arXiv subjects

Eric D. Switzer

Publications and source records attributed to Eric D. Switzer.

6 recordsLinked to original sources

arXiv2026

Lindblad Multiproduct Formulas

We introduce Lindblad Multiproduct Formulas: a quantum error mitigation technique that uses two-dimensional tensor networks contracted with loop-corrected belief propagation. The quantities required to implement the error mitigation scheme that are evaluated with tensor networks can be less computationally expensive to calculate than the expectation values themselves, thus allowing for the possibility of applying our method to certain systems for which tensor network methods may struggle to calculate the observable quantities of interest. The workflow incorporates Clifford rescaling techniques and outputs an estimated error bar. We apply our method to a model of two-dimensional discrete time crystals studied previously and implement it on $65$ qubits arranged in a $3\!\times\!3$ heavy-hexagonal topology on the quantum computer ibm_basquecountry. We show that a GPU implementation of the classical part of our workflow achieves a speedup of up to $5.6\times$.

quant-ph↗

arXiv2025

Unraveling spin entanglement using quantum gates with scanning tunneling microscopy-driven electron spin resonance

Quantum entanglement is a fundamental resource for quantum information processing, and its controlled generation and detection remain key challenges in scalable quantum architectures. Here, we numerically demonstrate the deterministic generation of entangled spin states in a solid-state platform by implementing quantum gates via electron spin resonance combined with scanning tunneling microscopy (ESR-STM). Using two titanium atoms on a MgO/Ag(100) substrate as a model, we construct a two-qubit system whose dynamics are coherently manipulated through tailored microwave pulse sequences. We generate Bell states by implementing a Hadamard gate followed by a controlled-NOT gate, and evaluate its fidelity and concurrence using the quantum-master equation-based code TimeESR. Our results demonstrate that ESR-STM can create entangled states with significant fidelity. This study paves the way for the realization of atom-based quantum circuits and highlights ESR-STM as a powerful tool for probing and engineering entangled states on surfaces.

quant-ph↗

arXiv2025

Realization of Two-dimensional Discrete Time Crystals with Anisotropic Heisenberg Coupling

A discrete time crystal (DTC) is the paradigmatic example of a phase of matter that occurs exclusively in systems out of equilibrium. This phenomenon is characterized by the spontaneous symmetry breaking of discrete time-translation and provides a rich playground to study a fundamental question in statistical physics: what mechanism allows for driven quantum systems to exhibit emergent behavior that deviates from their counterparts with time-independent evolution? Unlike equilibrium phases, DTCs exhibit macroscopic manifestations of coherent quantum dynamics, challenging the conventional narrative that thermodynamic behavior universally erases quantum signatures. However, due to the difficulty of simulating these systems with either classical or quantum computers, previous studies have been limited to a set of models with Ising-like couplings -- and mostly only in one dimension -- thus precluding our understanding of the existence (or not) of DTCs in models with interactions that closely align with what occurs in nature. In this work, by combining the latest generation of IBM quantum processors with state-of-the-art tensor network methods, we are able to demonstrate the existence of a DTC in a two-dimensional system governed by anisotropic Heisenberg interactions. Our comprehensive analysis reveals a rich phase diagram encompassing spin-glass, ergodic, and time-crystalline phases, highlighting the tunability of these phases through multiple control parameters. Crucially, our results emphasize the interplay of initialization, interaction anisotropy, and driving protocols in stabilizing the DTC phase. By extending the study of Floquet matter beyond simplified models, we lay the groundwork for exploring how driven systems bridge the gap between quantum coherence and emergent non-equilibrium thermodynamics.

quant-ph↗

arXiv2023

Mapping Spin Interactions from Conductance Peak Splitting in Coulomb Blockade

We investigate the transport properties of a quantum dot coupled to leads interacting with a multi-spin system using the generalized master equation within the Coulomb blockade regime. We find that if two states for each scattering region electron manifold are included, several signatures of the interacting spin system appear in steady-state transport properties. We provide a theoretical mapping of differential conductance peak signatures and all spin Hamiltonian parameters related to the inclusion of excited state transitions between uncharged and charged electron manifolds. Our predictions describe a scheme of only using a quantum dot and differential conductance to measure magnetic anisotropy, inter-spin exchange coupling, exchange coupling between the spin system and itinerant electron, and applied magnetic field response.

cond-mat.mes-hall↗

arXiv2022

Electronic control and switching of entangled spin state using anisotropy and exchange in the three-particle paradigm

We explore the control and switching of the entangled spin states of multi-spin particle qubit coupled to an electron using a three-particle spin model described by $S_i$ ($i=1,2,3$), in which $S_1=\tfrac{1}{2}$ is an electron and $S_{2,3}$ can have any spin with both exchange coupling and magnetic anisotropy. We derive a general formula for the existence of a switching (DJ) resonance for any spin $S_{2,3}$. We further contrast the entanglement switching mechanisms for the $S_{2,3}=\tfrac{1}{2}$ and $S_{2,3}=1$ spin models. We find that while the onsite magnetic anisotropy in the case of $S_{2,3}>\tfrac{1}{2}$ allows full control of their spin states via interaction with $S_1$, in order to achieve acceptable control of a Bloch vector within the $S_{2,3}=\tfrac{1}{2}$ model, additional mechanisms, such as anisotropic exchange coupling, are required.

quant-ph↗

arXiv2021

Anisotropy-Exchange Resonance as a Mechanism for Entangled State Switching

We explore the three-particle spin model of an $S_{1}=\frac{1}{2}$ particle (e.g. a stationary electron) interacting with two spin-coupled $S_{\text{2,3}}$ particles with exchange coupling and magnetic anisotropy. We find that in the case of $S_{2,3}=1$ particles, the coupled particle entanglement states can be prepared, controlled, and read by the $S_{1}$ particle. We also find that for particular resonance conditions of the magnetic anisotropy strength $D$ and exchange coupling strength $J$, the entanglement state switching behavior is maximized and is robust against a range of anisotropic application of the exchange coupling.

quant-ph↗