Entanglement Loss Research Articles

Identifying Sources of Entanglement Loss in Photodriven Molecular Electron Spin Teleportation.

We report on an electron donor-electron acceptor-stable radical (D-A-R•) molecule in which an electron spin state first prepared on R• is followed by photogeneration of an entangled singlet 1[D•+-A•-] spin pair to produce D•+-A•--R•. Since the A•- and R• spins within D•+-A•--R• are uncorrelated, spin teleportation from R• to D•+ occurs with a maximal 25% efficiency only for the singlet pair 1(A•--R•) by spin-allowed electron transfer from A•- to R•. However, since 1[D•+-A•-] is sufficiently long-lived, coherent spin mixing involving the unreactive 3(A•--R•) population affects entanglement and teleportation within D•+-A•--R•. Pulse electron paramagnetic resonance experiments show a direct correlation between electron spin flip-flops and entanglement loss, providing information for designing molecular materials to serve as nanoscale quantum device interconnects.

Fluctuation in the fidelity of information recovery from Hawking radiation

The interior of a pure-state black hole is known to be reconstructed from the Petz map by collecting a sufficiently large amount of the emitted Hawking radiation. This was established based on the Euclidean replica wormhole, which comes from an ensemble averaging over gravitational theories. On the other hand, this means that the Page curve and the interior reconstruction are both ensemble averages; thus, there is a possibility of large errors. In the previous study [R. Bousso and M. Miyaji, Fluctuations in the entropy of Hawking radiation], it was shown that the entropy of the Hawking radiation has fluctuation of order e−SBH, thus is typical in the ensemble. In the present article, we show that the fluctuations in the information recovery are similarly suppressed by the factor e−SBH by studying the fluctuations of the relative entropy difference in the encoding map and the entanglement fidelity of the Petz map. This result establishes the typicality of the information recovery in the ensemble. In addition, we also compute the entanglement loss of the encoding map. Published by the American Physical Society 2024

Port-based entanglement teleportation via noisy resource states

Port-based teleportation (PBT) represents a variation of the standard quantum teleportation and is currently being employed and explored within the field of quantum information processing owing to its various applications. In this study, we focus on PBT protocol when the resource state is disrupted by local Pauli noises. Here, we fully characterise the channel of the noisy PBT protocol using Krauss representation. Especially, by exploiting the application of PBT for entanglement distribution necessary in realizing quantum networks, we investigate entanglement transmission through this protocol for each qubit considering noisy resource states, denoted as port-based entanglement teleportation (PBET). Finally, we derive upper and lower bounds for the teleported entanglement as a function of the initial entanglement and the noises. Our study demonstrates that quantum entanglement can be efficiently distributed by protocols utilizing large-sized resource states in the presence of noise and is expected to serve as a reliable guide for developing optimized PBET protocols. To obtain these results, we address that the order of entanglement of two qubit states is preserved through the local Pauli channel, and identify the boundaries of entanglement loss through this teleportation channel.

Quantum Entanglement Protection by Utilizing Classical Noises

AbstractNoise is often considered as the biggest enemy of maintaining quantum entanglement. However, in this paper, it shows quantum entanglement can be protected by introducing extra noises to a quantum system. As an example, the dynamics of a two‐qubit system coupled to a cavity is studied under the influence of three noises, a quantized noise from the leakage of the cavity and two classical noises in the couplings between the two‐qubit system and the cavity. The master equation beyond the Markov approximation is derived and the mechanism of the entanglement protection is analyzed in a special case with analytical solutions. In short, the entanglement loss caused by the dissipation to the bath might be weaken by introducing high‐frequency classical noises properly. The numerical simulations not only confirm the feasibility of protecting entanglement by noises but also reveal that the properties of the classical noises have a significant impact on the performance of the entanglement protection.

Environment assisted quantum model for studying RNA-DNA-error correlation created due to the base tautomery

The adaptive mutation phenomenon has been drawing the attention of biologists for several decades in evolutionist community. In this study, we propose a quantum mechanical model of adaptive mutation based on the implications of the theory of open quantum systems. We survey a new framework that explain how random point mutations can be stabilized and directed to be adapted with the stresses introduced by the environments according to the microscopic rules dictated by constraints of quantum mechanics. We consider a pair of entangled qubits consist of DNA and mRNA pair, each coupled to a distinct reservoir for analyzing the spreed of entanglement using time-dependent perturbation theory. The reservoirs are physical demonstrations of the cytoplasm and nucleoplasm and surrounding environments of mRNA and DNA, respectively. Our predictions confirm the role of the environmental-assisted quantum progression of adaptive mutations. Computing the concurrence as a measure that determines to what extent the bipartite DNA-mRNA can be correlated through entanglement, is given. Preventing the entanglement loss is crucial for controlling unfavorable point mutations under environmental influences. We explore which physical parameters may affect the preservation of entanglement between DNA and mRNA pair systems, despite the destructive role of interaction with the environments.

Black holes entangled by radiation

We construct three models to describe the scenario where two eternal black holes are separated by a flat space, and can eventually be entangled by exchanging radiation. In the doubly holographic setup, we compute the entanglement entropy and mutual information among subsystems and obtain the dynamic phase structure of the entanglement. The formation of entanglement between these two black holes is delayed by the space which the radiation must travel through. If the black holes exchange sufficient Hawking modes, the final state is characterized by a connected entanglement wedge; otherwise, the final entanglement wedge contains two separate islands. In the former case, the entanglement wedge of the black holes forms at the time scale proportional to the size of the flat space between them. While in both cases, the unitarity of the evolution is preserved. When the sizes of the black holes are not equal, we observe a loss of entanglement between the smaller black hole and the radiation at late times. On the field theory side, we consider two Sachdev-Ye-Kitaev (SYK) clusters coupled to a Majorana chain, which resemble two black holes connected by a radiation region. We numerically compute the same entanglement measures and obtain similar phase structures as the bulk results. In general, a time delay of the entanglement between the SYK clusters is found in cases with a long Majorana chain. In particular, when the SYK clusters are different in size, similar entanglement loss between the smaller SYK cluster and the Majorana chain is observed. Finally, we investigate a chain model composed of EPR clusters with particles exchanging between neighboring clusters and reproduce the features of entanglement observed in the previous models.

Diffraction-induced entanglement loss of high-dimensional orbital angular-momentum states

The entanglement loss of high-dimensional entangled orbital angular-momentum states in far-field diffraction by a circular aperture was studied theoretically. A general expression for high-dimensional entanglement decay is provided. The results show that the loss depends on both the parity and the magnitude of the orbital angular-momentum index, and it is not affected by a small misalignment error of the aperture.

Entanglement dynamics between Ising spins and a central ancilla

We investigate competing entanglement dynamics in an Ising spin chain coupled to an external central ancilla qudit. In studying the real-time behavior following a quench from an unentangled spin-ancilla state, we find that the ancilla entanglement entropy ${S}_{vN;\mathcal{A}}$ tracks the dynamical phase transition in the underlying spin system. In this composite setting, purely spin-spin entanglement metrics such as mutual information and quantum Fisher information (QFI) decay as the ancilla entanglement entropy grows. We define multipartite entanglement loss (MEL) as the difference between collective magnetic fluctuations and QFI, which is zero in the pure spin chain limit. MEL directly quantifies the ancilla's effect on the development of spin-spin entanglement. One of our central results is that we find ${M}_{el}(t)\ensuremath{\propto}{e}^{{S}_{vN;\mathcal{A}}(t)}$. Our results provide a platform for exploring composite system entanglement dynamics and suggest that MEL serves as a quantitative estimate of information entropy shared between collective spins and the ancilla qudit. Our results present a framework that connects physical spin fluctuations, QFI, and bipartite entanglement entropy between collective quantum systems.

Ingestion and characterization of plastic debris by loggerhead sea turtle, Caretta caretta, in the Balearic Islands

Plastic waste has become ubiquitous pollutants in seas and oceans and can affect a wide range of species. For some marine species, plastic debris could pose a considerable threat through entanglement, ingestion, and habitat degradation and loss. Sea turtles are one of the most sensitive species, as their migratory behaviour and multifaceted life cycles make these reptiles especially vulnerable to the negative effects of plastic debris. The present study aimed to assess the amount and composition of plastic debris ingested by loggerhead turtles (Caretta caretta, Linnaeus, 1758) in the Balearic Islands Sea, thusly providing new information to complete the knowledge for this topic. In this work, 45 stranded dead C. caretta specimens were necropsied, and their digestive tract content analysed for the presence of plastic debris. Plastic objects were observed in 27 individuals (60.0%), with an average of 12.7 ± 4.7 plastic items per turtle. Litter in the faecal pellet was also monitored in 67 living individuals, observing plastic elements in 46 (68.7%) of the specimens, reporting an average of 9.7 ± 3.3 plastic elements per individual. Overall, 785 plastic items were found, measured, weighed and categorized according to size, colour, shape, and type of polymer. The main elements ingested were plastic sheets that were found in 65.3% of the turtles analysed, being white (42.7%) and transparent (29.2%) the most predominant colours. Most elements were macroplastics (59.3%), while microplastics were not found. Fourier Transform Infrared Spectrometry (FT-IR) analysis showed that high-density polyethylene and polypropylene were the main polymer plastics, representing 42.3% and 33.8% of the total, respectively. In conclusion, the high occurrence of plastic debris determined in the present study evidenced for the first time plastic ingestion in loggerhead turtles in the Balearic Islands, and highlights C. caretta as a bioindicator organism for marine pollution.

Diffraction-Induced Entanglement Loss of High-Dimensional Orbital Angular-Momentum States

Diffraction-Induced Entanglement Loss of High-Dimensional Orbital Angular-Momentum States

Quantum coherence induced by a flux qubit coupled by a resonator coherent field through a two-photon interaction

The intrinsic decoherence effects on a flux qubit coupled to a resonator through a two-photon interaction where the resonator field is initially in coherent and even coherent states are investigated. The qubit-resonator entanglement and coherence loss (mixedness) of the system and its subsystems are examined using entropy and negativity. The ability of the qubit-resonator interaction to generate quantum coherence (qubit-resonator entanglement and mixedness) is shown to be dependent on the initial cavity non-classicality, detuning, and decoherence. For larger values of the qubit-resonator detuning, the initial resonator non-classicality can enhance the generation and stability of quantum coherence. The decoherence degrades the qubit-resonator entanglement and destroys the sudden death-birth entanglement.

Entanglement of truncated quantum states

We investigate the impact of Hilbert-space truncation upon the entanglement of an initially maximally entangled m × m bipartite quantum state, after propagation under an entanglement-preserving n × n (n ⩾ m) unitary. Truncation—physically enforced, e.g., by a detector’s finite cross section—projects the state onto an s × s-dimensional subspace (3 ⩽ s ⩽ n). For a random local unitary evolution, we obtain a simple analytical formula that expresses the truncation-induced entanglement loss as a function of n, m and s.

Effect of gamma irradiation on the oxygen barrier properties in ethyl‐vinyl acetate/ethylene‐vinyl alcohol/ethyl‐vinyl acetate multilayer film

AbstractThe potential changes of single‐use plastic materials (EVA/EVOH/EVA multilayer film in this study) used in biopharmaceutical and food‐packaging industries are investigated after several gamma irradiation doses: 30, 50, 115, and 270 kGy, and for nonsterilized samples (0 kGy) from a point of view of mechanical properties, thermal properties and permeability properties. Tensile tests, differential scanning calorimetry (DSC), oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) are performed on the multilayer film. For irradiation doses below 50 kGy, thermal and water vapor barrier properties are not altered. For higher doses (50 to 270 kGy), mechanical, thermal and water vapor barrier properties are slightly altered whereas oxygen barrier property decreases from 13 to 27 cm3.m−2.day−1. This slight change is shown not to happen due to chain entanglement or chain mobility loss in the amorphous phase of the different polymers. It rather comes from a change of the chemical environment of the EVOH layer.

Entanglement Dynamics of a Dissipative Two-qubit System Under the Influence of a Global Environment

In this paper we propose a two-qubit system exposed to a common thermal reservoir as the source of dissipation. Starting from the master equation, specially its dissipator part, we find its explicit solution through which we investigate the time evolution of entanglement between the two qubits via concurrence measure by considering different initial entangled states. Our results show that the system can be found in Markovian and non-Markovian regimes depending on the involved parameters. In the Markovian regime, the amount of entanglement permanently deceases and therefore the two-qubit system is finally found in a separable state. In the other hand, in non-Markovian regime, the two-qubit system exchanges its entanglement with environment in such a way that it can recover its entanglement loss as time passes. In this case, the system undergoes a death of entanglement at some intervals of time, however, then restores its entanglement and gradually reaches to a maximally stable entangled state. Restoring of entanglement is a remarkable outcome of global environment in comparison with its local counterpart. Also, the amount of entanglement can be adjusted by choosing appropriate parameters involved in the proposed model such as thermal excitation number as well as the initial condition of the two-qubit state of system.

Universal entanglement loss induced by angular uncertainty

We study the diffraction of two maximally entangled qubits encoded into spatial modes of light with orbital angular momenta ±ℏl0, on angular apertures. Exploiting the uncertainty relation between angular position and momentum, we quantify the diffraction-induced entanglement loss, for different l0, as a function of the angular uncertainty Δϕ induced by the apertures. We demonstrate that the degradation of entanglement follows a universal law parametrised by the product l0Δϕ alone.

Purification of the residual entanglement.

Entanglement purification is an indispensable ingredient in extended quantum communication networks and usually determines the efficiency and communication rate of quantum communication protocols. Different from all existing entanglement purification protocols (EPPs) where two or more copies of low quality mixed entangled states are selected from the same ensemble, here we describe a general and optimal EPP for arbitrary initial mixed states from different ensembles. We show that the successful operation of EPP may not obtain a higher fidelity mixed state, while the discarded source pair, which is usually regarded as a failure in existing EPPs, may have residual entanglement and can be reused to increase the yield of entanglement purification. We give the criterions of both the successful purification to obtain a higher fidelity mixed state and the existence of residual entanglement. Moreover, we reveal that entanglement purification procedure causes some entanglement loss. Finally, we provide an optimal approach to reduce the entanglement loss. This approach can also be used to increase the yield of entanglement purification. Our EPP may have potential application in long-distance quantum communications.

Individual Molecular Dynamics of an Entangled Polyethylene Melt Undergoing Steady Shear Flow: Steady-State and Transient Dynamics.

The startup and steady shear flow properties of an entangled, monodisperse polyethylene liquid (C1000H2002) were investigated via virtual experimentation using nonequilibrium molecular dynamics. The simulations revealed a multifaceted dynamical response of the liquid to the imposed flow field in which entanglement loss leading to individual molecular rotation plays a dominant role in dictating the bulk rheological response at intermediate and high shear rates. Under steady shear conditions, four regimes of flow behavior were evident. In the linear viscoelastic regime (), orientation of the reptation tube network dictates the rheological response. Within the second regime (), the tube segments begin to stretch mildly and the molecular entanglement network begins to relax as flow strength increases; however, the dominant relaxation mechanism in this region remains the orientation of the tube segments. In the third regime (), molecular disentangling accelerates and tube stretching dominates the response. Additionally, the rotation of molecules become a significant source of the overall dynamic response. In the fourth regime (), the entanglement network deteriorates such that some molecules become almost completely unraveled, and molecular tumbling becomes the dominant relaxation mechanism. The comparison of transient shear viscosity, , with the dynamic responses of key variables of the tube model, including the tube segmental orientation, , and tube stretch, , revealed that the stress overshoot and undershoot in steady shear flow of entangled liquids are essentially originated and dynamically controlled by the component of the tube orientation tensor, rather than the tube stretch, over a wide range of flow strengths.

Ordering and Crystallization of Entangled Polyethylene Melts under Uniaxial Tension: A Molecular Dynamics Study

Morphological and mechanical properties of semicrystalline polymers are strongly influenced by flow-induced crystallization during processing. We perform extensive molecular dynamics simulations with more than 1 million atoms to describe orientation, drawability, and crystallization of entangled polyethylene melts under uniaxial tensions at three different strain rates and after a subsequent cooling. During tensile deformation at the lowest strain rate of 107 s–1, the polyethylene melt experiences entanglement loss and crystal nucleation. At higher strain rates of 108 and 109 s–1, we observe a higher degree of chain alignment and void formation in addition to disentanglement and crystal nucleation. Chain segments make sharp turns relative to the neighboring chain orientations at the entanglement points, which manifests as a bimodal distribution of the local order parameter. Upon cooling below the melting temperature, semicrystalline polyethylene with a crystallinity close to 50% is formed. The entanglemen...

Entanglement loss in molecular quantum-dot qubits due to interaction with the environment

We study quantum entanglement loss due to environmental interaction in a condensed matter system with a complex geometry relevant to recent proposals for computing with single electrons at the nanoscale. We consider a system consisting of two qubits, each realized by an electron in a double quantum dot, which are initially in an entangled Bell state. The qubits are widely separated and each interacts with its own environment. The environment for each is modeled by surrounding double quantum dots placed at random positions with random orientations. We calculate the unitary evolution of the joint system and environment. The global state remains pure throughout. We examine the time dependence of the expectation value of the bipartite Clauser–Horne–Shimony–Holt (CHSH) and Brukner–Paunković–Rudolph–Vedral (BPRV) Bell operators and explore the emergence of correlations consistent with local realism. Though the details of this transition depend on the specific environmental geometry, we show how the results can be mapped on to a universal behavior with appropriate scaling. We determine the relevant disentanglement times based on realistic physical parameters for molecular double-dots.

Entanglements in Glassy Polymer Crazing: Cross-Links or Tubes?

Models of the mechanical response of glassy polymers commonly assume that entanglements inherited from the melt act like chemical cross-links. The predictions from these network models and the physical picture they are based on are tested by following the evolution of topological constraints in simulations of model polymer glasses. The same behavior is observed for polymers with entanglement lengths Ne that vary by a factor of 3. A prediction for the craze extension ratio Λ based on the network model describes trends with Ne, but polymers do not have the taut configurations it assumes. There is also no evidence of the predicted geometrically necessary entanglement loss. While the number of entanglements remains constant, the identity of the chains forming constraints changes. The same relation between the amount of entanglement exchange and nonaffine displacement of monomers is found for crazing and thermal diffusion in end-constrained melts. In both cases, about 1/3 of the constraints change when monomer...