath temperatures that can significantly improve the success probability.
Abstract: Two main obstacles for observing quantum advantage in noisy intermediate-scale quantum computers (NISQ) are the finite-precision effects due to control errors, or disorders, and decoherence effects due to thermal fluctuations. It has been shown that dissipative quantum computation is possible in the presence of an idealized fully engineered bath. However, it is not clear, in general, what performance can be achieved by NISQ when internal bath degrees of freedom are not controllable. In this work, we consider the task of quantum search of a marked node on a complete graph of $n$ nodes in the presence of both static disorder and nonzero coupling to an environment. We show that, given fixed and finite levels of disorder and thermal fluctuations, there is an optimal range of bath temperatures that can significantly improve the success probability of the algorithm. Remarkably for a fixed disorder strength $\ensuremath{\sigma}$, the system relaxation time decreases for higher temperatures within a robust range of parameters. In particular, we demonstrate that for strong disorder, the presence of a thermal bath increases the success probability from $1/(n{\ensuremath{\sigma}}^{2})$ to at least $1/2$. While the asymptotic running time is approximately maintained, the need to repeat the algorithm many times and issues associated with unitary over-rotations can be avoided as the system relaxes to an absorbing steady state. Furthermore, we discuss for what regimes of disorder and bath parameters quantum speedup is possible and mention conditions for which similar phenomena can be observed in more general families of graphs. Our work highlights that in the presence of static disorder, even nonengineered environmental interactions can be beneficial for a quantum algorithm.
TL;DR: In this article, an all-optical experiment to quantify non-Markovianity in an open quantum system through quantum coherence of a single quantum bit is presented, where an amplitude damping channel implemented by an optical setup with an intense laser beam simulating a single-photon polarization is analytically evaluated.
Abstract: We propose an all-optical experiment to quantify non-Markovianity in an open quantum system through quantum coherence of a single quantum bit. We use an amplitude damping channel implemented by an optical setup with an intense laser beam simulating a single-photon polarization. The optimization over initial states required to quantify non-Markovianity is analytically evaluated. The experimental results are in a very good agreement with the theoretical predictions.
TL;DR: In this paper, a three-qubit NMR quantum information processor was used for the protection of tripartite entangled states, namely, the maximally entangled Greenberger-Horne-Zeilinger (GHZ) and W states, using dynamical decoupling.
Abstract: We embarked upon the task of experimental protection of different classes of tripartite entangled states, namely, the maximally entangled Greenberger-Horne-Zeilinger (GHZ) and W states and the tripartite entangled state called the $W\overline{W}$ state, using dynamical decoupling. The states were created on a three-qubit NMR quantum information processor and allowed to evolve in the naturally noisy NMR environment. Tripartite entanglement was monitored at each time instant during state evolution, using negativity as an entanglement measure. It was found that the W state is most robust while the GHZ-type states are most fragile against the natural decoherence present in the NMR system. The $W\overline{W}$ state, which is in the GHZ class yet stores entanglement in a manner akin to the W state, surprisingly turned out to be more robust than the GHZ state. The experimental data were best modeled by considering the main noise channel to be an uncorrelated phase damping channel acting independently on each qubit, along with a generalized amplitude damping channel. Using dynamical decoupling, we were able to achieve a significant protection of entanglement for GHZ states. There was a marginal improvement in the state fidelity for the W state (which is already robust against natural system decoherence), while the $W\overline{W}$ state showed a significant improvement in fidelity and protection against decoherence.
TL;DR: A protocol is presented that estimates a lower bound on a channel’s quantum capacity, even when there are arbitrarily correlated errors, and applies this method to a superconducting qubit in experiment.
Abstract: The central figure of merit for quantum memories and quantum communication devices is their capacity to store and transmit quantum information. Here, we present a protocol that estimates a lower bound on a channel's quantum capacity, even when there are arbitrarily correlated errors. One application of these protocols is to test the performance of quantum repeaters for transmitting quantum information. Our protocol is easy to implement and comes in two versions. The first estimates the one-shot quantum capacity by preparing and measuring in two different bases, where all involved qubits are used as test qubits. The second verifies on-the-fly that a channel's one-shot quantum capacity exceeds a minimal tolerated value while storing or communicating data. We discuss the performance using simple examples, such as the dephasing channel for which our method is asymptotically optimal. Finally, we apply our method to a superconducting qubit in experiment.
TL;DR: In this paper, the effects of the environment on the entropic uncertainty lower bound in the presence of weak measurement and measurement reversal are studied. But the model is restricted to the case where there is an additional particle as a quantum memory.
Abstract: The uncertainty principle is an inherent characteristic of quantum mechanics. This principle can be formulated in various form. Fundamentally, this principle can be expressed in terms of the standard deviation of the measured observables. In quantum information theory the preferred mathematical quantity to express the entropic uncertainty relation is the Shannon's entropy. In this work, we consider the generalized entropic uncertainty relation in which there is an additional particle as a quantum memory. Alice measures on her particle $A$ and Bob, with memory particle $B$, predicts the Alice's measurement outcomes. We study the effects of the environment on the entropic uncertainty lower bound in the presence of weak measurement and measurement reversal. The dynamical model that is intended in this work is as follows: First the weak measurement is performed, Second the decoherence affects on the system and at last the measurement reversal is performed on quantum system . Here we consider the generalized amplitude damping channel and depolarizing channel as environmental noises. We will show that in the presence of weak measurement and measurement reversal, despite the presence of environmental factors, the entropic uncertainty lower bound dropped to an optimal minimum value. In fact, weak measurement and measurement reversal enhance the quantum correlation between the subsystems $A$ and $B$ thus the uncertainty of Bob about Alice's measurement outcomes reduces.
TL;DR: In this paper, the authors analyzed the evolution of coherence in a two-qubit system going through the amplitude damping channel and derived an equation for the output states after one or two subsystems have been used to analyze the coherence of their outputs.
Abstract: In this paper, we analyze the evolution of quantum coherence in a two-qubit system going through the amplitude damping channel. After they have gone through this channel many times, we analyze the systems with respect to the coherence of their output states. When only one subsystem goes through the channel, frozen coherence occurs if and only if this subsystem is incoherent and an auxiliary condition is satisfied for the other subsystem. When two subsystems go through this quantum channel, quantum coherence can be frozen if and only if the two subsystems are both incoherent. We also investigate the evolution of coherence for maximally incoherent-coherent states and derive an equation for the output states after one or two subsystems have gone through the amplitude damping channel.
TL;DR: With these tools, it is shown that many-body quantum chaos is neither highly entangled nor delocalized in the Hilbert space, contrary to conventionally expected signatures of quantum chaos.
Abstract: We uncover signatures of quantum chaos in the many-body dynamics of a Bose-Einstein condensate-based quantum ratchet in a toroidal trap. We propose measures including entanglement, condensate depletion, and spreading over a fixed basis in many-body Hilbert space, which quantitatively identify the region in which quantum chaotic many-body dynamics occurs, where random matrix theory is limited or inaccessible. With these tools, we show that many-body quantum chaos is neither highly entangled nor delocalized in the Hilbert space, contrary to conventionally expected signatures of quantum chaos.
TL;DR: Wei et al. as discussed by the authors proposed an improved protocol with single-qubit measurements and the same fourqubit quantum channel, lessening the difficulty and intensity of necessary operations.
Abstract: Recently, Zhao-Hui Wei et al. (Int. J. Theor. Phys. 55, 4687, 2016) proposed an improved quantum teleportation scheme for one three-qubit unknown state with a four-qubit quantum channel based on the original one proposed by Binayak S. Choudhury and Arpan Dhara (Int. J. Theor. Phys. 55, 3393, 2016). According to their schemes, the three-qubit entangled state could be teleported with one four-qubit cluster state and five-qubit joint measurements or four-qubit joint measurements. In this paper, we present an improved protocol only with single-qubit measurements and the same four-qubit quantum channel, lessening the difficulty and intensity of necessary operations.
TL;DR: In this article, the authors demonstrate quantum enhanced communication over an amplitude damping noisy channel with only two uses of the channel per bit and a single entangling gate at the decoder.
Abstract: Encoding schemes and error-correcting codes are widely used in information technology to improve the reliability of data transmission over real-world communication channels. Quantum information protocols can further enhance the performance in data transmission by encoding a message in quantum states; however, most proposals to date have focused on the regime of a large number of uses of the noisy channel, which is unfeasible with current quantum technology. We experimentally demonstrate quantum enhanced communication over an amplitude damping noisy channel with only two uses of the channel per bit and a single entangling gate at the decoder. By simulating the channel using a photonic interferometric setup, we experimentally increase the reliability of transmitting a data bit by greater than 20% for a certain damping range over classically sending the message twice. We show how our methodology can be extended to larger systems by simulating the transmission of a single bit with up to eight uses of the channel and a two-bit message with three uses of the channel, predicting a quantum enhancement in all cases.
TL;DR: An upper bound on the probability for a successful measurement operation to produce a maximally entangled state without any further local operations is got and a protocol is constructed with the optimal entanglement concentration rate and less consumption of local operations and classical communication.
Abstract: Quantum entanglement is an indispensable resource for many significant quantum information processing tasks. However, in practice, it is difficult to distribute quantum entanglement over a long distance, due to the absorption and noise in quantum channels. A solution to this challenge is a quantum repeater, which can extend the distance of entanglement distribution. In this scheme, the time consumption of classical communication and local operations takes an important place with respect to time efficiency. Motivated by this observation, we consider a basic quantum repeater scheme that focuses on not only the optimal rate of entanglement concentration but also the complexity of local operations and classical communication. First, we consider the case where two different two-qubit pure states are initially distributed in the scenario. We construct a protocol with the optimal entanglement-concentration rate and less consumption of local operations and classical communication. We also find a criterion for the projective measurements to achieve the optimal probability of creating a maximally entangled state between the two ends. Second, we consider the case in which two general pure states are prepared and general measurements are allowed. We get an upper bound on the probability for a successful measurement operation to produce a maximally entangled state without any further local operations.
TL;DR: In this article, it was shown that for a large range of parameters, the quantum non-bilocal correlations are preserved against decoherence by taking into account the average success rate of the postselection governing weak measurements.
Abstract: A tripartite quantum network is said to be bilocal if two independent sources produce a pair of bipartite entangled states. Quantum nonbilocal correlation emerges when the central party which possesses two particles from two different sources performs Bell-state measurement on them and nonlocality is generated between the other two uncorrelated systems in this entanglement-swapping protocol. The interaction of such systems with the environment reduces quantum nonbilocal correlations. Here we show that the diminishing effect modeled by the amplitude damping channel can be slowed down by employing the technique of weak measurements and reversals. It is demonstrated that for a large range of parameters, the quantum nonbilocal correlations are preserved against decoherence by taking into account the average success rate of the postselection governing weak measurements.
TL;DR: In this article, the authors investigated electron spin operations driven by applied electric fields in a semiconductor double quantum dot (DQD) formed in a nanowire with longitudinal potential modulated by local gating.
Abstract: We theoretically investigate electron spin operations driven by applied electric fields in a semiconductor double quantum dot (DQD) formed in a nanowire with longitudinal potential modulated by local gating. We develop a model that describes the process of loading and unloading the DQD taking into account the overlap between the electron wave function and the leads. Such a model considers the spatial occupation and the spin Pauli blockade in a time-dependent fashion due to the highly mixed states driven by the external electric field. Moreover, we present a road map based on the quantum optimal control theory (QOCT) to find a specific electric field that performs two-qubit quantum gates on a faster timescale and with higher possible fidelity. By employing the QOCT, we demonstrate the possibility of performing within high efficiency a universal set of quantum gates ${$cnot, H, and $\mathrm{T}}$, where cnot is the controlled-not gate, H is the Hadamard gate, and T is the $\ensuremath{\pi}/8$ gate, even in the presence of the loading/unloading process and charge noise effects. Furthermore, by varying the intensity of the applied magnetic field $B$, the optimized fidelity of the gates oscillates with a period inversely proportional to the gate operation time ${t}_{f}$. This behavior can be useful to attain higher fidelity for fast gate operations ($g1$ GHz) by appropriately choosing $B$ and ${t}_{f}$ to produce a maximum of the oscillation.
TL;DR: In this article, the authors discussed the dynamics of quantum uncertainty relations of quantum coherence and their lower bounds under the amplitude damping channel (ADC) for two pairs of measurement bases with the same maximum overlap.
Abstract: In this paper, we discuss quantum uncertainty relations of quantum coherence through a different method from Ref. [52]. Some lower bounds with parameters and their minimal bounds are obtained. Moreover, we find that for two pairs of measurement bases with the same maximum overlap, quantum uncertainty relations and lower bounds with parameters are different, but the minimal bounds are the same. In addition, we discuss the dynamics of quantum uncertainty relations of quantum coherence and their lower bounds under the amplitude damping channel (ADC). We find that the ADC will change the uncertainty relations and their lower bounds, and their tendencies depend on the initial state.
TL;DR: In this paper, a mixed-three-spin (1/2, 1, 1/2) cell of a mixed N-spin chain with Ising-XY model is introduced, for which pair spins (1, 1 2 ) have Ising type and Dzyaloshinskii-Moriya (DM) interactions together.
Abstract: In the present work, initially a mixed-three-spin (1/2,1,1/2) cell of a mixed-N-spin chain with Ising-XY model is introduced, for which pair spins (1,1/2) have Ising-type interaction and pair spins (1/2,1/2) have both XY-type and Dzyaloshinskii-Moriya(DM) interactions together. An external homogeneous magnetic field B is considered for the system in thermal equilibrium. Integer-spins have a single-ion anisotropy property with coefficient {\zeta}. Then, we investigate the quantum entanglement between half-spins (1/2,1/2), by means of the concurrence. Classical correlation(CC) for this pair of spins is investigated as well as the concurrence and some interesting the temperature, the magnetic field and the DM interaction properties are expressed. Moreover, single-ion anisotropy effects on the correlation between half-spins is verified. According to the verifications based on the communication channels category by D. Rossini, V. Giovannetti and R. Fazio 63, we theoretically consider such tripartite spin model as an ideal quantum channel, then calculate its information transmission rate and express some differences in behaviour between this suggested model and introduced simple models in the previous works(chains without spin integer and DM interaction) from information transferring protocol point of view.
TL;DR: In this paper, the dynamics of coherence-induced state ordering under incoherent channels, particularly four specific Markovian channels: amplitude damping, phase damping channel, depolarizing channel and bit flit channel for single-qubit states.
Abstract: We study the dynamics of coherence-induced state ordering under incoherent channels, particularly four specific Markovian channels: amplitude damping channel, phase damping channel, depolarizing channel and bit flit channel for single-qubit states. We show that the amplitude damping channel, phase damping channel, and depolarizing channel do not change the coherence-induced state ordering by l1 norm of coherence, relative entropy of coherence, geometric measure of coherence, and Tsallis relative α-entropies, while the bit flit channel does change for some special cases.
TL;DR: In this paper, the quantum correlations quantified via quantum discord, quantum deficit, and the generalized negativity are simulated for reference and it is shown that quantum coherence, discord, and deficit are nonzero whereas the negativity is zero in some ranges of model parameters and temperature.
Abstract: The l 1 norm and the relative entropy have been recently proposed as a information measure of quantum coherence (Baumgratz et al., 2014). Here their properties are studied for the thermal quantum state in a spin-1 Heisenberg model with various couplings, external magnetic fields, and temperatures as well. Quantum correlations quantified via quantum discord, quantum deficit, and the generalized negativity are simulated for reference. It is shown that quantum coherence, discord, and deficit are nonzero whereas the negativity is zero in some ranges of model parameters and temperature. Moreover, quantum coherence, discord, and deficit are more robust than the negativity against temperature and magnetic field. However, all those quantities at lower temperatures behave similarly. Remarkably, quantum deficit exhibits double sudden changes under suitable conditions while quantum coherence, discord, and entanglement do not display such a phenomenon. The hierarchy of two coherence measures and the hierarchy of quantum discord and deficit are discussed. Those are useful for understanding quantumness in high-dimensional mixed states and quantum tasks.
TL;DR: In this paper, the authors examined the dynamics of quantum and classical correlations of the system initially exists in Werner states and showed that the sudden death and sudden birth of quantum entanglement occur but the geometric measure of quantum discord remains non-zero.
Abstract: We discuss some new features of the model of two two-level atoms interacting with two single-mode thermal cavity field via multi-photon transitions under intensity-dependent coupling. We examine the dynamics of quantum and classical correlations of the system initially exists in Werner states. The results show that the sudden death and sudden birth of quantum entanglement occur but the geometric measure of quantum discord remains non-zero. It is observed that, by increasing the number of photons, the periods become shorter and the quantum discord and entanglement become irregular.
TL;DR: In this paper, the authors theoretically investigated the time evolution of quantum entanglement of an EPR pair in a random-field XXZ spin chain model in the Anderson localized (AL) and many-body localized (MBL) phase.
Abstract: The Einstein-Podolsky-Rosen (EPR) pair of qubits plays a critical role in many quantum protocol applications such as quantum communication and quantum teleportation. Due to interaction with the environment, an EPR pair might lose its entanglement and can no longer serve as useful quantum resources. On the other hand, it has been suggested that introducing disorder into environment might help to prevent thermalization and improve the preservation of entanglement. Here, we theoretically investigate the time evolution of quantum entanglement of an EPR pair in a random-field XXZ spin chain model in the Anderson localized (AL) and many-body localized (MBL) phase. We find that the entanglement between the qubits decreases and approaches to a plateau in the AL phase, but shows a power-law decrease after some critical time determined by the interaction strength in the MBL phase. Our findings, on one hand, shed lights on applying AL/MBL to improve quantum information storage; on the other hand, can be used as a practical indicator to distinguish the AL and MBL phase.