Imaging the Meissner effect in hydride superconductors using quantum sensors

By directly altering microscopic interactions, pressure provides a powerful tuning knob for the exploration of condensed phases and geophysical phenomena1. The megabar regime represents an interesting frontier, in which recent discoveries include high-temperature superconductors, as well as structural and valence phase transitions2-6. However, at such high pressures, many conventional measurement techniques fail. Here we demonstrate the ability to perform local magnetometry inside a diamond anvil cell with sub-micron spatial resolution at megabar pressures. Our approach uses a shallow layer of nitrogen-vacancy colour centres implanted directly within the anvil7-9; crucially, we choose a crystal cut compatible with the intrinsic symmetries of the nitrogen-vacancy centre to enable functionality at megabar pressures. We apply our technique to characterize a recently discovered hydride superconductor, CeH9 (ref. 10). By performing simultaneous magnetometry and electrical transport measurements, we observe the dual signatures of superconductivity: diamagnetism characteristic of the Meissner effect and a sharp drop of the resistance to near zero. By locally mapping both the diamagnetic response and flux trapping, we directly image the geometry of superconducting regions, showing marked inhomogeneities at the micron scale. Our work brings quantum sensing to the megabar frontier and enables the closed-loop optimization of superhydride materials synthesis.

Probing many-body dynamics in a two-dimensional dipolar spin ensemble

The most direct approach for characterizing the quantum dynamics of a strongly interacting system is to measure the time evolution of its full many-body state. Despite the conceptual simplicity of this approach, it quickly becomes intractable as the system size grows. An alternate approach is to think of the many-body dynamics as generating noise, which can be measured by the decoherence of a probe qubit. Here we investigate what the decoherence dynamics of such a probe tells us about the many-body system. In particular, we utilize optically addressable probe spins to experimentally characterize both static and dynamical properties of strongly interacting magnetic dipoles. Our experimental platform consists of two types of spin defects in nitrogen delta-doped diamond: nitrogen-vacancy colour centres, which we use as probe spins, and a many-body ensemble of substitutional nitrogen impurities. We demonstrate that the many-body system's dimensionality, dynamics and disorder are naturally encoded in the probe spins' decoherence profile. Furthermore, we obtain direct control over the spectral properties of the many-body system, with potential applications in quantum sensing and simulation.

Imaging stress and magnetism at high pressures using a nanoscale quantum sensor

Pressure alters the physical, chemical, and electronic properties of matter. The diamond anvil cell enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena. Here, we introduce and use a nanoscale sensing platform that integrates nitrogen-vacancy (NV) color centers directly into the culet of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging of both stress fields and magnetism as a function of pressure and temperature. We quantify all normal and shear stress components and demonstrate vector magnetic field imaging, enabling measurement of the pressure-driven α↔ϵ phase transition in iron and the complex pressure-temperature phase diagram of gadolinium. A complementary NV-sensing modality using noise spectroscopy enables the characterization of phase transitions even in the absence of static magnetic signatures.

Imaging the Local Charge Environment of Nitrogen-Vacancy Centers in Diamond

Characterizing the local internal environment surrounding solid-state spin defects is crucial to harnessing them as nanoscale sensors of external fields. This is especially germane to the case of defect ensembles which can exhibit a complex interplay between interactions, internal fields, and lattice strain. Working with the nitrogen-vacancy (NV) center in diamond, we demonstrate that local electric fields dominate the magnetic resonance behavior of NV ensembles at a low magnetic field. We introduce a simple microscopic model that quantitatively captures the observed spectra for samples with NV concentrations spanning more than two orders of magnitude. Motivated by this understanding, we propose and implement a novel method for the nanoscale localization of individual charges within the diamond lattice; our approach relies upon the fact that the charge induces a NV dark state which depends on the electric field orientation.

Bragg grating fabrication in germanosilicate fibers by use of near-UV light: a new pathway for refractive-index changes

Using 334-nm light, we demonstrate side writing of Bragg gratings with an index change of ~10(-4) in germanium-doped fibers. No hydrogen loading of the fibers was required. These gratings have the same temperature stability as gratings fabricated with 240-nm light. Our results suggest that photoionization is not needed for formation of gratings in Ge-doped glass. We observe an enhancement of the 334-nm photosensitivity in boron-codoped fibers and suggest that B facilitates a structural transformation of the glass.

A comparison of apparent mRNA half-life using kinetic labeling techniques vs decay following administration of transcriptional inhibitors

Several different techniques were used to determine the apparent half-lives of immunoglobulin gamma 2b heavy chain and kappa light chain mRNA's in mouse myeloma 4T001 and a mutant derived from 4T001, i.e., mutant I17. The mutant I17 Ig heavy chain mRNA lacks CH1 and has fused CH2 and CH3 domains resulting in a truncated protein. By all four techniques the Ig heavy chain mRNA from mutant I17 displays a half-life that is approximately 70% the half-life of Ig mRNA in 4T001 cells. However, the absolute values of apparent half-life varied by greater than twofold for both lines among several of the techniques employed. The half-life of Ig gamma 2b mRNA in 4T001 cells was found to be 6.4 h by measuring decay following administration of the adenosine analog DRB to block new mRNA synthesis and 5.7 hr by measuring accumulation in an approach to steady-state labeling protocol. In contrast, the observed Ig mRNA half-lives determined by measuring decay following administration of actinomycin D to block new mRNA synthesis, or in a pulse-chase analysis were 2.9 and 3.8 h, respectively. The apparent half-life for Ig kappa light chain mRNA was the same in the 4T001 and I17 lines using any one technique but the value varied depending on the technique from a high value of 5.9 h following DRB to a low value of 2.4 h with actinomycin decay. Approach to steady-state is theoretically the most accurate method to measure mRNA half-life when that value is less than the doubling time of the cells. Pulse-chase analyses are accurate for measuring mRNA half-life when that value is longer than the effective chase period. Measuring preformed message decay following administration of drugs to block new mRNA synthesis is adaptable over a range of half-lives, but the cells must be shown to retain correct RNA metabolism over the time frame of the experiment. Determining a correct half-life for a particular mRNA may not be feasible using only one method and may, in fact, require several different approaches until a consensus value emerges.

A molecular and structural analysis of the VH and VK regions of monoclonal antibodies bearing the A48 regulatory idiotype

The results presented in this paper explore the molecular basis for expression of the A48 regulatory Id (RI). A48 RI+ mAb derived from idiotypically manipulated mice molecularly resembled the A48 and UPC 10 prototypes of this system by utilizing a VHX24-Vk10 combination. Id expression by these antibodies was not restricted by a particular D region sequence, JH, or JK segment, but quantitative differences in Id expression were associated with utilization of different members of the VK10 germ-line gene families. The VL sequences of these A48 RI+ mAb has identified amino acid residues lying in four different idiotope-determining regions which may contribute to the structural correlate of this Id. A comparative sequence analysis of the VH regions of these VHX24 utilizing A48 RI+ mAb with several A48 RI+ mAb utilizing VHJ558 or VH7183 VH genes as well as a hybrid transfectoma antibody derived from two A48 RI-, VHJ558 utilizing hybridomas, all suggested that four nonconsecutive positions which lie outside the idiotope-determining regions may contribute structural elements toward expression of this Id. The VH and VL regions of the A48RI+, VHX24-Vk 10+ mAb showed low to moderate levels of somatic mutation which showed different patterns of distribution between the complementary determining region (CDR) and framework regions in the H and L chains. Although the VK sequences contained 50% of the replacement mutations in the CDR, with a replacement/silent mutation ratio of 10, the CDR of the VH sequences contained only 31% of the replacement mutations with a replacement/silent mutation ratio of 0.69.

A molecular and structural analysis of the VH and VK regions of monoclonal antibodies bearing the A48 regulatory idiotype

The results presented in this paper explore the molecular basis for expression of the A48 regulatory Id (RI). A48 RI+ mAb derived from idiotypically manipulated mice molecularly resembled the A48 and UPC 10 prototypes of this system by utilizing a VHX24-Vk10 combination. Id expression by these antibodies was not restricted by a particular D region sequence, JH, or JK segment, but quantitative differences in Id expression were associated with utilization of different members of the VK10 germ-line gene families. The VL sequences of these A48 RI+ mAb has identified amino acid residues lying in four different idiotope-determining regions which may contribute to the structural correlate of this Id. A comparative sequence analysis of the VH regions of these VHX24 utilizing A48 RI+ mAb with several A48 RI+ mAb utilizing VHJ558 or VH7183 VH genes as well as a hybrid transfectoma antibody derived from two A48 RI-, VHJ558 utilizing hybridomas, all suggested that four nonconsecutive positions which lie outside the idiotope-determining regions may contribute structural elements toward expression of this Id. The VH and VL regions of the A48RI+, VHX24-Vk 10+ mAb showed low to moderate levels of somatic mutation which showed different patterns of distribution between the complementary determining region (CDR) and framework regions in the H and L chains. Although the VK sequences contained 50% of the replacement mutations in the CDR, with a replacement/silent mutation ratio of 10, the CDR of the VH sequences contained only 31% of the replacement mutations with a replacement/silent mutation ratio of 0.69.

An immunoglobulin heavy chain gene deletion at direct repeats: nucleotide sequence and effect on mRNA accumulation

The DNA from the mouse myeloma cell, I17, which produces aberrant gamma 2b heavy chain mRNAs, was cloned and sequenced. The I17 mutant, and its parent line 10.1, share a small deletion at the splice junction of the CH1 domain which results in the absence of CH1 sequences from the mRNA. In addition, the genomic DNA of I17 has a deletion of 253 nucleotides which fuses the CH2 and CH3 exons, causes a frameshift of the next 43 amino acids and results in a truncated protein. The deleted nucleotides are flanked by two direct repeats of the CAGCA pentamer in the normal gene. One copy of the repeat and the interposed DNA is removed in the mutant. The DNA deletion is colinear with the mRNA. Both I17 and 10.1 cells have decreased accumulation of the secretory-specific gamma 2b mRNA. The amounts of membrane-specific gamma 2b mRNA are also affected in the mutants.