Entanglement Dynamics Research Articles

Criticality and entanglement in nonunitary quantum circuits and tensor networks of noninteracting fermions

Entanglement dynamics in nonunitary quantum systems have been found to exhibit novel nonequilibrium quantum phase transitions and have attracted tremendous attention with connections to various aspects of quantum information theory. This work establishes, for systems of noninteracting fermions, an exact three-way correspondence between (i) nonunitary (as well as unitary) quantum circuits dynamics in $d$ spatial dimensions; (ii) ($d$+1)-dimensional Gaussian tensor networks, and (iii) fermion systems in ($d$+1) spatial dimensions subject to unitary evolution with static Hamiltonians. Through this correspondence, $d$-dimensional random quantum circuits are connected with the classic subject area of Anderson localization in ($d$+1) spatial dimensions and consequently follow the ``tenfold way'' Altland-Zirnbauer classification. Selected examples of quantum circuits exhibiting entanglement phases and criticalities are used to illustrate these general principles.

F-deformed cavity mode coupled to a Λ-type atom in the presence of dissipation and Kerr nonlinearity

In this paper, the dynamics of a system consisting of a three-level atom, which interacts with a single-mode quantized field in a lossy cavity, is studied in the presence of the dependence of atom–field coupling and third-order nonlinear susceptibility on the intensity of light. The system contains a Λ -type atom coupled to a single-mode radiation field, with a degenerate multi-photon transition in the intensity-dependent regime. Also, the nonlinearity of the medium due to Kerr and intensity-dependent Kerr effects, and the detuning parameters are considered. Furthermore, to see the effects of dissipation such as photon absorption and scattering by the cavity mirrors and spontaneous emission of the atom, a non-Hermitian Hamiltonian is introduced, which results in obtaining the state vector of the whole system by applying the time-dependent Schrödinger equation. Thereupon, the dynamics of entanglement, coherence, photon statistics, and quadrature squeezing are numerically investigated. In each case, the roles of the intensity-dependent nonlinearity function, Kerr and intensity-dependent Kerr nonlinearity, different sources of dissipation, and detuning parameters are discussed. The numerical results indicate that the nonclassicality can remarkably be revealed, and can appropriately be controlled via the above-mentioned effects. It can be found that the presence of dissipation not only does not weaken the physical properties but also can enhance and protect the nonclassicality of the system.

Theorising health equity research for people with intersex variance through new materialism.

Health inequalities impact sex-variant people in highly differentiated ways. This is evidenced in much academic and activist intersex research documenting the highly specific forms of inequalities arising from misrecognition, discrimination and human rights abuses inherent to pathologised accounts of non-normative bodies. Important theoretical work further interrogates the implications of sex variant subjectivities, identities and bodies for static or binary notions of both sex and gender. In this paper, we aim to contribute further to this scholarship. We draw upon feminist materialist and Deleuzean-informed understandings of materials or matter to rethink debates over sex-variant subjectivities, identities and bodies in relation to inequalities in health. We argue 'the turn to matter' and associated new materialist theories draw attention to the complex, dynamic relational assemblages and entanglements mutually constituting the affective, embodied and socio-material worlds of intersex people. Informed by these theories, we propose that inequalities can be more fully addressed through a new health equity research agenda that is co-produced with sex-variant people. This agenda will enable a fuller exploration of the unsettling but transformative capacities of intersex matters and meanings with the contextually specific understandings of equity in relation to health and health care.

Entanglement and Charge-Sharpening Transitions in U(1) Symmetric Monitored Quantum Circuits

Monitored quantum circuits can exhibit an entanglement transition as a function of the rate of measurements, stemming from the competition between scrambling unitary dynamics and disentangling projective measurements. We study how entanglement dynamics in non-unitary quantum circuits can be enriched in the presence of charge conservation, using a combination of exact numerics and a mapping onto a statistical mechanics model of constrained hard-core random walkers. We uncover a charge-sharpening transition that separates different scrambling phases with volume-law scaling of entanglement, distinguished by whether measurements can efficiently reveal the total charge of the system. We find that while R\'enyi entropies grow sub-ballistically as $\sqrt{t}$ in the absence of measurement, for even an infinitesimal rate of measurements, all average R\'enyi entropies grow ballistically with time $\sim t$. We study numerically the critical behavior of the charge-sharpening and entanglement transitions in U(1) circuits, and show that they exhibit emergent Lorentz invariance and can also be diagnosed using scalable local ancilla probes. Our statistical mechanical mapping technique readily generalizes to arbitrary Abelian groups, and offers a general framework for studying dissipatively-stabilized symmetry-breaking and topological orders.

Effect of spacetime dimensions on quantum entanglement between two uniformly accelerated atoms

We investigate the entanglement dynamics for a quantum system composed of two uniformly accelerated Unruh-DeWitt detectors in different spacetime dimensions. It is found that the range of parameters in which entanglement can be generated is shrunk and the amount of generated entanglement is also decreased with the increasing spacetime dimension, by calculating the evolution of two-atom states using the method for open quantum systems. We study the entanglement evolution between two accelerated atoms for different initial two-atom states, and the influence of corresponding spacetime dimensions for every initial state is discussed. When the spacetime dimensions increase, the change of entanglement becomes slower with time. The influence of spacetime dimensions on the change of entanglement also expands to the case of the massive field. The time delay for entanglement generation is shown in different spacetime dimensions. In particular, entanglement decreases more quickly with the increasing spacetime dimensions compared with that in the case of the massless field. The recently found anti-Unruh effect is discussed, and a novel and interesting phenomenon is found that the Unruh effect in small spacetime dimensions can become the anti-Unruh effect in large spacetime dimensions with the same parameters.

Intertwiner entanglement excitation and holonomy operator

In the loop quantum gravity framework, spin network states carry entanglement between quantum excitations of the geometry at different space points. This intertwiner entanglement is gauge-invariant and comes from quantum superposition of spins and intertwiners. Bipartite entanglement can be interpreted as a witness of distance, while multipartite entanglement reflects the curvature of the quantum geometry. The present work investigates how the bipartite and multipartite intertwiner entanglement changes under the action of the holonomy operator, which is the basic building block of loop quantum gravity’s dynamics. We reveal the relation between entanglement excitation and the dispersion of the holonomy operator. This leads to a new interesting connection between bulk geometry and boundary observables via the dynamics of entanglement.

Teachers inquiring into translanguaging and multimodal pedagogies: emerging creative and critical entanglements during transnational professional development

ABSTRACT Our reflexive study responds to the need for learning about translanguaging and multimodality as entangled pedagogies in non-English-dominant contexts from teachers’ perspectives. This conceptual-empirical article re-examines a yearlong ethnographic study which traced how a community of seven in-service English language teachers in Colombia and the United States collaborated online and in person to make sense of and use translanguaging and multimodal pedagogies innovatively. Drawing on the notion of entanglements (assemblages of interconnections, events, people, practices, and resources that reveal tensions and translanguaging and multimodalities), we conceptualize them as enmeshed with social contexts. We ask, “What entanglements emerge when teachers implement translanguaging and multimodal pedagogies to enrich their practice in a context with inequitable access? Data sources include bilingual interviews, fieldnotes, and teacher-produced multimodal texts. We use dialogic reflexivity and vignettes to discuss teachers’ creation of new entanglements of translanguaging and multimodal pedagogies within the constraints of their setting. Emerging insights include 1) awareness of unequal access; 2) critical use of multimodalities and translanguaging for advocacy; 3) understandings of translanguaging and multimodalities for equitable access; and 4) translanguaging and multimodal pedagogies as creative, assemblages of interconnections, events, people, practices, and resources. These entangled pedagogies enabled teachers’ creativity and criticallity.

Integrable quenches in the Hubbard model

We study the quench dynamics of the one-dimensional Hubbard model through the quench action formalism. We introduce a class of integrable initial states—expressed as product states over two sites—for which we can provide an exact characterisation of the late-time regime. This is achieved by finding a closed-form expression for the overlaps between our states and the Bethe ansatz eigenstates, which we check explicitly in the limits of low densities and infinite repulsion. Our solution gives access to the stationary values attained by local observables (we show the explicit example of the density of doubly occupied sites) and the asymptotic entanglement dynamics directly in the thermodynamic limit. Interestingly, we find that for intermediate interaction strength Rényi entropies display a double-slope structure.

Bounds in nonequilibrium quantum dynamics

We review various bounds concerning out-of-equilibrium dynamics in few-level and many-body quantum systems. We primarily focus on closed quantum systems but will also mention some related results for open quantum systems and classical stochastic systems. We start from the speed limits, the universal bounds on the speeds of (either quantum or classical) dynamical evolutions. We then turn to review the bounds that address how good and how long would a quantum system equilibrate or thermalize. Afterward, we focus on the stringent constraint set by locality in many-body systems, rigorously formalized as the Lieb–Robinson bound. We also review the bounds related to the dynamics of entanglement, a genuine quantum property. Apart from some other miscellaneous topics, several notable error bounds for approximated quantum dynamics are discussed. While far from comprehensive, this topical review covers a considerable amount of recent progress and thus could hopefully serve as a convenient starting point and up-to-date guidance for interested readers.

Topological order and entanglement dynamics in the measurement-only XZZX quantum code

We examine the dynamics of a $(1+1)$-dimensional measurement-only circuit defined by the stabilizers of the [[5,1,3]] quantum error correcting code interrupted by single-qubit Pauli measurements. The code corrects arbitrary single-qubit errors and it stabilizes an area law entangled state with a ${D}_{2}={\mathbb{Z}}_{2}\ifmmode\times\else\texttimes\fi{}{\mathbb{Z}}_{2}$ symmetry protected topological (SPT) order, as well as a symmetry breaking (SB) order from a twofold bulk degeneracy. The Pauli measurements break the topological order and induce a phase transition into a trivial area law phase. Allowing more than one type of Pauli measurement increases the measurement-induced frustration and the SPT and SB order can be broken either simultaneously or separately at nonzero measurement rate. This yields a rich phase diagram and unanticipated critical behavior at the phase transitions. Although the correlation length exponent $\ensuremath{\nu}=\frac{4}{3}$ and the dynamical critical exponent $z=1$ are consistent with bond percolation, the prefactor of the logarithmic entanglement growth may take noninteger multiples of the percolation value. Remarkably, we identify a robust transient scaling regime for the purification dynamics of $L$ qubits. It reveals a modified dynamical critical exponent ${z}^{*}\ensuremath{\ne}z$, which is observable up to times $t\ensuremath{\sim}{L}^{{z}^{*}}$ and is reminiscent of the relaxation of critical systems into a prethermal state.

Suppressing the entanglement growth in matrix product state evolution of quantum systems through nonunitary similarity transformations

The possibility of using similarity transformations to alter dynamical entanglement growth in matrix-product-state simulations of quantum systems is explored. By appropriately choosing the similarity transformation, the entanglement growth rate is suppressed, improving the efficiency of numerical simulations of quantum systems. The transformation can be applied to general quantum-many-body systems.

Effects of Kaplan-Shekhtman-Entin-Wohlman-Aharony interactions on the non-markovian dynamics of quantum entanglement and communication

By using the non-Markovian Quantum State Diffusion method, the non-Markovian dynamics of entanglement, quantum dense coding and quantum teleportation in the spin chain system with Kaplan-Shekhtman-Entin-wohlman-Aharony interactions and Dzyaloshinskii-Moriya in- teractions are studied. In particular, the joint effects of Kaplan-Shekhtman-Entin-wohlman-Aharony interactions and different external magnetic fields are discussed under zero and finite temperatures, respectively. The results show that the concurrence, channel capacity of quantum dense coding and average fidelity of quantum teleportation can be effectively increased via the increasing of Kaplan-Shekhtman-Entin-wohlman-Aharony interactions along the z-direction which can be attributed to the constructive role of Kaplan-Shekhtman-Entin-wohlman-Aharony interactions on the O(3) invariance in the spin chain. Non-uniform magnetic fields with the combination of Kaplan-Shekhtman-Entin-wohlman-Aharony interactions are found to be more effective in the increasing of the parameters under discussion.

A thermodynamically-based constitutive theory for amorphous glassy polymers at finite deformations

In this work, a fully thermomechanical coupling constitutive theory is developed for amorphous glassy polymers to explain and predict their complex temperature- and rate-related nonlinear behavior during finite deformations. The foundation for the theory is the original kinematic and thermodynamic framework derived by Bouvard et al. (2013), in which internal state variables with clear physical significance are applied to describe the deformation mechanism of polymers. In contrast to the viewpoint of Bouvard et al. (2013), in the proposed model, we further divide the entanglements into two kinds of molecular microstructures, “permanent entanglements” and “dynamic entanglements”, and describe how their evolution during deformation is regarded as the internal mechanism for the material's macroscopic mechanical properties. Further, a series of new constitutive equations related to “dynamic entanglements” are proposed, which account for the strain softening caused by the dissociation of “dynamic entanglements”, reflect the influence of temperature on the dissociation rate of “dynamic entanglements” and include the effect of rate-dependent glass transition temperature (θg) on the microstructure. The equations related to “permanent entanglements” are also illustrated, which are improved based on the the work of Ames et al. (2009). The predictive capacity of the proposed thermomechanical coupling constitutive theory has been numerically realized by writing a user subroutine for finite element program. Taking polycarbonate (PC) as an example, the simulations are compared with experimental results for compression, shear, tension, and creep at different temperatures and strain rates. It is demonstrated that our proposed constitutive model with a more detailed physical meaning can well reproduce nonlinearity before yield, yield peak, strain softening, hardening and unloading behavior for amorphous glassy polymers under different stress states.

The Concept of Liminality as a Theoretical Tool in Literary Memory Studies: Liminal Aspects of Memory in Salman Rushdie’sMidnight’s Children

The Concept of Liminality as a Theoretical Tool in Literary Memory Studies<b>: Liminal Aspects of Memory in Salman Rushdie’s</b><b><i>Midnight’s Children</i></b>

Experimental verification of a coherence factorization law for quantum states

As a quantum resource, quantum coherence plays an important role in modern physics. Many coherence measures and their relations with entanglement have been proposed, and the dynamics of entanglement has been experimentally studied. However, the knowledge of general results for coherence dynamics in open systems is limited. Here we propose a coherence factorization law that describes the evolution of coherence passing through any noisy channels characterized by genuinely incoherent operations. We use photons to implement the quantum operations and experimentally verify the law for qubits and qutrits. Our work is a step toward understanding of the evolution of coherence when the system interacts with the environment, and will boost the study of more general laws of coherence.

Entanglement dynamics of a hard-core quantum gas during a Joule expansion

We study the entanglement dynamics of a one-dimensional hard-core quantum gas initially confined in a box of size L with saturated density ρ = 1. The gas is suddenly released into a region of size 2L by moving one of the box edges. We show that the analytic prediction for the entanglement entropy obtained from quantum fluctuating hydrodynamics holds quantitatively true even after several reflections of the gas against the box edges. We further investigate the long time limit t/L ≫ 1 where a Floquet picture of the non-equilibrium dynamics emerges and hydrodynamics eventually breaks down.

Protecting quantum entanglement in thermal reservoir by detuning

In this work, the quantum entanglement dynamics of a two-atom system in the thermal reservoir is investigated. An analytical solution of the single atom in the thermal reservoir and the expression of the quantum entanglement of the two-atom system in the thermal reservoir are obtained by the Markovian master equation method. The results showed that the nonzero temperature leads to sudden death of entanglement under the weak coupling limit. The higher the temperature, the faster the decay of entanglement. In particular, the detuning and the smaller spectrum width in the weak atom-reservoir coupling regime can effectively protect the quantum entanglement of the two-atom system in the thermal reservoir under the weak atom-reservoir coupling regime. The corresponding physical explanation is given by the entropy production rare.

Comparative study of the dynamics of quantum entanglement, purity and degree of purity in two hybrid quantum systems: non-Markovian and Markovian regime

Comparative study of the dynamics of quantum entanglement, purity and degree of purity in two hybrid quantum systems: non-Markovian and Markovian regime

Dynamics of entanglement in coherent states, entangled SchrÖdinger cat state and distribution function

We exploit the dynamics of entangled system between a harmonic oscillator and a single mode electromagnetic field as two harmonic oscillators, to examine quantum entanglement in coherent states. Through the Schrödinger cat state, we compute analytically its distribution function. Then, we check graphically the evolution of entanglement and the distribution function for two particular cases: the first is defined by two harmonic oscillators in quantum motion in a Paul trap; here whatever the quantum state , the system is at most entangled. The second case is visualised by two harmonic oscillators with a perturbative force, in that case, by varying the displacement numbers of the coherent states, the quantum entanglement and the distribution function present a similar evolution and they reach very large values. Comparing the two models: in the first, the dynamics of quantum entanglement exhibits a multi-frequency lines behaviour while in the second model, it shows an exponential behaviour.

GENERATION AND ROBUSTNESS OF QUANTUM MEMORY-ASSISTED ENTROPIC UNCERTAINTY AND UNCERTAINTY-INDUCED NONLOCALITY OF TWO NITROGEN-VACANCY CENTERS COUPLED BY OPEN TWO NANOCAVITIES

In this paper, we investigate the dynamics of quantum memory-assisted entropic uncertainty, uncertainty-induced nonlocality and log-negativity entanglement of two nitrogen-vacancy centers (NVC). In particular, we are interested in analyzing two nitrogen-vacancy centered qubits coupled with two coherent nanocavities. We consider two different configurations of NVC qubits: when the qubits are prepared initially in separable and maximally entangled states. We demonstrate that coherent nanocavities can be successfully used to generate nonlocality and entanglement in the two NVC qubits while suppressing the associated entropic uncertainty. When the system is considered initially in separable two-NVC qubits, we show that the coupled coherent nanocavities successfully generate nonlocality and entanglement while avoiding the associated entropic uncertainty. The parameter’s adjustment determines the degree of entanglement, non-locality generation, and preservation. In comparison, we find entanglement more vulnerable to the decoherence and entropic uncertainty action between the two NVC qubits and nanocavities than the uncertainty-induced nonlocality. Furthermore, the NVC-qubits coupled with two coherent nanocavities promote entanglement’s sudden birth and death phenomena. This study contributes to the quantum mechanical protocols requiring the robust practical generation of entanglement and nonlocality as well as the related information preservation for the increased efficiency of quantum devices.