arXiv subjects

Dor Gabay

Publications and source records attributed to Dor Gabay.

8 recordsLinked to original sources

arXiv2025

Quantum-Classical Auxiliary Field Quantum Monte Carlo with Matchgate Shadows on Trapped Ion Quantum Computers

We demonstrate an end-to-end workflow to model chemical reaction barriers with the quantum-classical auxiliary field quantum Monte Carlo (QC-AFQMC) algorithm with quantum tomography using matchgate shadows. The workflow operates within an accelerated quantum supercomputing environment with the IonQ Forte quantum computer and NVIDIA GPUs on Amazon Web Services. We present several algorithmic innovations and an efficient GPU-accelerated execution, which achieves a several orders of magnitude speedup over the state-of-the-art implementation of QC-AFQMC. We apply the algorithm to simulate the oxidative addition step of the nickel-catalyzed Suzuki-Miyaura reaction using 24 qubits of IonQ Forte with 16 qubits used to represent the trial state, plus 8 additional ancilla qubits for error mitigation, resulting in the largest QC-AFQMC with matchgate shadow experiments ever performed on quantum hardware. We achieve a $9\times$ speedup in collecting matchgate circuit measurements, and our distributed-parallel post-processing implementation attains a $656\times$ time-to-solution improvement over the prior state-of-the-art. Chemical reaction barriers for the model reaction evaluated with active-space QC-AFQMC are within the uncertainty interval of $\pm4$ kcal/mol from the reference CCSD(T) result when matchgates are sampled on the ideal simulator and within 10 kcal/mol from reference when measured on QPU. This work marks a step towards practical quantum chemistry simulations on quantum devices while identifying several opportunities for further development.

quant-ph↗

arXiv2021

Multi-impurity chiral Kondo model: correlation functions and anyon fusion rules

The multichannel Kondo model supports effective anyons on the partially screened impurity, as suggested by its fractional impurity entropy. It was recently demonstrated for the multi-impurity chiral Kondo model, that scattering of an electron through the impurities depends on the anyon's total fusion channel. Here we study the correlation between impurity-spins. We argue, based on a combination of conformal field theory, a perturbative limit with a large number of channels $k$, and the exactly solvable two-channel case, that the inter-impurity spin correlation probes the anyon fusion of the pair of correlated impurities. This may allow, using measurement-only topological quantum computing protocols, to braid the multichannel Kondo anyons via consecutive measurements.

cond-mat.str-el↗

arXiv2020

A Generalized Uncertainty Principle from a Mediating Field

A generalized uncertainty principle is obtained from a conformally transformed action containing a scalar field and a unique constraint. The constraint's Lagrange multiplier is found to obey a relativistic diffusion equation transforming the internal coordinates of the scalar field, via the shift theorem. For an approximately conserved Noether current, the coupled wave- and diffusion-like equations are merged into an infinite-order partial differential equation (PDE). It is conjectured that infrared and ultraviolet divergences are naturally removed in studying the infinite-order PDE's corresponding propagator. It is further suggested that higher-order contributions of the associated commutation relations are reminiscent of a self-interaction not present in the current quantum theory.

hep-th↗

arXiv2020

On the Mediating Field in a Conformally Transformed Einstein Equation

A unique constraint is defined within the framework of scalar-tensor theories, whereby the conformal factor is fixed to the fluctuation associated to the effective mass of the Hamilton-Jacobi equation for a Klein-Gordon field. The effective mass is extended to its exponential form to remove any ghost (energy) states. The constraint's Lagrange multiplier $λ$, referred to as the mediating field, is shown to act as a mediator between the scalar and tensor degrees of freedom. In its linear form, Heisenberg's uncertainty principle appears as a natural artifact of the mediating field. In its exponential form, the mediating field is shown to be bound, nonsingular, and of increasing significance for smaller masses. Furthermore, in acquiring the stress-energy tensors, the cosmological constant $Λ$ is formulated for a stationary solution of the particle density and mediating field. As a result, the mysterious variation in $Λ$ is properly evaluated from its cosmological value to that of an electron, from which a 77 order difference is obtained. In our final remarks, the mediating field $λ$ is suggested to be characteristic of the vacuum's energy density.

gr-qc↗

arXiv2020

A Proposal for a Covariant Entropy Relation

A density-dependent conformal killing vector (CKV) field is attained from a conformally transformed action composed of a unique constraint and a Klein-Gordon field. The CKV is re-expressed into an information identity and studied in its integro-differential form for both null and time-like geodesics. It is conjectured that the identity corresponds to a generalized second law of thermodynamics which holographically relates the covariant entropy contained within a volumetric $n$- and $(n-1)$-form, starting from an $(n-2)$-spatial area. The time-like geodesics inherit an effective `geometric spin' while the null geodesics are suggested to obey the generalized covariant entropy bound so long as they conform to Einstein's equation of state. To then comply with the equation of state, a metriplectic system is introduced, whereby a newly defined energy functional is derived for the entropy. Such an entropy functional mediates the Casimir invariants of the Hamiltonian and therefore preserves the symplectic form of quantum mechanics. For null geodesics, the Poisson bracket of the entropy functional with the Hamiltonian is shown to elegantly result in Einstein's energy-mass relation.

hep-th↗

arXiv2019

A Lorenz gauge formulation for TDDFT

We describe the inclusion of electrodynamic fields in Time-Dependent Density Functional Theory (TDDFT) by incorporating both the induced scalar and vector potentials within the time-dependent Kohn-Sham equation. The Hamiltonian is described in both the Coulomb and Lorenz gauges, and the advantages of the latter are outlined. Integral expressions are defined for the retarded potentials of each gauge and a methodological approach to evaluate these nontrivial expressions with low computational cost is adopted. Various molecular structures of relatively small sizes are studied, including water, benzene, and conductive carbon chains. Absorption cross sections resulting from both pulse and boost excitations suggest a preserved gauge-invariance of the proposed formal approach to TDDFT in the weak magnetic field limit.

physics.chem-ph↗

arXiv2018

On a Modified Klein-Gordon Equation with Vacuum-Energy Contributions

We define a modified covariant Klein-Gordon (KG) equation containing quantum vacuum contributions arising from the self-interaction of matter with its own internal kinetic energy. The modified KG equation is exemplified for a variety of vacuum fields and various properties of the equation are articulated thereof. Generalized commutation and Energy-Momentum relations are characterized for a null vacuum-phase scenario of the proposed vacuum field $λ$. Within this limited scenario, a representation theorem is introduced suggesting that one can equally modify the spacetime structure or momentum operator in articulating the proposed quantum theory. Such a modified KG equation is further shown to eliminate infrared and the ultraviolet divergences in the generalized Klein-Gordon propagator.

gr-qc↗

arXiv2017

Size dependent electronic properties of silicon quantum dots - an analysis with hybrid, screened hybrid and local density functional theory

We use an efficient projection scheme for the Fock operator to analyze the size dependence of silicon quantum dots (QDs) electronic properties. We compare the behavior of hybrid, screened hybrid and local density functionals as a function of the dot size up to $\sim$800 silicon atoms and volume of up to $\sim$20nm$^3$. This allows comparing the calculations of hybrid and screened hybrid functionals to experimental results over a wide range of QD sizes. We demonstrate the size dependent behavior of the band gap, density of states, ionization potential and HOMO level shift after ionization. Those results are compared to experiment and to other theoretical approaches, such as tight-binding, empirical pseudopotentials, TDDFT and GW.

physics.chem-ph↗