arXiv subjects

Erik Van Dyke

Publications and source records attributed to Erik Van Dyke.

4 recordsLinked to original sources

arXiv2026

Parahydrogen Cooling of Nuclear Spin Chains at Hypogeomagnetic Fields

Solution-state molecular nuclear spin networks are promising quantum simulators because their scalar-coupling Hamiltonians are chemically programmable, precisely measurable, and coherent at room temperature. Their main limitation for quantum information science is initialization: thermal Boltzmann polarization produces highly mixed, high-entropy states. Here, we use parahydrogen-based Signal Amplification by Reversible Exchange (SABRE) at hypogeomagnetic fields (i.e., magnetic fields below Earth field) to hyperpolarize the chemically engineered 12-spin chain [U-13C,15N]-butyronitrile. SABRE generates percent-level 13C and 15N polarization and prepares non-equilibrium multi-spin orders across the network. A von Neumann entropy analysis of such a hyperpolarized system shows that, at the optimal transfer field of 0.52 uT, the full spin system could reach S/k = 8.274, compared with S/k = 8.318 for the unpolarized reference, giving (S-Sth)/k = -0.043. Experimentally, nuclear spin temperatures of 52 mK and 257 mK are achieved for 15N and 13C subensembles, respectively. The larger entropy deficit of the full network than of individual subsystems indicates correlated multi-spin order beyond single-spin polarizations. Rapid field cycling to 9.4 T enables site-resolved NMR readout, while the precisely determined coupling network provides an experimentally benchmarked Hamiltonian for testing quantum-simulation, quantum-control, and Hamiltonian-learning protocols.

quant-ph↗

arXiv2026

High-Field NMR Characterization and Indirect $J$-Spectroscopy of a Nuclear Spin Chain [U-$^{13}$C,$^{15}$N]-butyronitrile

One-dimensional chains of coupled spins are minimal models of strongly correlated quantum matter, and have been proposed as wires for transporting quantum information. In liquids, rapid molecular tumbling averages anisotropic dipolar couplings and leaves effective isotropic scalar $J$-coupling Hamiltonians. At zero- to ultralow-field (ZULF) conditions, differences in frequency between nuclear spins of different types are quenched and the internal Hamiltonians can be closely approximated by an isotropic Heisenberg model. In this work, we present [U-$^{13}$C,$^{15}$N]-butyronitrile as a chemically engineered nuclear spin chain whose full spin-spin coupling network can be determined and validated by combining high-field NMR detection with evolution at ultralow fields. Starting from high-field (16.4 T) NMR spectra of $^1$H, $^{13}$C, and $^{15}$N nuclei, we extract all relevant $J$-couplings within a 12-spin network (four $^{13}$C, one $^{15}$N, and seven $^1$H). We then employ a mechanical field-cycling apparatus to prepolarize the spins at high field, shuttle them into a magnetically shielded region for evolution at <50 nT, and detect signals after returning to high field. Fourier analysis of the ultralow-field evolution yields indirect $J$-spectra that are conceptually analogous to ZULF NMR spectra but measured by a high-field NMR spectrometer. We observe clear spectral features at $J$, 1.5$J$, and 2$J$, in good agreement with simulations using the extracted coupling matrix. Finally, we demonstrate 2D experiments that correlate high-field chemical shifts and, thus, fully map interactions within the molecular spin chain. Our results establish [U-$^{13}$C,$^{15}$N]-butyronitrile as an extremely well-characterized spin chain model system and provide a quantitative Hamiltonian benchmark for future hyperpolarization and quantum-control studies.

quant-ph↗

arXiv2024

Towards detection of molecular parity violation via chiral co-sensing: the $^1$H/$^{31}$P model system

Fundamental weak interactions have been shown to violate parity in both nuclear and atomic systems. However, observation of parity violation in a molecular system has proven an elusive target. Nuclear spin dependent contributions of the weak interaction are expected to result in energetic differences between enantiomers manifesting in nuclear magnetic resonance (NMR) spectra as chemical shift differences on the order of $10^{-6}$ Hz to $10^{-3}$ Hz for high-$Z$ nuclei. By employing simultaneous measurements of the diastereomeric splittings for a light and a heavy nucleus in solution-state NMR, residual chemical shift differences persisting in non-chiral environment between enantiomers of chiral compounds smaller than the typical linewidth of high-field NMR may be resolved. Sources of error must be identified and minimized to verify that the observed effect is, in fact, due to parity violation and not systematic effects. This paper presents a detailed analysis of a system incorporating \textsuperscript{31}P and \textsuperscript{1}H NMR to elucidate the systematic effects and to guide experiments with higher-$Z$ nuclei where molecular parity violation may be resolved.

physics.chem-ph↗

arXiv2024

Zero-Field J-spectroscopy of Quadrupolar Nuclei

Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) is a powerful version of NMR that allows studying molecules and their transformations in the regime dominated by intrinsic spin-spin interactions. While spin dynamics at zero magnetic field can be probed indirectly - via shuttling a sample that underwent evolution at zero field to a high-field NMR spectrometer for detection - J-spectra can also be measured directly at zero field by using non-inductive sensors, for example, atomic magnetometers. To date, no zero-field J-spectra of molecules featuring the coupling to quadrupolar nuclei were reported. Here we show that zero-field J-spectra can be collected from molecules containing quadrupolar nuclei with I = 1 and demonstrate this for solutions containing various isotopologues of ammonium cations, namely, 14NH4+ and 15NDxH(4-x)+ (where x = 0, 1, 2, or 3). Lower ZULF NMR signals are observed for molecules containing larger numbers of deuterons compared to protons; this is attributed to less overall magnetization and not to the scalar relaxation of the second kind. Values for the 15N-1H and 14N-1H J-couplings of -73.416(3) Hz, 52.395(2) Hz, respectively, are extracted from the ZULF NMR spectra. Precision measurement of the J(15NH)/J(14NH) ratio resulted in the value within a range of 1.4009-1.4013; this is statistically different from {γ_{15N}}/{γ_{14N}}=1.4027 reported in the literature indicating the presence of the primary isotope effect. We analyze the energy structure for the studied molecular cations in detail and demonstrate that spectral line positions depend dramatically both on the sign of each J-coupling and on the magnetic pulse length.

physics.chem-ph↗