Identical Particles Research Articles

Topology-induced quantum transition in multiparticle systems in vicinity of a black hole

The qualitative change of the type of particle trajectory homotopy in close vicinity of general-relativistic gravitational singularity affects quantum statistics in systems of identical indistinguishable particles at passing the photon sphere rim of a Schwarzschild black hole. This causes a local departure from the Pauli exclusion principle, which results in some high energy effects manifesting themselves when the matter is falling into a black hole. The release of the energy can take place at the rim of the photon sphere of a black hole due to the decay of Fermi spheres in highly compressed fermion systems entering this region. The effect is observable at activity of quasars or at collapses of neutron star mergers. The related supplementation to conventional models of the accretion disc luminosity by additional radiation from close vicinity of the event horizon of a massive black hole powering super-luminous quasar is proposed and compared with observations. The source of short-lasting gamma-ray bursts has been also identified at collapses of unstable neutron star mergers due to the decay of Fermi sphere of neutrons. The duration and spectrum of the related e-m radiation bursts estimated by the Fermi golden rule for the Fermi sphere decay agree with observations. The quantum statistics effect contributes also to the radiation of transients of micro-quasars and short lasting brightening episodes in closer active galactic nuclei. The proposed quantum effect changes the premises for the current discussion of the information paradox and hypothesis of the black hole firewall.

Indistinguishability-assisted two-qubit entanglement distillation

Production of quantum states exhibiting a high degree of entanglement out of noisy conditions is one of the main goals of quantum information science. Here, we provide a conditional yet efficient entanglement distillation method which functions within the framework of spatially localized operations and classical communication. This method exploits indistinguishability effects due to the spatial overlap between two identical qubits in distinct sites and encompasses particle statistics imprint. We derive the general conditions for the maximum entanglement distillation out of mixed states. As applications, we give a thorough description of distilled entanglement and associated success probability starting from typical noisy states, such as thermal Gibbs states and Werner states. The influence of local temperatures and of a noise parameter is discussed, respectively, in these two cases. The proposed scheme paves the way towards quantum repeaters in composite networks made of controllable identical quantum particles.

Bulk flow and correlation measurements at LHCb

Particle correlations are a powerful tool to study the properties of the bulk nuclear matter produced in relativistic heavy ion collisions. The momentum correlations between identical particles originating from the same particleemitting source, referred to as the Bose-Einstein correlations, measure scales that are related to the geometrical size of the source. The two-particle azimuthal angular correlations measure the spatial anisotropy of produced particles, providing information on collective phenomena arising in the dense nuclear medium. This contribution will discuss new LHCb measurements of Bose- Einstein correlations and, for the first time, the collective flow coefficients in the far forward rapidity region.

Bright photoluminescence from CdSe quantum dots conjugated with metal phthalocyanines

Engineering organic/inorganic nanohybrids is one of the emerging tracks in material science to search for new nanomaterials with tailored and/or enhanced properties. In this work, we report the synthesis of CdSe quantum dots (QDs) conjugated with selected metal phthalocyanine (MPc), e.g., ZnPc and CuPc, utilizing the hot-injection organometallic method. The prepared pristine and conjugated QD systems exhibit practically identical particle size and spherical morphology and feature the characteristic CdSe excitonic peaks in their optical absorption spectra. The successful incorporation of ZnPc or CuPc molecules is ensured by the appearance of their sharp Q-band peaks in the optical absorption and the Zn2p or Cu2p core levels in the X-ray photoemission spectroscopy (XPS) measurements. The pure CdSe QDs sample of selected size (∼4.0 nm) exhibits well-defined photoluminescence (PL) peak at the limit of the green range, which is remarkably enhanced for the conjugated QD systems, reaching ∼250 % for the CuPc/CdSe QDs. Such prominent PL enhancement is attributed to Förster resonance energy transfer stimulated by deep B-band emissions from CuPc molecules combined with charge transfer from MPc molecules to CdSe QDs. Furthermore, the emission is greatly amplified upon prolonged exposure to laser beam, exceeding 400 % of the initial CuPc/CdSe emission after only 40 min of exposure time, yet without significant changes in their emission color. Thus, these MPc/CdSe conjugated QD systems are promising nanomaterials for intense white light sources.

Permutationally Invariant Networks for Enhanced Sampling (PINES): Discovery of Multimolecular and Solvent-Inclusive Collective Variables.

The typically rugged nature of molecular free-energy landscapes can frustrate efficient sampling of the thermodynamically relevant phase space due to the presence of high free-energy barriers. Enhanced sampling techniques can improve phase space exploration by accelerating sampling along particular collective variables (CVs). A number of techniques exist for the data-driven discovery of CVs parametrizing the important large-scale motions of the system. A challenge to CV discovery is learning CVs invariant to the symmetries of the molecular system, frequently rigid translation, rigid rotation, and permutational relabeling of identical particles. Of these, permutational invariance has proved a persistent challenge in frustrating the data-driven discovery of multimolecular CVs in systems of self-assembling particles and solvent-inclusive CVs for solvated systems. In this work, we integrate permutation invariant vector (PIV) featurizations with autoencoding neural networks to learn nonlinear CVs invariant to translation, rotation, and permutation and perform interleaved rounds of CV discovery and enhanced sampling to iteratively expand the sampling of configurational phase space and obtain converged CVs and free-energy landscapes. We demonstrate the permutationally invariant network for enhanced sampling (PINES) approach in applications to the self-assembly of a 13-atom argon cluster, association/dissociation of a NaCl ion pair in water, and hydrophobic collapse of a C45H92 n-pentatetracontane polymer chain. We make the approach freely available as a new module within the PLUMED2 enhanced sampling libraries.

The exchange effect interference mechanisms in quantum mechanics

In quantum mechanics, there are two interference mechanisms between identical particles. One is that the de Broglie wavelengths of two interference waves are the same, which is called the equal wavelength interference mechanism. There have been many experiments by this mechanism. The other is that the wavelengths of interference waves can also be different, in which case there should be an exchange term in addition to the direct term in the wave function. There is a fixed phase difference between the two terms, which causes interference. This is called exchange effect interference mechanism. There is a special case where two interference waves can satisfy both the two mechanisms. We propose an experiment to discriminate that in this case which mechanism plays a role on earth. By the exchange effect interference mechanism, it is possible to construct artificial crystals and to study the physical properties of this kind of crystals.

Entanglement monogamy in indistinguishable particle systems

Recently, it has been realized that indistinguishability is a resource for quantum information processing. A new method to represent the indistinguishable particles by Franco et al. (Sci Rep 6:20603, 2016, https://doi.org/10.1038/srep20603) and measure the concurrence is developed by Nosrati et al. (npj Quantum Inf 6:39, 2020, https://doi.org/10.1038/s41534-020-0271-7). The monogamy property says that quantum entanglement cannot be shared freely between more than two particles. For three distinguishable particles, the monogamy of entanglement was first expressed as an inequality using squared concurrence where each particle has a single degree of freedom (for pure or mixed states). Using multiple degrees of freedom, similar inequality was shown to be held between two distinguishable particles. However, for two indistinguishable particles, where each particle cannot be addressed individually, the monogamy inequality was shown to be violated maximally for a specific state. Thus a question naturally arises: what happens to the monogamy of entanglement in the case of three or more indistinguishable particles? We prove that monogamy holds in this scenario and the inequality becomes equality for all pure indistinguishable states. Further, we provide three major operational meanings of our result. Finally, we present an experimental schematic using photons to observe our result.

Testing the braneworld theory with identical particles

Testing the braneworld theory with identical particles

Solving complex nanostructures with ptychographic atomic electron tomography

Transmission electron microscopy (TEM) is essential for determining atomic scale structures in structural biology and materials science. In structural biology, three-dimensional structures of proteins are routinely determined from thousands of identical particles using phase-contrast TEM. In materials science, three-dimensional atomic structures of complex nanomaterials have been determined using atomic electron tomography (AET). However, neither of these methods can determine the three-dimensional atomic structure of heterogeneous nanomaterials containing light elements. Here, we perform ptychographic electron tomography from 34.5 million diffraction patterns to reconstruct an atomic resolution tilt series of a double wall-carbon nanotube (DW-CNT) encapsulating a complex ZrTe sandwich structure. Class averaging the resulting tilt series images and subpixel localization of the atomic peaks reveals a Zr11Te50 structure containing a previously unobserved ZrTe2 phase in the core. The experimental realization of atomic resolution ptychographic electron tomography will allow for the structural determination of a wide range of beam-sensitive nanomaterials containing light elements.

The two-qubit singlet/triplet measurement is universal for quantum computing given only maximally-mixed initial states.

In order to delineate which minimalistic physical primitives can enable the full power of universal quantum computing, it has been fruitful to consider various measurement based architectures which reduce or eliminate the use of coherent unitary evolution, and also involve operations that are physically natural. In this context previous works had shown that the triplet-singlet measurement of two qubit angular momentum (or equivalently two qubit exchange symmetry) yields the power of quantum computation given access to a few additional different single qubit states or gates. However, Freedman, Hastings and Shokrian-Zini1 recently proposed a remarkable conjecture, called the 'STP=BQP' conjecture, which states that the two-qubit singlet/triplet measurement is quantum computationally universal given only an initial ensemble of maximally mixed single qubits. In this work we prove this conjecture. This provides a method for quantum computing that is fully rotationally symmetric (i.e. reference frame independent), using primitives that are physically very-accessible, naturally resilient to certain forms of error, and provably the simplest possible.

Algebrodynamics: Shear-Free Null Congruences and New Types of Electromagnetic Fields

We briefly present our version of noncommutative analysis over matrix algebras, the algebra of biquaternions (B) in particular. We demonstrate that any B-differentiable function gives rise to a null shear-free congruence (NSFC) on the B-vector space CM and on its Minkowski subspace M. Making use of the Kerr–Penrose correspondence between NSFC and twistor functions, we obtain the general solution to the equations of B-differentiability and demonstrate that the source of an NSFC is, generically, a world sheet of a string in CM. Any singular point, caustic of an NSFC, is located on the complex null cone of a point on the generating string. Further we describe symmetries and associated gauge and spinor fields, with two electromagnetic types among them. A number of familiar and novel examples of NSFC and their singular loci are described. Finally, we describe a conservative algebraic dynamics of a set of identical particles on the “Unique Worldline” and discuss the connections of the theory with the Feynman–Wheeler concept of “One-Electron Universe”.

Modeling the structure and thermodynamics of multicomponent and polydisperse hard-sphere dispersions with continuous potentials.

A model system of identical particles interacting via a hard-sphere potential is essential in condensed matter physics; it helps to understand in and out of equilibrium phenomena in complex fluids, such as colloidal dispersions. Yet, most of the fixed time-step algorithms to study the transport properties of those systems have drawbacks due to the mathematical nature of the interparticle potential. Because of this, mapping a hard-sphere potential onto a soft potential has been recently proposed [Báez et al., J. Chem. Phys. 149, 164907 (2018)]. More specifically, using the second virial coefficient criterion, one can set a route to estimate the parameters of the soft potential that accurately reproduces the thermodynamic properties of a monocomponent hard-sphere system. However, real colloidal dispersions are multicomponent or polydisperse, making it important to find an efficient way to extend the potential model for dealing with such kind of many-body systems. In this paper, we report on the extension and applicability of the second virial coefficient criterion to build a description that correctly captures the phenomenology of both multicomponent and polydisperse hard-sphere dispersions. To assess the accuracy of the continuous potentials, we compare the structure of soft polydisperse systems with their hard-core counterpart. We also contrast the structural and thermodynamic properties of soft binary mixtures with those obtained through mean-field approximations and the Ornstein-Zernike equation for the two-component hard-sphere dispersion.

Accessing inaccessible information via quantum indistinguishability

In this paper we present and analyze an information-theoretic task that consists in learning a bit of information by spatially moving the ‘target’ particle that encodes it. We show that, on one hand, the task can be solved with the use of additional independently prepared quantum particles, only if these are indistinguishable from the target particle. On the other hand, the task can be solved with the use of distinguishable quantum particles, only if they are entangled with the target particle. Our task thus provides a new example in which the entanglement apparently inherent to independently prepared indistinguishable quantum particles is put into use for information processing. Importantly, a novelty of our protocol lies in that it does not require any spatial overlap between the involved particles. Besides analyzing the class of quantum-mechanical protocols that solve our task, we gesture towards possible ways of generalizing our results and of applying them in cryptography.

The non-Wiener dynamics of an ensemble of identical anharmonic oscillators

The model of an ensemble of anharmonic oscillators in the field of a common broadband photon-free thermostat is reduced to a model of an ensemble of identical N-level particles in terms of the algebraic perturbation theory. In one region the model describes the Dicke superadiance, and in the other one—oscillating dependence of the collective radiation intensity on the number of the ensemble oscillator. The collective radiation proves to be suppressed with a certain number of oscillators.

Environmental exposure more than plastic composition shapes marine microplastic-associated bacterial communities in Pacific versus Caribbean field incubations.

Microplastics have arisen as a global threat to marine ecosystems. In this study, we explored the role that plastic polymer type, incubation time and geographic location have on shaping the microbial community adhered to the microplastics, termed the plastisphere. We performed detailed bacterial plastisphere community analyses on microplastics of six different household plastic polymers, serving as proxies of secondary microplastics, incubated for 6 weeks in coastal Pacific waters. These bacterial communities were compared to the plastisphere communities grown on identical microplastic particles incubated in the coastal Caribbean Sea at Bocas del Toro, Panama. Ribosomal gene sequencing analyses revealed that bacterial community composition did not exhibit a significant preference for plastic type at either site but was instead driven by the incubation time and geographic location. We identified a 'core plastisphere' composed of 57 amplicon sequence variants common to all plastic types, incubation times and locations, with possible synergies between taxa. This study contributes to our understanding of the importance of geography in addition to exposure time, in the composition of the plastisphere.

Dependence of pore space structure and characteristics of SiC-based ceramic materials on the morphology of the initial components

Ultrafine silicon carbide powders of two types were used as fillers for synthesis of porous ceramics. The first powder was obtained by the furnace method (SiCF), the second sample was synthesized using the SHS technology (SiCSHS). The fillers had identical average particle size, but different morphology of their surface. It is established that with the same size, the morphology of initial powder components determined structural parameters and characteristics of the synthesized porous ceramics. It determines effective applicability of various materials for ultrafiltration or catalysis processes.

Fermionic physics from abinitio path integral Monte Carlo simulations of fictitious identical particles.

The abinitio path integral Monte Carlo (PIMC) method is one of the most successful methods in statistical physics, quantum chemistry and related fields, but its application to quantum degenerate Fermi systems is severely hampered by an exponential computational bottleneck: the notorious fermion signproblem. Very recently, Xiong and Xiong [J. Chem. Phys. 157, 094112 (2022)] have suggested to partially circumvent the signproblem by carrying out simulations of fictitious systems guided by an interpolating continuous variable ξ ∈ [-1, 1], with the physical Fermi- and Bose-statistics corresponding to ξ = -1 and ξ = 1. It has been proposed that information about the fermionic limit might be obtained by calculations within the bosonic sector ξ > 0 combined with an extrapolation throughout the fermionic sector ξ < 0, essentially bypassing the signproblem. Here, we show how the inclusion of the artificial parameter ξ can be interpreted as an effective penalty on the formation of permutation cycles in the PIMC simulation. We demonstrate that the proposed extrapolation method breaks down for moderate to high quantum degeneracy. Instead, the method constitutes a valuable tool for the description of large Fermi-systems of weak quantum degeneracy. This is demonstrated for electrons in a 2D harmonic trap and for the uniform electron gas (UEG), where we find excellent agreement (∼0.5%) with exact configuration PIMC results in the high-density regime while attaining a speed-up exceeding 11 orders of magnitude. Finally, we extend the idea beyond the energy and analyze the radial density distribution (2D trap), as well as the static structure factor and imaginary-time density-density correlation function (UEG).

Physical, chemical, electronic and optical properties of CuO/NiO@n-Si thin films by drop casting method for p–n junction diode

The development of photodetector technology is the outcome of diverse research in materials science, device engineering, and manufacturing methods. Hence, we synthesized p-CuO@n-Si, p-NiO@n-Si, p-CuO/NiO@n-Si and p-CuO/NiO-TX-100@n-Si Schottky Barrier diodes by drop-casting method and characterized by XRD, SEM, EDX, TEM, XPS and UV–visible. From the XRD analysis, the pure p-CuO@n-Si and p-NiO@n-Si, found to exhibit monoclinic and cubic crystal structure respectively whereas p-CuO/NiO@n-Si and p-CuO/NiO-TX-100@n-Si exhibits missing of two phases. The SEM images pure p-CuO@n-Si particle structure is cluster but, in contrast the pure p-NiO@n-Si exhibit spherical shape with identical particle. The Triton X-100 blend with CuO/NiO resulting the reduction of particle size in between 20 and 40 nm for p-CuO/NiO-TX-100@n-Si confirmed by TEM analysis. The photo-response characteristics of p-CuO/NiO-TX-100@n-Si Schottky barrier diode exhibit minimum ideality factor (n) (2.64), maximum barrier height (ΦB) (0.78 eV), maximum photosensitivity (Ps) ∼ 6.62 × 102%, photoresponsivity (R) ∼ 598.61 mA/W, external quantum efficiency (EQE)∼ 325.75 %, and specific detectivity (D*) ∼ 11.08 × 1012 (Jones) when compared other diodes.

Quadratic scaling bosonic path integral molecular dynamics.

Bosonic exchange symmetry leads to fascinating quantum phenomena, from exciton condensation in quantum materials to the superfluidity of liquid 4He. Unfortunately, path integral molecular dynamics (PIMD) simulations of bosons are computationally prohibitive beyond ∼100 particles, due to a cubic scaling with the system size. We present an algorithm that reduces the complexity from cubic to quadratic, allowing the first simulations of thousands of bosons using PIMD. Our method is orders of magnitude faster, with a speedup that scales linearly with the number of particles and the number of imaginary time slices (beads). Simulations that would have otherwise taken decades can now be done in days. In practice, the new algorithm eliminates most of the added computational cost of including bosonic exchange effects, making them almost as accessible as PIMD simulations of distinguishable particles.

Scattering of identical particles by a one-dimensional Dirac delta function barrier potential: The role of statistics

Scattering of non-interacting, identical bosons or fermions by a one-dimensional Dirac delta function barrier potential underlines the importance of the role of statistics (that is, whether the particles obey Fermi–Dirac or Bose–Einstein statistics) in the scattering. We consider an initial wave function for the system that corresponds to one particle incident from the left and one from the right of the potential barrier. For bosons, both particles are scattered either to the left or to the right if the intensity reflection coefficient is 1/2, provided the left and right propagating wave packets fully overlap in the scattering region. For fermions, the particles “pass through” one another, provided the left and right propagating wave packets fully overlap in the scattering region, with zero probability that both particles are scattered to the left or right, consistent with the Pauli exclusion principle.