arXiv subjects

Ori Grossman

Publications and source records attributed to Ori Grossman.

5 recordsLinked to original sources

arXiv2026

Trapped-Ion Multiqubit Gates are Compatible with Scalable Quantum Error Correction

We construct a detailed microscopic noise model for multi-qubit (MQ) gate operations in the context of trapped ion architecture with all-to-all connectivity. We find that phonon heating and motional dephasing are well captured by effective single- and two-qubit error channels that can, in principle, act between arbitrary pairs of qubits. Nevertheless, the median magnitude of two-qubit errors between uncoupled qubits is substantially smaller than that of errors between gate-coupled qubits. Errors associated with photon scattering are shown to solely propagate to qubits participating in gate operations. Lastly, we combine all noise sources, assigned with experimentally relevant parameters, and explore the scalability of a quantum error correction (QEC) scheme based on the rotated surface code, as a function of error rates and code size. Our analysis bridges device-level physics and QEC performance for MQ gates in trapped-ion architectures.

quant-ph↗

arXiv2025

Topological excitations at time vortices in periodically driven systems

We consider two-dimensional periodically driven systems of fermions with particle-hole symmetry. Such systems support non-trivial topological phases, including ones that cannot be realized in equilibrium. We show that a space-time defect in the driving Hamiltonian, dubbed a ``time vortex,'' can bind $π$ Majorana modes. A time vortex is a point in space around which the phase lag of the Hamiltonian changes by a multiple of $2π$. We demonstrate this behavior on a periodically driven version of Kitaev's honeycomb spin model, where $\mathbb{Z}_2$ fluxes and time vortices can realize any combination of $0$ and $π$ Majorana modes. We show that a time vortex can be created using Clifford gates, simplifying its realization in near-term quantum simulators.

cond-mat.str-el↗

arXiv2023

Robust Fermi liquid instabilities in sign problem-free models

Determinant Quantum Monte Carlo (DQMC) is a powerful numerical technique to study many-body fermionic systems. In recent years, several classes of sign-free (SF) models have been discovered, where the notorious sign problem can be circumvented. However, it is not clear what are the inherent physical characteristics and limitations of SF models. In particular, which zero-temperature quantum phases of matter are accessible within such models, and which are fundamentally inaccessible? Here, we show that a model belonging to any of the known SF classes within DQMC cannot have a stable Fermi liquid ground state in spatial dimension $d\ge 2$, unless the anti-unitary symmetry that prevents the sign problem is spontaneously broken (for which there are currently no known examples in SF models). For SF models belonging to one of the symmetry classes (where the absence of the sign problem follows from a combination of non-unitary symmetries of the fermionic action), any putative Fermi liquid fixed point generically includes an attractive Cooper-like interaction that destabilizes it. In the recently discovered lower-symmetry classes of SF models, the Fermi surface is generically unstable even at the level of the quadratic action. Our results suggest a fundamental link between Fermi liquids and the fermion sign problem. Interestingly, our results do not rule out a non-Fermi liquid ground state with a Fermi surface in a sign-free model.

cond-mat.str-el↗

arXiv2023

Weakly damped bosons and precursor gap in the vicinity of an antiferromagnetic metallic transition

We study the electronic spectral function of a metal in the vicinity of an antiferromagnetic (AFM) quantum critical point, focusing on a situation where the bare bandwidth of the spin fluctuations is significantly smaller than the Fermi energy. In this limit, we identify a range of energies where the fermionic quasiparticles near the "hot spots'' on the Fermi surface are strongly scattered by the quantum critical fluctuations, whereas the damping of the AFM fluctuations by the electrons is negligible. Within a one-loop approximation, there is a parameter range where the $T=0$ spectral function at the hot spots has a "precursor gap'' feature, with a local maximum at a finite frequency. However, the ratio of the bare spin wave velocity to the Fermi velocity required to obtain a precursor gap is probably too small to explain experiments in the electron-doped cuprate superconductors (He et al., Proc. Natl. Acad. Sci 116, 3449 (2019)). At lower frequencies, the Landau damping of the AFM fluctuations becomes important, and the electronic spectral function has the familiar $ω^{-1/2}$ singularity. Our one-loop perturbative results are supported by a numerical Monte Carlo simulation of electrons coupled to an undamped, nearly-critical AFM mode.

cond-mat.str-el↗

arXiv2021

Specific Heat of a Quantum Critical Metal

We investigate the specific heat, $c$, near an Ising nematic quantum critical point (QCP), using sign problem-free quantum Monte Carlo simulations. Cooling towards the QCP, we find a broad regime of temperature where $c/T$ is close to the value expected from the non-interacting band structure, even for a moderately large coupling strength. At lower temperature, we observe a rapid rise of $c/T$, followed by a drop to zero as the system becomes superconducting. The spin susceptibility begins to drop at roughly the same temperature where the enhancement of $c/T$ onsets, most likely due to the opening of a gap associated with superconducting fluctuations. These findings suggest that superconductivity and non-Fermi liquid behavior (manifested in an enhancement of the effective mass) onset at comparable energy scales. We support these conclusions with an analytical perturbative calculation.

cond-mat.str-el↗