Increased Fidelity via Quantum-Correlated X-Rays: IF via QCX Project #: 22-160 Year 1 of 3
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Characterization of the quantumness of unsteerable tripartite correlations
Quantumness for a bipartite unsteerable quantum correlation is operationally characterized by the notion of super-unsteerability. Super-unsteerability refers to the requirement of a larger dimension of the random variable that the steering party has to preshare with the party to be steered in the classical simulation protocol to generate an unsteerable correlation than the local Hilbert space dimension of the quantum states (reproducing the given unsteerable correlation) at the steering party’s side. In the present study, this concept of super-unsteerability is generalized by defining the notion of super-bi-unsteerability for tripartite correlations, which is unsteerable across a bipartite cut. Genuine super-bi-unsteerability is defined as the occurrence of super-bi-unsteerability across all possible bipartite cuts. Specific example of genuine super-bi-unsteerability for tripartite correlations has been presented. This study provides a tool to characterize the genuine quantumness of tripartite quantum correlations which are unsteerable across every bipartite cut.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Statistical Correlation Between Quantum Entanglement and Spin–Orbit Coupling in Crossed Beam Molecular Dynamics
Non-classical features like interference are already being harnessed to control the output of chemical reactions. However, quantum entanglement which is an equally enigmatic many-body quantum correlation can also be used as a powerful resource yet has eluded explicit attention. In this report, an experimental scheme under the crossed beam molecular dynamical setup, with the F + HD reaction, is proposed aiming to study the possible influence of entanglement within reactant pairs on the angular features of the product distribution. The aforesaid reaction has garnered interest recently, as an unusual horseshoe shape pattern in the product (HF) distribution was observed, which has been attributed to the coupling of spin and orbital degrees of freedom. An experimental scheme is proposed aiming to study the possible influence of entanglement on the necessity for the inclusion of such spin–orbit characteristics, under circumstances wherein the existence of entanglement and spin–orbit interaction is simultaneously detectable. The attainable results are further numerically simulated highlighting specific patterns corresponding to various possibilities. Finally, such studies if extended can provide unforeseen mechanistic insight into analogous reactions, too, from the lens of quantum information.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
CP symmetry and thermal effects on Dirac bi-spinor spin–parity local correlations
Intrinsic quantum correlations supported by the SU(2)ⓍSU(2) structure of the Dirac equation used to describe particle/antiparticle states, optical ion traps and bilayer graphene are investigated and connected to the description of local properties of Dirac bi-spinors. For quantum states driven by Dirac-like Hamiltonians, quantum entanglement and geometric discord between spin and parity degrees of freedom – sometimes mapped into equivalent low energy internal degrees of freedom – are obtained. Such spin–parity quantum correlations and the corresponding nonlocal intrinsic structures of bi-spinor fermionic states can be classified in order to relate quantum observables to the (non)local behavior of these correlations. It is shown that free particle mixed states do not violate the Clauser–Horne–Shimony–Holt inequality: the correlations in such mixed bi-spinors, although quantum, can be reproduced by a suitable local hidden variable model. Additionally, the effects due to a non-minimal coupling to a homogeneous magnetic field, and to the inclusion of thermal effects are evaluated, and quantum correlations of associated quantum mixtures and of the thermal states are all quantified. The above-mentioned correlation quantifiers are then used to measure the influence of CP transformations on spin–parity quantum correlations, and our results show that quantum entanglement is invariant under CP transformations, although the geometric discord is highly sensitive to the CP symmetry.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Discord as a quantum resource for bi-partite communication
Coherent interactions that generate negligible entanglement can still exhibit unique quantum behaviour. This observation has motivated a search beyond entanglement for a complete description of all quantum correlations. Quantum discord is a promising candidate. Here, we experimentally demonstrate that under certain measurement constraints, discord between bipartite systems can be consumed to encode information that can only be accessed by coherent quantum interactions. The inability to access this information by any other means allows us to use discord to directly quantify this ‘quantum advantage’.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Global quantum discord and quantum phase transition in XY model
We study the relationship between the behavior of global quantum correlations and quantum phase transitions in XY model. We find that the two kinds of phase transitions in the studied model can be characterized by the features of global quantum discord (GQD) and the corresponding quantum correlations. We demonstrate that the maximum of the sum of all the nearest neighbor bipartite GQDs is effective and accurate for signaling the Ising quantum phase transition, in contrast, the sudden change of GQD is very suitable for characterizing another phase transition in the XY model. This may shed lights on the study of properties of quantum correlations in different quantum phases.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Quantum entanglement correlations in double quark PDFs
Methods from Quantum Information Theory are used to scrutinize quantum correlations encoded in the two-quark density matrix over light-cone momentum fractions x 1 and x 2 . A nonperturbative three quark model light-cone wavefunction predicts significant nonclassical correlations associated with the “entanglement negativity” measure for asymmetric and small quark momentum fractions. We perform one step of QCD scale evolution of the entire density matrix, not just its diagonal (dPDF), by computing collinearly divergent corrections due to the emission of a gluon. Finally, we present first qualitative numerical results for single-step scale evolution of quantum entanglement correlations in double quark PDFs. At a higher Q 2 scale, the nonclassical correlations manifest in the dPDF for nearly symmetric momentum fractions.
Entanglement in field theory↗
Sub‐Diffraction Correlation of Quantum Emitters and Local Strain Fields in Strain‐Engineered WSe 2 Monolayers
Strain-engineering in atomically thin metal dichalcogenides is a useful method for realizing single-photon emitters (SPEs) for quantum technologies. Correlating SPE position with local strain topography is challenging due to localization inaccuracies from the diffraction limit. Currently, SPEs are assumed to be positioned at the highest strained location and are typically identified by randomly screening narrow-linewidth emitters, of which only a few are spectrally pure. In this work, hyperspectral quantum emitter localization microscopy is used to locate 33 SPEs in nanoparticle-strained WSe 2 monolayers with sub-diffraction-limit resolution (≈30 nm) and correlate their positions with the underlying strain field via image registration. In this system, spectrally pure emitters are not concentrated at the highest strain location due to spectral contamination; instead, isolable SPEs are distributed away from points of peak strain with an average displacement of 240 nm. These observations point toward a need for a change in the design rules for strain-engineered SPEs and constitute a key step toward realizing next-generation quantum optical architectures.
2D material↗
Using quantum noise correlation analysis to measure ion temperature
Quantum noise correlation analysis was tested at the proof-of-concept level as a technique to measure ion temperature in a plasma. If eventually successful, this technique could enable a compact, inexpensive, and robust ion temperature diagnostic suitable for a burning plasma environment. Ion temperature is a key parameter determining the fusion performance of a burning plasma, as the fusion cross-section has a strong dependence on ion temperature. This ion temperature diagnostic would require only a small optical view of the plasma through a port to passively record impurity line emission. The instrumentation would be remote from the reactor behind the neutron and bio-shielding. The technique relies solely on quantum correlations of the photons emitted by a plasma impurity to measure ion temperature; there is no grating dispersion of an emission line-width or pulse-height analysis of photon energy. This measurement innovation was tested with instrumentation consisting of two single-photon detectors with high timing resolution, a time-tagging unit, and simple light collection optics. This instrumentation measures the second-order correlation between the light intensity falling on the two detectors. The next steps beyond the proof-of-concept level will be development of diagnostic designs for application of this technique to high-temperature and burning plasmas. Arrays of single-photon avalanche detectors to multiplex measurements of photon correlation will be required to reduce signal integration time to an acceptable duration.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Mitigating Scattering in a Quantum System Using Only an Integrating Sphere
Strong quantum correlated sources are essential but delicate resources for quantum information science and engineering protocols. Decoherence and loss are the two main disruptive processes that lead to the loss of nonclassical behavior in quantum correlations. In quantum systems, scattering can contribute to both decoherence and loss. In this work, we present an experimental scheme capable of significantly mitigating the adverse impact of scattering in quantum systems. Our quantum system is composed of a two-mode squeezed light generated with the four-wave-mixing process in hot rubidium vapor and a scatterer is introduced to one of the two modes. An integrating sphere is then placed after the scatterer to recollect the scattered photons. We use mutual information between the two modes as the measure of quantum correlations and demonstrate a 47.5% mutual information recovery from scattering, despite an enormous photon loss of greater than 85%. Our scheme is the very first step toward recovering quantum correlations from disruptive random processes and thus has the potential to bridge the gap between proof-of-principle demonstrations and practical real-world implementations of quantum protocols. Published by the American Physical Society 2024
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Parallel Quantum-Enhanced Sensing
Quantum metrology takes advantage of quantum correlations to enhance the sensitivity of sensors and measurement techniques beyond their fundamental classical limit, given by the shot-noise limit. The use of both temporal and spatial correlations present in quantum states of light can extend quantum-enhanced sensing to a parallel configuration that can simultaneously probe an array of sensors or independently measure multiple parameters. To this end, we use multispatial-mode bright twin beams of light, which are characterized by independent quantum-correlated spatial subregions in addition to quantum temporal correlations, to probe a four-sensor quadrant plasmonic array. We show that it is possible to independently and simultaneously measure local changes in refractive index for all four sensors with a quantum enhancement in sensitivity in the range of 22% to 24% over the corresponding classical configuration. Finally, these results provide a first step toward highly parallel spatially resolved quantum-enhanced sensing techniques and pave the way toward more complex quantum sensing and quantum imaging platforms.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Some properties of correlations of quantum lattice systems in thermal equilibrium
Simple proofs of uniqueness of the thermodynamic limit of KMS states and of the decay of equilibrium correlations are presented for a large class of quantum lattice systems at high temperatures. New quantum correlation inequalities for general Heisenberg models are described. Finally, a simplified derivation of a general result on power-law decay of correlations in 2D quantum lattice systems with continuous symmetries is given, extending results of McBryan and Spencer for the 2D classical XY model.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Detecting Quantum Critical Points of Correlated Systems by Quantum Convolutional Neural Network Using Data from Variational Quantum Eigensolver
Machine learning has been applied to a wide variety of models, from classical statistical mechanics to quantum strongly correlated systems, for classifying phase transitions. The recently proposed quantum convolutional neural network (QCNN) provides a new framework for using quantum circuits instead of classical neural networks as the backbone of classification methods. We present the results from training the QCNN by the wavefunctions of the variational quantum eigensolver for the one-dimensional transverse field Ising model (TFIM). We demonstrate that the QCNN identifies wavefunctions corresponding to the paramagnetic and ferromagnetic phases of the TFIM with reasonable accuracy. The QCNN can be trained to predict the corresponding ‘phase’ of wavefunctions around the putative quantum critical point even though it is trained by wavefunctions far away. The paper provides a basis for exploiting the QCNN to identify the quantum critical point.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Coherent exchange correlation in quantum systems
A number of exchange correlation effects in quantum systems are discussed from a unified point of view. These effects can be observed at both microscopic and macroscopic distances. The analysis of macroscopic correlation effects requires an understanding of the physical mechanism of exchange correlation. This, in turn, requires an analysis of the phase relationships between the wave functions of quantum states that determine the observed physical quantities. The neglect of these phase relationships in the interpretation of correlation experiments gave rise to assumptions such as instantaneous long-range interaction and other similar ideas that contradict the traditional physical principles of short-range interaction, causality, and locality. On the contrary, understanding the physical nature of the correlation mechanism makes it possible to explain these experiments without these kinds of ideas.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Landau diagrams in AdS and S-matrices from conformal correlators
Quantum field theories in AdS generate conformal correlation functions on the boundary, and in the limit where AdS is nearly flat one should be able to extract an S-matrix from such correlators. We discuss a particularly simple position-space procedure to do so. It features a direct map from boundary positions to (on-shell) momenta and thereby relates cross ratios to Mandelstam invariants. This recipe succeeds in several examples, includes the momentum-conserving delta functions, and can be shown to imply the two proposals in based on Mellin space and on the OPE data. Interestingly the procedure does not always work: the Landau singularities of a Feynman diagram are shown to be part of larger regions, to be called ‘bad regions’, where the flat-space limit of the Witten diagram diverges. To capture these divergences we introduce the notion of Landau diagrams in AdS. As in flat space, these describe on-shell particles propagating over large distances in a complexified space, with a form of momentum conservation holding at each bulk vertex. As an application we recover the anomalous threshold of the four-point triangle diagram at the boundary of a bad region.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Convergence and Quantum Advantage of Trotterized MERA for Strongly-Correlated Systems
Strongly-correlated quantum many-body systems are difficult to study and simulate classically. We recently proposed a variational quantum eigensolver (VQE) based on the multiscale entanglement renormalization ansatz (MERA) with tensors constrained to certain Trotter circuits. Here, we determine the scaling of computation costs for various critical spin chains which substantiates a polynomial quantum advantage in comparison to classical MERA simulations based on exact energy gradients or variational Monte Carlo. Algorithmic phase diagrams suggest an even greater separation for higher-dimensional systems. Hence, the Trotterized MERA VQE is a promising route for the efficient investigation of strongly-correlated quantum many-body systems on quantum computers. Furthermore, we show how the convergence can be substantially improved by building up the MERA layer by layer in the initialization stage and by scanning through the phase diagram during optimization. For the Trotter circuits being composed of single-qubit and two-qubit rotations, it is experimentally advantageous to have small rotation angles. We find that the average angle amplitude can be reduced considerably with negligible effect on the energy accuracy. Benchmark simulations suggest that the structure of the Trotter circuits for the TMERA tensors is not decisive; in particular, brick-wall circuits and parallel random-pair circuits yield very similar energy accuracies.
Miao, Qiang [Duke Quantum Center, Duke University,↗
One-norm geometric quantum discord and critical point estimation in the XY spin chain
In contrast with entanglement and quantum discord (QD), we investigate the thermal quantum correlation in terms of Schatten one-norm geometric quantum discord (GQD) in the XY spin chain, and analyze their capabilities in detecting the critical point of quantum phase transition. We show that the one-norm GQD can reveal more properties about quantum correlation between two spins, especially for the long-range quantum correlation at finite temperature. Under the influences of site distance, anisotropy and temperature, one-norm GQD and its first derivative make it possible to detect the critical point efficiently for a general XY spin chain. - Highlights: • Comparing with entanglement and QD, one-norm GQD is more robust versus the temperature. • One-norm GQD is more efficient in characterization of long-range quantum correlation between two distant qubits. • One-norm GQD performs well in highlighting the critical point of QPT at zero or low finite temperature. • One-norm GQD has a number of advantages over QD in detecting the critical point of the spin chain.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Site-resolved multiple-quantum filtered correlations and distance measurements by magic-angle spinning NMR: Theory and applications to spins with weak to vanishing quadrupolar couplings
We discuss and analyze four magic-angle spinning solid-state NMR methods that can be used to measure internuclear distances and to obtain correlation spectra between a spin I = 1/2 and a half-integer spin S > 1/2 having a small quadrupolar coupling constant. Three of the methods are based on the heteronuclear multiple-quantum and single-quantum correlation experiments, that is, high rank tensors that involve the half spin and the quadrupolar spin are generated. Here, both zero and single-quantum coherence of the half spins are allowed and various coherence orders of the quadrupolar spin are generated, and filtered, via active recoupling of the dipolar interaction. As a result of generating coherence orders larger than one, the spectral resolution for the quadrupolar nucleus increases linearly with the coherence order. Since the formation of high rank tensors is independent of the existence of a finite quadrupolar interaction, these experiments are also suitable to materials in which there is high symmetry around the quadrupolar spin. A fourth experiment is based on the initial quadrupolar-driven excitation of symmetric high order coherences (up to p = 2S, where S is the spin number) and subsequently generating by the heteronuclear dipolar interaction higher rank (l + 1 or higher) tensors that involve also the half spins. Due to the nature of this technique, it also provides information on the relative orientations of the quadrupolar and dipolar interaction tensors. For the ideal case in which the pulses are sufficiently strong with respect to other interactions, we derive analytical expressions for all experiments as well as for the transferred echo double resonance experiment involving a quadrupolar spin. We show by comparison of the fitting of simulations and the analytical expressions to experimental data that the analytical expressions are sufficiently accurate to provide experimental {sup 7}Li–{sup 13}C distances in a complex of lithium, glycine, and water. Discussion of the regime for which such an approach is valid is given.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗