Abstract: From bio-physics to quantum simulators, many fields depend on sub-diffraction imaging of multiple point sources. Conventional wisdom suggests that using freely propagating waves to distinguish two or more identical, constantly scattering point sources is constrained by the diffraction limit.  As the separation between sources decreases, their diffraction patterns increasingly overlap, complicating individual identification.  We address this limitation by leveraging diffraction minima, rather than maxima, to image multiple sources simultaneously.  Our theoretical and experimental results demonstrate the ability to distinguish two point sources at 1/80th of the wavelength (approximately 8 nm in our case).  Contrary to expectations, our theory predicts improved measurement precision with decreasing distance between scatterers and increased scatterer density.  This breakthrough paves the way for resolving clusters of optical point scatterers at minuscule fractions of the wavelength, promising advancements in various scientific and technological domains.

Preprint: https://www.biorxiv.org/content/10.1101/2024.01.24.576982v1

Abstract: The search for novel quantum phases in 2D materials is rapidly expanding: It is driven by the interest in robust quantum anomalous Hall insulators, topological superconductivity, correlated electronic states, and fractional statistics and by the prospect of quantum simulation in solid state. Unconventional, inherently quantum behavior has been observed in layered and twisted graphene heterostructures, multilayered homo- and heterobilayer transition metal dichalcogenides (TMDs), in surface and quasi-2D layers in 3D materials, and nanopatterned devices. To progress further, the field relies on tunable systems to study phase transitions and on atomic resolution to correlate the phases with local physical and electronic properties.  In this colloquium, I will showcase recent developments in the field of tunable 2D platforms, highlighting twisted moiré systems, topological 2D materials, and atomic manipulation. Scanning tunneling microscopy (STM) has proved crucial for untangling competing quantum phases and deeply understanding the foundational elements driving their physics. Through high-resolution magnetic-field scanning tunneling spectroscopy, we have demonstrated the importance of the fine details of quantum geometry in these novel 2D platforms. Specifically, I will report on our discovery of the emergent anomalously large orbital magnetic susceptibility in twisted double bilayer graphene, along with the orbital magnetic moment. I will also discuss the potential in the field of quantum materials of combining STM, molecular beam epitaxy (MBE), and stacked 2D devices. As an example, I will present STM data on a back-gateable MBE-grown thin film of the quantum spin Hall insulator WTe2.

Abstract: Ultraviolet spectroscopy is one of the most powerful tools to cover a wide range of scientific fields, from planetary science to astronomy. We will introduce a future UV space telescope, LAPYUTA which is selected as a candidate for JAXA’s M-class mission.

LAPYUTA will accomplish the following four objectives, which are related to scientific goals: understanding the habitable environment and the origin of structure and matter in the universe. Objective 1 focuses on the subsurface ocean environments of Jupiter’s icy moons and the atmospheric evolution of the terrestrial planets. Objective 2 is to characterize the atmospheres of exoplanets around the habitable zone by detecting their exospheric atmospheres. Objective 3 will test whether the structures of present-day galaxies contain ubiquitous Lyα halos and reveal the physical origins of Lyα halos. Objective 4 elucidates the synthesis process of heavy elements from observations of ultraviolet radiation from hot gas immediately after neutron star mergers.

LAPYUTA will perform spectroscopic and imaging observations in the far ultraviolet spectral range (110-190 nm) with a large effective area (>300 cm^2) and a high spatial resolution (0.1 arcsec). LAPYUTA’s orbit is designed as an elliptical orbit with an apogee of about 2,000 km and a perigee of 1,000 km to avoid the influence of the geocorona when observing oxygen and hydrogen atoms and the Earth’s radiation belt. Launch is planned for the early 2030s.

Abstract:  We would like a theory of quantum gravity so that we can answer pesky questions, like “what really happens if I dive into a generic black hole?” However, we now have a solvable theory of quantum gravity in 1+1d, and we *still* are having trouble because it’s tricky to even formulate the questions properly. In this talk I will (1) explain why this is tricky, and (2) propose how we should be doing this systematically, arriving at concrete answers in this low dimensional gravity theory. This is based on work in progress with Andy Lucas.

Abstract:  I present evidence that electron-transfer in model organic photovoltaic blends can be modeled as a competition between short and long-range electron transfer events, each described by a Marcus parabola having different reorganization energies for the most localized charge-transfer (CT) state and the mobile free charge (CT) state. Time-resolved Microwave Conductivity (TRMC) combined with photoluminescence excitation (PLE), photoinduced-absorption detected magnetic resonance (PADMR), and femtosecond transient absorption (fsTA) spectroscopy show that when electron transfer is confined to the immediate interfacial region between the donor and the acceptor very little free charge is produced. Instead, excitons split into a highly localized charge transfer state that do not produce photoconductivity. These results provide an alternative way of thinking about charge separation in organic photovoltaic materials, unify solid-state and solution phase models of charge separation, and provide unique design rules for functional donor/acceptor interfaces.

Forthcoming.

Forthcoming.

Abstract forthcoming.

Forthcoming.

Abstract forthcoming.

Abstract: Empirical evidence for a gap between the computational powers of classical and quantum computers has been provided by experiments that sample the output distributions of two-dimensional quantum circuits. Many attempts to close this gap have utilized classical simulations based on tensor network techniques, and their limitations shed light on the improvements to quantum hardware required to frustrate classical simulability. In particular, quantum computers having in excess of ∼50 qubits are primarily vulnerable to classical simulation due to restrictions on their gate fidelity and their connectivity, the latter determining how many gates are required (and therefore how much infidelity is suffered) in generating highly-entangled states. Here, we describe recent hardware upgrades to Quantinuum's H2 quantum computer enabling it to operate on up to 56 qubits with arbitrary connectivity and 99.843(5)% two-qubit gate fidelity. Utilizing the flexible connectivity of H2, we present data from random circuit sampling in highly connected geometries, doing so at unprecedented fidelities and a scale that appears to be beyond the capabilities of state-of-the-art classical algorithms. The considerable difficulty of classically simulating H2 is likely limited only by qubit number, demonstrating the promise and scalability of the QCCD architecture as continued progress is made towards building larger machines.

Abstract: Superfluid helium-4 at millikelvin temperatures is an ideal acoustic medium, featuring ultralow dissipation and the unique possibility of tuning the mechanical frequency through pressurization. Combined with a cavity optomechanical readout to sensitively probe the motion, a superfluid resonant mass is a promising tabletop-scale platform to probe small mechanical signals and new physics, such as gravitational waves and dark matter. Previously, we demonstrated a prototype superfluid gravitational wave detector, setting the base for developing our Helium ultraLIght dark matter Optomechanical Sensor (HeLIOS). After reviewing superfluid optomechanical systems and motivating the detection of wavelike dark matter, I will present a recent characterization of our HeLIOS prototype. It promises unprecedented sensitivity and scalability to expand the search for dark matter, which nature is one of the biggest unsolved questions in modern science.

Abstract Forthcoming