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Rongchao Ma

Publications and source records attributed to Rongchao Ma.

15 recordsLinked to original sources

Symmetry Packaging II: A Group-Theoretic Framework for Packaging Under Finite, Compact, Higher-Form, and Hybrid Symmetries

Symmetry packaging is the phenomenon whereby, upon particle creation, all the internal quantum numbers (IQNs) become locked into a single irreducible representation (irrep) block of the gauge group, as required by locality and gauge invariance. The resulting packaged quantum states exhibit characteristic symmetry constraints and entanglement patterns. We develop a group-theoretic framework to describe the symmetry packaging for a variety of concrete symmetries and to classify the corresponding packaged states: \textbf{(1)} We prove that for any finite or compact group $G$, there exist $G$-associated packaged subspaces, in which every vector is automatically a packaged state. In particular, in multi-particle systems, any nontrivial representation of $G$ induces inseparable packaged entanglement that locks together all IQNs. \textbf{(2)} We apply this framework to symmetry packaging in finite groups (cyclic group $\mathbb{Z}_N$, charge conjugation $C$, fermion parity, parity $P$, time reversal $T$, and dihedral groups), compact groups ($\mathrm{U}(1)$, $\mathrm{SU}(N)$, $\mathrm{SU}(2)$, and $\mathrm{SU}(3)$), $p$-form symmetries, and hybrid symmetries. In each case, gauge invariance and superselection rules forbid the factorization of the resulting states. We illustrate how Bell-type packaged entangled states, color confinement, and hybrid gauge-invariant configurations all arise naturally. These results yield a complete classification of packaged quantum states. \textbf{(3)} Finally, we extend the packaging principle to incorporate full spacetime symmetry and hybrid systems of local, global, and Lorentz/Poincaré charges. Our approach unifies tools from group theory, gauge theory, and topological classification. These results may be useful for potential applications in high energy physics, quantum field theory, and quantum technologies.

hep-th

Symmetry Packaging I: Irreducible Representation Blocks, Superselection, and Packaged Entanglement in Quantum Field Theory

We introduce the concept of symmetry packaging for quantum field excitations: in a quantum field theory with a gauge group $G$, every local creation operator carries its full set of internal quantum numbers (IQNs) as a single irreducible $G$-block and forbids any partial factorization. We elevate this observation to a symmetry packaging principle, which asserts that packets of IQNs remain intact throughout all physical processes. We analyze a quantum-field excitation in six successive stages: (1) particle creation/annihilation, (2) hybridization with gauge-blind external degrees of freedom (DOFs), (3) tensor-product assembly, (4) isotypic decomposition, (5) packaged superposition/entanglement, and (6) local Gauge-Invariance constraint. We show that packaging survives every stage and culminates in a gauge-invariant physical Hilbert space. These stages unfold within a three packaging layer hierarchy (raw-Fock $\to$ isotypic $\to$ physical) with distinct packaging characters. Packaging alone reproduces familiar charge-superselection rules and, within any fixed-charge sector, admits a new class of packaged entangled states where internal and external DOFs are inseparably locked. We derive necessary and sufficient conditions for such superpositions and show that packaged irreps behave as noise-protected logical qudits. This framework unifies representation theory, superselection, and entanglement under a single mathematical roof and provides a roadmap for constructing and manipulating packaged states in any gauge theory.

hep-th

Packaged Quantum States for Gauge-Invariant Quantum Computation and Communication

Packaged quantum states are gauge-invariant states in which all internal quantum numbers (IQNs) form an inseparable block. This feature gives rise to novel packaged entanglements that encompass all IQNs, which is important both for fundamental physics and for quantum technology. Here we develop a framework for gauge-invariant quantum information processing based on packaged quantum states. We propose the necessary and sufficient conditions for a valid packaged superposition state of a single particle and multi-particle. We then present the details of constructing gauge-invariant packaged qubits (or qudits), packaged gates, and packaged circuits (which commute with the total charge operator). These serve as alternative foundation for gauge-invariant quantum information science. We then adapt conventional quantum error-correction codes, quantum algorithms, and quantum communication protocols to the ($d \times D$)-dimensional hybrid-packaged subspace. This high-dimensional hybrid-packaged subspace is flexible for pruning and scaling to match available physics systems. Thus, packaged quantum information processing becomes feasible and testable. Our results show that the gauge-invariant packaged quantum states may provide a possible route toward robust, fault-tolerant, and secure quantum technologies.

quant-ph

Packaged Quantum States in Field Theory: No Partial Factorization, Multi-Particle Packaging, and Hybrid Gauge-Invariant Entanglement

We demonstrate that quantum field excitations can generate packaged entangled states, in which all internal quantum numbers (IQNs) (e.g., electric charge, flavor, and color) are inseparably entangled and constrained to irreducible representation (irrep) blocks. This is a consequence of local gauge invariance and superselection rules. The confinement restricts the net gauge charge to a single superselection sector, thereby excluding cross-sector superpositions but allowing entanglement within one sector. We establish theorems that: \textbf{(1)} Explain how these packaged entangled states naturally arise from quantum field excitations, \textbf{(2)} Show how they remain gauge invariant or transform covariantly within a fixed net-charge sector, and \textbf{(3)} Illustrate how external degrees of freedom (DOFs) (e.g., spin or momentum) can combine with packaged internal charges to yield gauge-invariant entanglement. Finally, we show that spin or momentum measurements on these hybrid states induce a collapse of the internal entanglement.

quant-ph

Packaged Quantum States for Quantum Simulation of Lattice Gauge Theories

We develop a mathematical framework for the quantum simulation of lattice gauge theories using gauge-invariant packaged quantum states \cite{Ma2017,Ma2025}. In this formalism, every single excitation transforms as a complete \textbf{irreducible representation (irrep)} of the local gauge group, preventing any appearance of fractional or partial \textbf{internal quantum numbers (IQNs)}. Multi-particle excitations can form nontrivial packaged entangled states that are also gauge invariant, thereby forbidding partial or fractional IQNs. In other words, all IQNs of such packaged entangled states remain inseparably entangled. This ``packaging principle'' ensures that physical states remain confined to the correct gauge sector and excludes partial charges or colors, even when multiple excitations are entangled. We illustrate this approach for $\mathrm{U}(1)$, $\mathrm{SU}(2)$, and $\mathrm{SU}(3)$ lattice gauge theories, discussing explicit constructions, Trotterized Hamiltonian evolution, and gauge-invariant measurements on a quantum simulator. We also outline how packaged states can mitigate gauge-violating errors and serve as natural building blocks for gauge-invariant coding schemes, while noting that standard quantum error correction is still required against typical local noise that respects gauge symmetry.

quant-ph

Melting through Barrier-Crossing: The Role of Equilibrium Thermally Activated Particles

Melting is often understood in purely equilibrium terms, where crystalline order disappears once the free energy of the solid equals that of the liquid. Yet at the microscopic level, the initiating events for melting can often be traced to the formation of defects or local ``jumps'' over interatomic barriers. In this work, we offer a unified interpretation of melting by focusing on the equilibrium fraction of particles whose energy exceeds a characteristic barrier \(E_a\). We show that when this fraction surpasses a small but critical threshold \cite{Feder1958,Kraftmakher1998} (on the order of \(10^{-4}\)-\(10^{-3}\)), the crystal loses its rigidity, thus reconciling Born's mechanical-instability picture with the older Lindemann notion of large atomic displacements. We derive this threshold condition from standard Boltzmann (and Bose/Fermi) statistics, ensuring consistency with standard thermodynamics. Our approach naturally extends to vortex lattices in superconductors (where vortex activation energies play the role of \(E_a\)) and to quantum-lattice systems (Hubbard-type models). Crucially, while the interpretation emphasizes barrier crossing, the criterion itself is built on equilibrium statistical mechanics, offering a transparent link between defect formation rates and the macroscopic transition.

cond-mat.supr-con

Erasing and Correction of Liquid Metal Printed Electronics Made of Gallium Alloy Ink from the Substrate

Gallium-based liquid metals have recently been found important in a variety of newly emerging applications such as room temperature metal 3D printing, direct writing of electronics and biomedicine etc. In all these practices, one frequently encounters the situations that a printed circuit or track needs to be corrected or the unwanted parts of the device should be removed as desired. However, few appropriate strategies are currently available to tackle such important issues at this stage. Here we have identified several low cost ways toward this goal by comparatively investigating three typical strategies spanning from mechanical, chemical, to electrochemical principles, for removing the gallium-based liquid metal circuits or thin films. Regarding the mechanical approach, we constructed an eraser for removing the liquid metal thin films. It was shown that ethanol (CH3CH2OH) could serve as a good candidacy material for the mechanical eraser. In the chemical category, we adopted alkalis and acids to remove the finely printed liquid metal circuits and sodium hydroxide (NaOH) solution was particularly revealed to be rather efficient in making a chemical eraser. In the electrochemical strategy, we applied a 15 V voltage to a liquid metal thin film (covered with water) and successfully removed the target metal part. These methods were comparatively evaluated with each of the merits and shortcomings preliminarily clarified in the end. The present work is expected to be important for the increasing applications of the liquid metal enabled additive manufactures.

physics.app-ph

Theory of packaged entangled states

The entangled states that include every physical properties of particles would be important for both theoretical and applied physics. However, the existence and properties of such entangled states are unclear at present. Here we theoretically show that a particle-antiparticle pair can form the so-called packaged entangled states which encapsulate all the necessary physical quantities for completely identifying the particles. The particles in the packaged entangled states are indeterminate and exhibit unusual properties. Thereafter, we discussed the possible applications of these new entangled states, i.e., the protocol for teleporting the entire quantum state of a particle (or an antiparticle) to an arbitrarily large distance without a classical channel, transfer of the new entangled states from a particle pair to another particle pair, and new interpretation to the matter-antimatter asymmetry of the observable universe.

physics.gen-ph

Break-up phenomena of liquid metal thin film induced by high electric current

The room temperature liquid metal related electronics has been found important in a wide variety of emerging areas over the past few years. However, its failure features under high electrical current densities are not clear until now. Here we show that a liquid metal thin film would break-up as the applied current increases to a critical magnitude. The break-up phenomenon is attributed to be caused by the so-called electromigration effect. This problem could be one of the major hurdles that must be tackled with caution in the research and application of future liquid metal film electronics.

cond-mat.mtrl-sci

Flux exchange in inhomogeneous type-II superconductors

The vortex hopping motion in a type-II superconductor determines the current-carrying ability and consequently the application fields of the superconductor. However, it is not clear how the vortices hop between the different pinning regions in the superconductor. Here we proposed that there should be magnetic \textit{flux exchange} between two contacting pinning regions. A system of differential equations was constructed to describe the flux exchange phenomenon. The qualitative analysis methods were used. The approximate numerical solutions and approximate analytical solutions of the system were obtained. The results show that the flux exchange reduces the internal field in a weak pinning region, but increases the internal field in a strong pinning region. Moreover, the flux exchange phenomenon is strongly influenced by the superconductor's geometrical size.

cond-mat.supr-con

Determination of critical current density from arbitrary flux relaxation process

The current-carrying ability of a type-II superconductor is generally represented by its critical current density. This can be determined by measuring a flux relaxation process starting with a testing current density that is greater than or equal to the critical value. Here we show that a flux relaxation process starting with an intermediate current density can be converted into a process starting with the critical current density by introducing a virtual time interval. Therefore, one may calculate the critical current density from the flux relaxation process starting with a current density below the critical value. The exact solutions of the time dependence of current density in the flux relaxation process were also discussed.

cond-mat.supr-con

Infinite series models of flux relaxation and vortex penetration constructed at critical points and their unification

The information about the current-carrying ability of a type-II superconductor can be obtained by studying the flux relaxation and vortex penetration phenomena in the superconductor. In early studies, the infinite series models of the flux relaxation and vortex penetration phenomena were constructed at a vanishing current density and vanishing internal field, respectively. However, this is not the only possibility. Here it is shown that one can reconstruct the theoretical models at the critical points. The new polynomial model of the flux relaxation (vortex penetration) phenomenon was constructed by expanding the vortex activation energy as an infinite series of the current density (internal field) about the critical current density (equilibrium internal field). The unification of the polynomial models was proposed. The inverse model of the flux relaxation (vortex penetration) phenomenon was also constructed by expanding the vortex activation energy as an infinite series of the inverse current density (inverse internal field) about the critical current density (equilibrium internal field).

cond-mat.supr-con

Vortex penetration and flux relaxation with arbitrary initial conditions in non-ideal and ideal superconductors

Vortex penetration and flux relaxation phenomenon carry the information about the pinning ability, and consequently current-carrying ability, of a type-II superconductor. However, the theoretical descriptions to these phenomena are currently limited to the cases with special initial conditions. A generalization to the recently developed infinite series models is presented here. It is shown that one can convert a vortex penetration process with a non-zero initial internal field into a process with a zero initial internal field by introducing some time parameters. Similarly, one can also convert a flux relaxation process starting with an arbitrary internal field into a process starting with a melting internal field by introducing a virtual time interval. Therefore, one can predict the melting internal field (or critical current density) from a flux relaxation process starting with a lower internal field. Finally, it is shown that the vortex penetration process in an ideal superconductor is strongly time dependent because of the surface barrier and internal field repulsive force. But the flux relaxation process does not occur in the ideal superconductor.

cond-mat.supr-con

Mathematical model of vortex penetration phenomenon

Vortex penetration affects the stability of a superconducting system and limits the possible application of the system. However, the mathematical description to this phenomenon is currently unavailable. Here I present a mathematical model in which I consider the effects of bulk pinning and internal field repulsive force on vortex hopping. Thereafter, I proposed a series expansion to the activation energy and derived a general formula for describing the time dependence of the vortex penetration process. With these formulas, I can analyze the experimental data and calculate the activation energy of the vortex penetration phenomenon. The results are accurate for the time dependence of the internal field measurements in a $Bi_2Sr_2CaCu_2O_{8+x}$ superconductor.

cond-mat.supr-con

Mathematical model of flux relaxation phenomenon

The investigations on the flux relaxation phenomenon of a type-II superconductor are important because they provide the information about the flux pinning ability and current-carrying ability of the superconductor. However, a unified theory of flux relaxation is currently unavailable. Here I present a general mathematical model of the flux relaxation. In this model, I proposed a series expansion to the activation energy and derived a general formula for the current decay behavior. In the light of these formulas, I can analyze the experimental data on the current decay behavior and then calculate the activation energy of a vortex system without subjecting to any special conditions. The results are accurate for the current decay measurements from a $Bi_2Sr_2CaCu_2O_{8+x}$ superconductor

cond-mat.supr-con