Magnetic Gradiometer for Detection of Zero- and Ultralow-Field Nuclear Magnetic Resonance

Magnetic sensors are important for detecting nuclear magnetization signals in nuclear magnetic resonance (NMR). As a complementary analysis tool to conventional high-field NMR, zero- and ultralow-field (ZULF) NMR detects nuclear magnetization signals in the sub-microtesla regime. Current ZULF NMR systems are always equipped with high-quality magnetic shieldings to ensure that ambient magnetic field noise does not dwarf the magnetization signal. An alternative approach is to separate the magnetization signal from the noise based on their differing spatial profiles, as can be achieved using a magnetic gradiometer. Here, we present a gradiometric ZULF NMR spectrometer with a magnetic gradient …

Social Memory and the Resilience of Communities Affected by Land Degradation

Law, Borders, and Speech Conference: Proceedings and Materials

Tensions between national law and the Internet’s global architecture have existed since the network’s earliest days. They took on new urgency in recent years, with developments like French regulators’ efforts to globally enforce “Right to Be Forgotten” laws. New cases, technologies, and platform responses seem to come along every few months. Expert-level discussion of these issues is dynamic and fast-moving -- but the written literature is only starting to catch up. This volume contributes to that literature by capturing insights from the Stanford Center for Internet and Society’s Law, Borders, and Speech conference. The event honored the twentieth anniversary of David G. Post and David R. …

Nuclear-spin comagnetometer based on a liquid of identical molecules

Atomic comagnetometers are used in searches for anomalous spin-dependent interactions. Magnetic field gradients are one of the major sources of systematic errors in such experiments. Here we describe a comagnetometer based on the nuclear spins within an ensemble of identical molecules. The dependence of the measured spin-precession frequency ratio on the first-order magnetic field gradient is suppressed by over an order of magnitude compared to a comagnetometer based on overlapping ensembles of different molecules. Our single-species comagnetometer is shown to be capable of measuring the hypothetical spin-dependent gravitational energy of nuclei at the $10^{-17}$ eV level, comparable to the…

Experimental benchmarking of quantum control in zero-field nuclear magnetic resonance

Zero-field nuclear magnetic resonance (NMR) provides complementary analysis modalities to those of high-field NMR and allows for ultra-high-resolution spectroscopy and measurement of untruncated spin-spin interactions. Unlike for the high-field case, however, universal quantum control -- the ability to perform arbitrary unitary operations -- has not been experimentally demonstrated in zero-field NMR. This is because the Larmor frequency for all spins is identically zero at zero field, making it challenging to individually address different spin species. We realize a composite-pulse technique for arbitrary independent rotations of $^1$H and $^{13}$C spins in a two-spin system. Quantum-inform…

Search for axion-like dark matter with spin-based amplifiers

Ultralight axion-like particles (ALPs) are well-motivated dark matter candidates introduced by theories beyond the standard model. However, the constraints on the existence of ALPs through existing laboratory experiments are hindered by their current sensitivities, which are usually weaker than astrophysical limits. Here, we demonstrate a new quantum sensor to search for ALPs in the mass range that spans about two decades from 8.3 feV to 744 feV. Our sensor makes use of hyperpolarized long-lived nuclear spins as a pre-amplifier that effectively enhances coherently oscillating axion-like dark-matter field by a factor of >100. Using spin-based amplifiers, we achieve an ultrahigh magnetic s…

Search for exotic spin-dependent interactions with a spin-based amplifier

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