Understanding how matter complexifies, ultimately towards life, is a longstanding challenge embraced by the Matter-to-Life program. Since life as we know it is primarily chemistry, the challenge amounts to understanding how complexity and function can emerge and grow in a complicated chemical network. This grant supports Leroy Cronin, Professor of Chemistry at the University of Glasgow, to deploy a systems chemistry approach to addressing this question. Cronin will leverage state-of-the-art robotics to enable long-term chemical evolution experiments that exploit a new parameter that quantifies molecular complexity that is both experimentally accessible and embedded within a larger theoretical framework. Cronin plans to use that framework to nudge a chemical system towards ever-increasing complexity. Selection as a concept is most commonly deployed within Darwinian evolution, where natural selection refers to the preferential survival of individuals with certain genetic traits by means of natural controlling factors. Here Professor Cronin proposes to observe selection within a chemical system, and in this context, selection refers to the preferential survival of molecules with certain traits by means of natural controlling factors (the local environment). Cronin is primarily interested in one trait: complexity. Professor Cronin will use a measure of molecular complexity called the “assembly index.” The assembly index of a molecule is, in essence, equal to the number of ‘steps’ (chemical bonds) needed to construct the molecule using system-dependent basic building blocks (atoms or molecules).  Cronin has demonstrated that assembly index is well-correlated to three relatively-easy-to-perform types of measurements: mass spectrometry, IR spectroscopy, and NMR spectroscopy. The research team will run recursive chemistry experiments that rely on automated measurements to determine which molecules are present and adjust conditions to nudge a system towards a ‘selection regime’ where new forms of complexity are generated. The adjustable conditions include things like temperature (heating & cooling), evaporation and rehydration, how long a mixture is stirred, the duration of an experimental cycle, solution pH, whether various minerals are added, and whether or not an electrical discharge is applied. Cronin expects that a single experiment (a series of cycles) will run continuously for several hundred cycles, corresponding to several weeks or months. Over that time, there are four types of complex molecules / structures that the researchers will seek to detect: self-reproducing molecules and autocatalytic sets; production of high assembly index molecules; formation of primitive sequence polymers; and emergence of microscopic containers.

Training the next generation of researchers is an essential component of any healthy academic field. Here William Bialek and Joshua Shaevitz, Professors of Physics at Princeton University and Co-Directors of the Center for the Physics of Biological Function, request three years of support for a Center Fellow pursuing physics-of-life research. This prestigious postdoctoral fellowship will offer a young researcher both intellectual freedom and a support structure, and grant funds would support either a theorist or an experimentalist. A fellowship offering intellectual freedom to an early-career scholar is typically challenging to fund through federal agencies focused on supporting specific projects, despite the fact that this freedom can play an important role in establishing a young scientist as an independent researcher. The Center for the Physics of Biological Function is a partnership between Princeton and the Graduate Center of the City University of New York; a partnership anchored by a core community of sixteen CUNY/Princeton faculty. The Center focuses on science at the interface of physics and biology with the goal of creating ‘a physicist’s understanding of living systems: a physics of biological function that connects the myriad details of life, across all scales, to fundamental and universal physical principles.’ Center Fellows will be offered a competitive salary, travel funds, and independence to select a compelling line of research. The Center Fellow is not obligated to any particular faculty member, instead the Center exposes young physicists to problems posed by a wide range of living systems and gives them ‘considerable freedom to explore these problems, crossing boundaries among topics that would be in separate groups or departments at most institutions.’ This freedom is balanced by a support system as the Fellow is held accountable to formulating a feasible plan by interacting with senior Center faculty, and there’s a community of Fellows that provide peer advice and guidance.

Systems chemistry is a branch of chemical research that examines large, complicated chemical networks and focuses on understanding how complexity and function can emerge from the many diverse chemical interactions within the network. This grant provides support to a team led by Rein Ulijn, Professor of Physics and Director of the Nanoscience Initiative at the City University of New York Graduate Center, to induce a chemical system to demonstrate a life-like behavior; specifically, a primitive form of learning and memory. Dr. Ulijn’s basic chemical system will be composed of peptides (short proteins; a sequence of amino acids) that -with the help of an enzyme- can be reversibly combined into more complex peptides (oligopeptides). The team plans to expose a chemical network to a molecule that acts as an environmental stimulus that will cause a reaction, the formation of new peptide molecules and various phase-separated peptide ‘structures.’ After removing the stimulus molecules from the network, they will be re-introducing at some later time.  If the network responds more rapidly to the stimulus than when the molecules were first introduced, it has, in a basic sense, “remembered” the initial stimulus and ‘learned’ to respond faster.  The project begins by choosing an initial set of (2-6) interacting dipeptides. Molecular dynamics simulations will inform selection of the initial dipeptide system to ensure that the dipeptides have a propensity for self-assembly. This makes it likely that more complex peptides and (peptide) structures will form. Once an initial system has been selected, the researchers will synthesize the system in their lab, allow the peptide chemistry to run to a steady state, and then characterize the steady state distribution of peptides and phase-separated structures in the unperturbed system (i.e. before a stimulus molecule is introduced). The formation of oligopeptides and phase-separated structures will be monitored using a combination of microscopy, optical spectroscopy, liquid chromatography, mass spectrometry, and dynamic light scattering. Once the steady state properties of the unperturbed peptide system have been characterized, a stimulus molecule will be introduced and the researchers will characterize how the distribution of peptides and the formation of structures is modified. The characterization will be done for each of several stimulus molecules (flavor molecules grape, raspberry, banana and apple) selected based on their simplicity and because they offer a systematic variation in chemical-interaction potential.  Finally, the researchers will determine whether repeated exposure to a given stimulus molecule can condition the system to respond more rapidly; the stimulus molecules will be removed between exposures. The researchers will study how learning and memory are influenced by variation of experimental parameters such as pH, temperature, and molecular target concentration. They’ll also test the hypothesis that the physical basis of memory lies in remnant structures retained by the solution. This idea will be tested by using heat to melt any remnant structural nuclei; something that should eliminate any observed memory effects. Beyond demonstration of learning and memory induced by a single type of stimulus molecule, the researchers will also explore exposure to competing stimuli, by examining whether mixing of separately conditioned solutions yields a different response when compared to that obtained from a solution conditioned by simultaneous exposure to several types of stimulus molecules.

This grant supports a research team led by Amar Vutha, Professor of Physics at the University of Toronto, to search for evidence of new fundamental particles by making careful measurements of atomic nuclei. Professor Vutha will pursue a well-known particle discovery strategy -searching for so-called time symmetry violation in nuclei- but will pursue a new approach to performing the measurements. The new method is expected to improve nuclear time-symmetry-violation measurement precision by a factor of one hundred to one thousand. Time-reversal refers to negating time in the equations used to describe a physical system. Intuitively, it means that time flows backwards rather than forwards. Time-reversal symmetry means that particles follow the same equations irrespective of whether one runs the clock forward or backward (one can’t determine which way the clock runs by watching the particles). Many laws of microscopic physics are time-reversal invariant, but not all. More to the point for this project, the known sources of microscopic time-reversal asymmetry (T-violation) are inadequate to explain the observed matter/antimatter asymmetry of the universe and new particles that participate in T-violating interactions are needed to explain that asymmetry. The traditional approach to searching for new T-violating particles / interactions involves making measurements on a modest number of free neutrons or atoms. By contrast, Vutha will search for nuclear T-violation using an octupole deformed nucleus embedded within a solid-state crystal. There are three primary reasons this new approach could significantly improve nuclear T-violation measurement precision. First, atoms in a solid-state crystal are more highly compacted than free atoms (or neutrons) so many more atoms can be measured. This improves precision. Next, the atom proposed for these measurements has a spatially deformed (i.e. non-spherical) nucleus and this enhances sensitivity to nuclear T-violation by a factor of 100 to 1000. Finally, the solid-state crystal lattice has a large internal electric field, and this too enhances a T-violation signal. Grant funds will support three primary workflows: design and construction of the experimental apparatus, identification and mitigation of sources of statistical noise and systematic error, and the use of precision optical and radio-frequency spectroscopy to perform T-violation measurements on the system.

This grant supports a team at Imperial College London that aims to discover evidence for one or more new fundamental particles that may explain an important open question in physics: why the universe is filled with matter yet lacks antimatter. This question will be addressed by carefully measuring the shape of an electron – whether it’s round or aspherical – because an electron will be aspherical if it interacts with particles that treat matter and antimatter differently. These particles could explain the observed matter/antimatter asymmetry. Michael Tarbutt, a Professor of Physics at Imperial College London, will lead a five-year project to improve the relevant measurement precision by a factor of forty. The increased precision will either reveal evidence for one or more new fundamental particles, or set a new upper limit that constrains the properties of as-yet-undiscovered particles. The laws of physics treat matter and antimatter identically, and it’s thought that there were equal amounts of matter and antimatter immediately after the big bang, so the absence of antimatter in the universe is a deep mystery that challenges fundamental physics. The discovery of a new particle could explain this mystery, along with others such as the nature of dark matter. There are two leading detection approaches that achieve comparable precision. One approach measures a high density of neutral molecules for a brief time (milliseconds) as molecules move rapidly through a measurement apparatus; here, limited measurement time constrains achievable precision. The second approach measures static molecular ions for a relatively long time (seconds) and measurement precision is limited by the fact that ions cannot be tightly packed because they’re electrically charged, and they perturb one another. Professor Tarbutt proposes a new best-of-both-worlds approach: use molecules that are static so they can be measured for a long time, and neutral so they can be compacted to high density (measure many molecules). He aims to achieve this by performing an experiment using neutral molecules contained within an optical-trap. An optical-trap (or optical-lattice) is a type of container for atoms and molecules formed by overlapping several laser beams in a region of space.

Of the four fundamental forces in nature, three are well-described by quantum theory while the fourth — gravity — is not. Obtaining a unified theory that describes all four forces ranks among the most important goals in fundamental physics. Perhaps the most pressing question on the road to unification is whether gravity is a quantum force. Experiments that directly probe quantum gravity have been considered infeasible because the fundamental unit of ‘quantized’ space is exceedingly small. Directly probing this scale would require a particle accelerator the size of our galaxy. Instead, what physicists have been trying to do for many decades is to think of viable experiments that would teach us something about quantum gravity. Two recent papers envision just such an experiment.  That experiment, unfortunately, is not feasible given the limitations of current experimental physics. Yet there’s considerable optimism in some physics communities that these limitations may be overcome in the reasonably near future, perhaps in five to ten years. This grant provides funding to Gavin Morley, Professor of Physics at Warwick University, who is leading a collaboration that aims to tackle the primary challenges to performing the proposed experiment. Summarized broadly, what’s needed is the experimental capacity to create and manipulate large, heavy quantum systems and to arrange for conditions that allow gravity to be the dominant interaction between two laboratory-scale objects. In quantum physics, entanglement refers to a non-intuitive connection between objects that’s evidenced by measuring some property of the objects and showing that the measurements are more highly correlated than is allowed by classical physics. The proposed future experiment aims to determine whether two objects (diamonds) can become entangled via their mutual gravitational attraction. If they can, then gravity must be a quantum force, as asserted by two recently published papers. Morley and his team will address three lines of research critical to enabling that future quantum gravity experiment. First, it’s important that gravity be the dominant interaction between two objects, here micron-scale diamond samples (microdiamonds). Electromagnetism is much stronger than gravity so electromagnetic (EM) interactions must be heavily attenuated. The plan is to first measure the strength of EM interactions between two microdiamonds, and between a microdiamond and nearby experimental components. After measuring and understanding the sources of microdiamond EM interaction, the PIs will implement attenuation measures. Next, the researchers will demonstrate matter-wave interferometry involving objects much heavier than what’s been achieved to date. Heavy objects are required because the strength of gravity scales with mass so heavy objects are more easily entangled. Interferometry is required because the entanglement will be evidenced by a gravity-induced shift in the interference pattern. Morley will release a magnetically-levitated diamond and allow it to fall onto a laser-induced diffraction grating that creates a matter-wave interference pattern. By studying the ‘sharpness’ of the matter-wave interference pattern, Morley will learn about sources of ‘decoherence’ that limit how long the superposition lasts. Finally, the team will follow a protocol they’ve proposed to put a microdiamond into a spatial superposition of being in two places at once by using a laser to create a spin superposition (diamond simultaneously in two spin states) and then using a magnetic field to drive the two different spin components in opposite directions; thereby also achieving a spatial superposition. This will be done under conditions where EM forces are attenuated by rotating the diamond and by using a conductive screen.

General relativity—which explains gravity on large length and mass scales—and quantum mechanics—which explains the behavior of atoms and molecules--are our two most fundamental descriptions of nature. One of the most important unsolved problems in physics is uncovering the correct way to bring these two theories together. While theorists have proposed many possibilities, experiments are needed to guide the way. Relevant experimental data is hard to come by, however, because gravity is weak and extremely sensitive instruments are needed to detect its influence on (typically small) quantum systems. Funds from this grant support Jun Ye, Adjoint Professor of Physics at the University of Colorado at Boulder, to make improvements to the most precise instruments around—atomic clocks—and to then use these improved clocks to perform two types of laboratory-scale experiments: novel laboratory-scale tests of general relativity, and the first experiments where general relativity has measurable effects on the evolution of a quantum system. Starting with the first class of experiments, while general relativity (GR) has been tested previously, foundational GR principles are related to one another, making it challenging to test any one principle in isolation. Ye and his team will conduct atomic-clock-based measurements that will allow tests either of isolated principles or of the principles in different combinations as well as set  limits on parameters that can be used to develop GR-alternative theories. Principles to be tested include the Einstein Equivalence Principle; the Accelerated Clock Hypothesis; the equivalence of energy and mass; and the equivalence of gravitational and inertial mass. As to the second class of experiments, the improvements in atomic clocks will enable Ye and his team to perform measurements that probe the differential flow of time (GR time-dilation) across the wave function of a quantum system. Project theorists will compute the precise dynamics of such systems and help determine how they can best be detected using atomic clock methods. Ye’s efforts promise to improve the precision of atomic clocks by a factor of 10, achieve new standards of precision in measurements that employ quantum measurement protocols, and develop entirely new measurement protocols for detecting novel phenomena that arise at the interface of quantum physics and general relativity.

This grant supports efforts by Gurudev Dutt, Professor of Physics at the University of Pittsburgh, to improve experimental capabilities in physics to demonstrate quantum phenomena in increasingly large, heavy systems. Quantum phenomena, such as an object existing simultaneously in two places, are counterintuitive and have never been directly visualized because quantum states like superpositions have never been realized using macroscopic systems directly accessible to human senses. Why this is the case is a deep question in fundamental physics and falls under a field of research known as ‘quantum foundations.’ It’s thought that environmental interactions—bumping into a gas molecule or absorbing a photon of light—play an important role by destroying typically-fragile quantum states. Even assuming environmental isolation, however, a macroscopic quantum state may not be achievable, as gravitational interactions may destroy (decohere) the quantum state of a sufficiently heavy object. Experiments that work to create ever larger, heavier quantum states that last for increasingly long periods of time are needed to understand the practical and possibly fundamental limits to realizing macroscopic quantum states. Professor Dutt and collaborators are launching a project focused on creating and maintaining large, heavy quantum superpositions. While the work is of interest from a quantum foundations perspective, it’s also critical to enabling a future experiment capable of answering one of the most important open questions in physics: whether gravity is a quantum force.  Achieving large, heavy quantum superpositions stands as a major challenge that must be overcome to enable that experiment. Here the Dutt team intends to magnetically levitate a nanogram-mass, few-micron-sized diamond crystal and put it into a superposition state that lasts for about a second. Levitation under ultra-high vacuum conditions will provide a reasonable degree of environmental isolation for the diamond, and the proposed nanogram-scale superposition would be the heaviest quantum superposition achieved. To date, the heaviest object put into a quantum superposition suitable for matter-wave interferometry is about one million times less massive than the diamond Dutt and colleagues will target.  The Dutt team will first demonstrate a protocol for placing a diamond in a superposition of being in two places at once. In brief, a laser puts a microdiamond crystal into a spin superposition state (diamond simultaneously in two different spin states) and a magnetic field is then used to ‘transfer’ the spin superposition to a spatial superposition (diamond simultaneously in two different locations). Achieving a superposition lifetime of about a second will be challenging, in part due to the lack of good tools for measuring motional decoherence as this makes it difficult to assess the effectiveness of various measures aimed at extending motional coherence lifetimes. Dutt will test a new approach that leverages spin-based measurements to measure motional decoherence.  The team will also develop light-scattering-based and spectroscopy-based diamond-position monitors to directly measure motional noise. As a separate line of research, the research team will explore whether it’s possible to significantly increase superposition size by driving more than one spin excitation in a microdiamond.

Advances in AI and machine learning, and specifically large language models such as ChatGPT, Bard and Claude, herald a transformational period in access to knowledge.   This grant provides three years of support to the Wikimedia Foundation, the parent organization of Wikipedia, for a new initiative to harness these advances to improve Wikipedia’s core function—access to reliable knowledge for half a billion people each month—and to protect the largest encyclopedia in human history from vandalism and even potential obsolescence.  Planned activities over the grant period include the iterative improvement and user testing of a Wikipedia plug-in using ChatGPt—now available in an experimental beta version and generating 1000 queries per day; use of AI and machine learning tools to suggest valuable edits that human editors could use to improve articles; an improved open-source neural machine translation model that supports over 200 languages, significantly boosting Wikipedia’s translation capabilities; machine learning tools to help moderators filter bad edits; a machine learning model that will let volunteers build and host their own AI models and tools (versus those built by Wikipedia staff); and a new ML moderator tool called Automoderator that will defend against vandalism with automated prevention or reversion of bad edits.  Wikipedia staff will also experiment and observe the evolving ways that contributors, volunteers, donors, and users interact use AI tools to interact with the site and whether infrastructure changes are needed to accommodate chatbot use or other tools.