arXiv subjects

Matthias Diez

Publications and source records attributed to Matthias Diez.

10 recordsLinked to original sources

arXiv2026

All-optical universal control of nuclear-spin qudits in trapped neutral atoms

Quantum systems with more than two levels - so-called qudits - offer increased computational density and reduced circuit complexity compared to qubit-based architectures, but achieving universal and scalable control remains challenging. We propose an all-optical scheme for universal qudit control in trapped neutral atoms in moderate to high magnetic fields, focusing on the fermionic isotope 173Yb (I = 5/2). The strong hyperfine interaction in the 3P1 manifold enables fast and selective Raman transitions between nuclear-spin states in the 1S0 ground-state manifold using a single linearly polarized laser. For each neighboring transition in the qudit manifold, we identify a magic polarization angle that enables coherent, state-selective control while suppressing off-resonant excitations, with operation frequencies exceeding 100 kHz. Combined with phase-shift operations, this provides universal control of the full single-qudit space. We further discuss compatible two-qudit gates based on the Rydberg blockade mechanism, completing a universal gate set, and analyze state-selective readout schemes compatible with the proposed protocol. Our results identify 173Yb as a promising platform for high-fidelity, all-optical qudit-based quantum information processing.

quant-ph↗

arXiv2026

Magnetic coupling between nuclear motion and nuclear spins in molecules

Among the possible types of magnetic dipole interactions in molecular systems, couplings between nuclear motion and the nuclear spin have probably received the least attention in molecular spectroscopy. Although very small in comparison to effects related to electron spin, this type of hyperfine interaction plays an important role in the NMR spectroscopy of molecular systems. While measurement and prediction of spin-rotation tensors are a common place, vibrationally induced effects still lack a comprehensive description. In this article we develop a generic, theoretical framework that is well embedded in modern electronic structure theory and inspired by the Breit-Pauli Hamiltonian for electronic interactions, distinguishing between nuclear spin-orbit and spin-other-orbit contributions. We show that the interaction of nuclear spins with pseudorotational excitations of highly symmetric molecules may lead to experimentally accessible hyperfine splittings in NMR spectra, triggered by infrared light.

physics.chem-ph↗

arXiv2025

Kapitza's Pendulum as a Classical Prelude to Floquet-Magnus Theory

We present a pedagogical introduction to Floquet-Magnus theory through the classical example of Kapitza's pendulum - a simple system exhibiting nontrivial dynamical stabilization under rapid periodic driving. By deriving the equations of motion and analyzing the system using Floquet theory and the Magnus expansion, we obtain analytical stability conditions and effective evolution equations. While grounded in classical mechanics, the techniques are directly applicable to periodically driven quantum systems as well. The approach is fully analytical, using only tools from theoretical mechanics, linear algebra, and ordinary differential equations, and is suitable for instruction at the advanced undergraduate or graduate level.

physics.class-ph↗

arXiv2025

Single Qudit Control in $^{87}$Sr via Optical Nuclear Electric Resonance

Optical nuclear electric resonance (ONER) was recently proposed as a fast and robust single-qubit gate mechanism in $^{87}$Sr. Here, we demonstrate through numerical simulations that ONER can be extended to single-qudit control, addressing multiple one-level hyperfine transitions within the ten-dimensional nuclear-spin manifold. We identify suitable operating regimes and show that ONER enables high-fidelity spin manipulations, with simulated $\pi$-gate fidelities exceeding 99.9\%, while maintaining coherence under realistic parameter fluctuations. These results establish a proof-of-principle for optical qudit control in $^{87}$Sr and delineate practical parameter ranges for future experiments, highlighting ONER as a promising pathway toward high-dimensional quantum information processing.

quant-ph↗

arXiv2025

Molecular Pseudorotation in Phthalocyanines as a Tool for Magnetic Field Control at the Nanoscale

Metal phthalocyanines, a highly versatile class of aromatic, planar, macrocyclic molecules with a chelated central metal ion, are topical objects of ongoing research and particularly interesting due to their magnetic properties. However, while current focus lies almost exclusively on spin-Zeeman-related effects, the high symmetry of the molecule and its circular shape suggests the exploitation of light-induced excitation of twofold degenerate vibrational states in order to generate, switch and manipulate magnetic fields at the nanoscale. The underlying mechanism is a molecular pseudorotation that can be triggered by infrared pulses and gives rise to a quantized, small but controllable magnetic dipole moment. We investigate the optical stimulation of vibrationally-induced molecular magnetism and estimate changes in the magnetic shielding constants for confirmation by future experiments.

physics.chem-ph↗

arXiv2025

Optical Nuclear Electric Resonance in LiNa: Selective Addressing of Nuclear Spins Through Pulsed Lasers

Optical nuclear electric resonance (ONER), a recently proposed protocol for nuclear spin manipulation in atomic systems via short laser pulses with MHz repetition rate, exploits the coupling between the nuclear quadrupole moment of a suitable atom and the periodic modulations of the electric field gradient generated by an optically stimulated electronic excitation. In this theory paper, we extend the scope of ONER from atomic to molecular systems and show that molecular vibrations do not interfere with our protocol. Exploring the diatomic molecule LiNa as a first benchmark system, our investigation showcases the robustness with respect to molecular vibration, and the ability to address and manipulate each of the two nuclear spins independently, simply by adjusting the repetition rate of a pulsed laser. Our findings suggest that it might be possible to shift complicated spin manipulation tasks required for quantum computing into the time domain by pulse-duration encoded laser signals.

quant-ph↗

arXiv2025

Optical nuclear electric resonance as single qubit gate for trapped neutral atoms

The precise control of nuclear spin states is crucial for a wide range of quantum technology applications. Here, we propose a fast and robust single-qubit gate in $^{87}$Sr, utilizing the concept of optical nuclear electric resonance (ONER). ONER exploits the interaction between the quadrupole moment of a nucleus and the electric field gradient generated by its electronic environment, enabling spin level transitions via amplitude-modulated laser light. We investigate the hyperfine structure of the 5s$^2$~$^1S_{0}\rightarrow{}$~5s5p~$^3P_1$ optical transition in neutral $^{87}$Sr, and identify the magnetic field strengths and laser parameters necessary to drive spin transitions between the $m_I$ = -9/2 and $m_I$ = -5/2 hyperfine levels in the ground state. Our simulations show that ONER could enable faster spin operations compared to the state-of-the-art oscillations in this 'atomic qubit'. Moreover, we show that spin-flip operations exceeding 99.9\% fidelity can be performed even in the presence of typical noise sources. These results pave the way for significant advances in nuclear spin control, opening new possibilities for quantum memories and other quantum technologies.

quant-ph↗

arXiv2022

Identifying Time Scales in Particle Production from Fields

Particle production through ultra-strong electric fields is a well-studied research field. Nevertheless, despite repeated attempts to relate the production rate within the field to the formation time of a particle, the latter is still shrouded in mystery. We provide an interpretation of a particle distribution at finite times enabling us to isolate and, therefore, identify the relevant time scales regarding particle formation in quantum physics within and beyond perturbation theory.

hep-ph↗

arXiv2021

Sub-nanoscale Temperature, Magnetic Field and Pressure sensing with Spin Centers in 2D hexagonal Boron Nitride

Spin defects in solid-state materials are strong candidate systems for quantum information technology and sensing applications. Here we explore in details the recently discovered negatively charged boron vacancies ($V_B^-$) in hexagonal boron nitride (hBN) and demonstrate their use as atomic scale sensors for temperature, magnetic fields and externally applied pressure. These applications are possible due to the high-spin triplet ground state and bright spin-dependent photoluminescence (PL) of the $V_B^-$. Specifically, we find that the frequency shift in optically detected magnetic resonance (ODMR) measurements is not only sensitive to static magnetic fields, but also to temperature and pressure changes which we relate to crystal lattice parameters. Our work is important for the future use of spin-rich hBN layers as intrinsic sensors in heterostructures of functionalized 2D materials.

cond-mat.mtrl-sci↗

arXiv2020

Room Temperature Coherent Control of Spin Defects in hexagonal Boron Nitride

Optically active defects in solids with accessible spin states are promising candidates for solid state quantum information and sensing applications. To employ these defects as quantum building blocks, coherent manipulation of their spin state is required. Here we realize coherent control of ensembles of boron vacancy (V$_B^-$) centers in hexagonal boron nitride (hBN). Specifically, by applying pulsed spin resonance protocols, we measure spin-lattice relaxation time ($T_1$) of 18 $μ$s and spin coherence time ($T_2$) of 2 $μ$s at room temperature. The spin-lattice relaxation time increases by three orders of magnitude at cryogenic temperature. Furthermore, employing a two- and three-pulse electron spin-echo envelope modulation (ESEEM) we separate the quadrupole and hyperfine interactions with the surrounding nuclei. Finally, by applying a method to decouple the spin state from its inhomogeneous nuclear environment - a "hole-burning" - the spectral optically detected magnetic resonance linewidth is significantly reduced to several tens of kHz, thus extending the spin coherence time by a factor of three. Our results are important for employment of van der Waals materials for quantum technologies, specifically in the context of using hBN as a high-resolution quantum sensor for hybrid quantum systems including 2D heterostructures, nanoscale devices and emerging atomically thin magnets.

cond-mat.mes-hall↗