arXiv subjects

Bhavik Kumar

Publications and source records attributed to Bhavik Kumar.

4 recordsLinked to original sources

arXiv2026

Solvable Quantum Circuits with non-Markovian Influence Matrices

Influence matrices encode the action exerted on local subsystems by the rest of an extended quantum many-body system during their evolution. Thus, knowledge of the influence matrix facilitates computationally efficient simulations of local dynamics. Here we propose a new systematic approach to generating quantum circuits with complex dynamics for which the influence matrices can be written down exactly. In contrast to previous frameworks of this kind, such as dual-unitary circuits, the resulting influence matrices are non-Markovian, exhibiting nontrivial temporal correlations. We explicitly construct a broad family of circuits of this kind, based on dressing free-fermion (matchgate) circuits with appropriately chosen interaction terms. We show that, contrary to previous solvable instances, these circuits produce patterns of correlations that closely resemble that of typical many-body systems. Our approach can be directly interpreted in terms of an error correction scheme where the terms breaking the solvability of the influence matrices play the role of errors.

cond-mat.stat-mech↗

arXiv2025

Estimating applied potentials in cold atom lattice simulators

Cold atoms in optical lattices are a versatile and highly controllable platform for quantum simulation, capable of realizing a broad family of Hubbard models, and allowing site-resolved readout via quantum gas microscopes. In principle, arbitrary site-dependent potentials can also be implemented; however, since lattice spacings are typically below the diffraction limit, precisely applying and calibrating these potentials remains challenging. Here, we propose a simple and efficient experimental protocol that can be used to measure any potential with high precision. The key ingredient in our protocol is the ability in some atomic species to turn off interactions using a Feshbach resonance, which makes the evolution easy to compute. Given this, we demonstrate that collecting snapshots from the time evolution of a known, easily prepared initial state is sufficient to accurately estimate the potential. Our protocol is robust to state preparation errors and uncertainty in the hopping rate. This paves the way toward precision quantum simulation with arbitrary potentials.

cond-mat.quant-gas↗

arXiv2024

Stabilizing Quantum Simulators Of Gauge Theories Against $1/f$ Noise

This work investigates the application of quantum simulation in the ongoing "second" quantum revolution, which employs various synthetic quantum matter platforms, such as ultracold atoms in optical lattices, Rydberg atoms, and superconducting qubits, to realize exotic condensed matter and particle physics phenomena with high precision and control. Gauge theories are of particular interest in modern quantum simulators as they offer a new probe of high-energy physics on low-energy tabletop devices. However, to accurately model gauge-theory phenomena on a quantum simulator, stabilizing the underlying gauge symmetry is crucial. Through this thesis we demonstrate that a recently developed experimentally feasible scheme based on linear gauge protection, initially devised to protect against coherent gauge breaking errors, can also be used to suppress incoherent errors arising from $1/f^{\beta}$ noise prominent in various quantum simulation platforms. The Bloch-Redfield formalism is introduced to model gauge violations arising due to these incoherent errors given the noise power spectrum of the environment. The efficacy of linear gauge protection in stabilizing salient features of gauge theories in quantum simulators, such as gauge invariance and exotic far from equilibrium phenomenon focusing on disorder-free localization, and quantum many-body scars against $1/f^{\beta}$ noise sources, is illustrated. These results are immediately applicable in modern analog quantum simulators and digital NISQ devices, paving the way for further development in the field of quantum simulation of lattice gauge theories.

quant-ph↗

arXiv2022

Suppression of $1/f$ noise in quantum simulators of gauge theories

In the current drive to quantum-simulate evermore complex gauge-theory phenomena, it is necessary to devise schemes allowing for the control and suppression of unavoidable gauge-breaking errors on different experimental platforms. Although there have been several successful approaches to tackle coherent errors, comparatively little has been done in the way of decoherence. By numerically solving the corresponding Bloch--Redfield equations, we show that the recently developed method of \textit{linear gauge protection} suppresses the growth of gauge violations due to $1/f^\beta$ noise as $1/V^\beta$, where $V$ is the protection strength and $\beta>0$, in Abelian lattice gauge theories, as we show through exemplary results for $\mathrm{U}(1)$ quantum link models and $\mathbb{Z}_2$ lattice gauge theories. We support our numerical findings with analytic derivations through time-dependent perturbation theory. Our findings are of immediate applicability in modern analog quantum simulators and digital NISQ devices.

quant-ph↗