One of the most transformational outcomes promised by research in quantum information is a quantum computer that is exponentially faster than any classical computer. Current state-of- the-art quantum devices have not reached the level of complexity needed to demonstrate this capability, and alternative approaches may enable shortcut routes to achieving this exciting goal. Phonons, the quantum particles of sound waves in solids, represent the collective motion of astronomical numbers of atoms, and present an intriguing, completely solid-state approach to quantum information. Recent developments have shown that phonons can be used as carriers of quantum states, with properties very similar to photons. In this talk I will some of the results from my group’s research, where we use superconducting qubits for the on-demand generation, storage, and detection of individual microwave-frequency phonons in an acoustic resonator; use phonons to transmit quantum states and generate quantum entanglement; demonstrate a single-phonon interferometer and a quantum information process known as “quantum erasure”; and most recently demonstrate the acoustic Hong-Ou-Mandel effect with phonons, illustrating the wave-particle duality fundamental to quantum mechanics. Interestingly, this last development points to the possible development of a phonon-based version of linear optical quantum computing, which could be called linear mechanical quantum computing.

This presentation focuses into the exceptional capabilities of lead and tin halide perovskites, spotlighting their significant promise in fields such as photovoltaics and radiation detection. Central to our discussion is the pivotal role played by the lone pair of electrons on Pb2+ and Sn2+ ions, a factor that profoundly shapes the materials' physical characteristics. We will place a particular emphasis on the revolutionary contributions of both three-dimensional (3D) and two-dimensional (2D) perovskite structures to the future of optoelectronic devices. Additionally, the critical importance of synthesis methods in modifying these properties will be examined, showcasing how mastery over material creation can enhance device performance. By discussing the essential chemistry underlying these materials, the talk aims to forge a link between theoretical understanding and tangible technological advancements, as a way for significant progress in the field.

Zero-dimensional (0D) nanosized semiconductor crystals, presently known as colloidal quantum dots (QDs), are attractive materials for applications in laser technologies. In addition to being compatible with easily scalable chemical techniques, they offer multiple advantages derived from a 0D character of their electronic states including a size-tunable emission wavelength and a low optical-gain threshold. It has been more than three decades since the first demonstration of QD lasing [1]. These early studies employed CdSe nanocrystals embedded in a glass matrix – the samples akin to standard colored glass filters [2]. Following this discovery, it took three years to realize lasing with epitaxial QDs [3] and six more years to demonstrate the effect of amplified spontaneous emission (ASE) – a precursor of lasing – with colloidal QDs [4]. So far, all validated reports on colloidal QD lasing employed optically excited close-packed solid-state QD films. Two classes of QD lasers that are yet to be realized are liquid-state optically pumped devices and electrically pumped solid-state lasers (laser diodes). In both cases, a principal obstacle is very fast Auger recombination of optical-gain active multicarrier states. One consequence of fast Auger decay is the existence of a minimal (critical) QD concentration required for lasing. Due to solubility limits, this concentration is difficult to attain with liquid-state samples. Fast Auger delay also creates a serious problem when one tries to realize lasing with electrical pumping. In particular, it mandates the use of prohibitively high current densities for maintaining QDs in the inverted multicarrier state. Here we describe how we overcome the challenge of fast Auger recombination using meticulously engineered QDs [5,6]. To impede Auger decay, we modify an optical gain state such as to reduce the number of available Auger pathways. Further, we employ compositional grading of the QD interior to smoothen carrier confinement potentials and whereby suppress the strength of individual Auger transitions. As a result, our engineered QDs exhibit long optical gain lifetimes (nanosecond time scales) while still maintaining strong quantum confinement. We use our novel QDs to demonstrate new types of lasing devices including prototype laser diodes and widely tunable dye-like liquid-state lasers [5,6].

Meeting the escalating electricity demands of our advancing society, particularly at the terawatt scale, requires achieving high power conversion efficiency and low cost per peak watt in solar cell technology simultaneously. Prior to the introduction of perovskite solar cells, only a limited array of materials and technologies could meet both criteria. This presentation traces the evolution toward the development of practical solid-state perovskite solar cells. Beginning with an overview of initial technologies, the discussion progresses to the emergence of solid-state perovskite solar cells. Early efforts involved the use of quantum dot inorganic materials, such as nanocrystalline lead sulfide, as light harvesters. Despite their potential, these materials encountered significant challenges, primarily surface-defect- mediated recombination. Acknowledging these limitations, methylammonium lead triiodide (MAPbI 3 ) perovskite emerged as an alternative to inorganic quantum dots. However, initial implementations as sensitizers in liquid-electrolyte-contained structures yielded disappointing results, with efficiencies as low as 3-4% in 2009 and the dissolution of MAPbI 3 . A breakthrough occurred in 2012 when a pioneering study demonstrated a 9.7% efficient and 500-hour-stable perovskite solar cell, leveraging MAPbI 3 and a solid hole transporting material. This pivotal advancement rendered perovskite solar cells a viable and durable technology. Subsequent years witnessed rapid growth in perovskite photovoltaic research, with efficiencies exceeding 26% using FAPbI 3 , rivaling or surpassing existing technologies. Current research endeavors focus on enhancing stability and exploring tandem structures for electricity generation in both terrestrial and space applications. The perovskite solar cell stands poised as the most promising energy solution, with its potential impact on sustainable energy surpassing current expectations once stability and lead immobilization challenges are effectively addressed.

Organic mixed ionic/electronic conductors (OMIECs) have gained considerable interest in bioelectronics, power electronics, circuits and neuromorphic computing. These organic, often polymer-based, semiconductors rely on a combination of ionic transport, electronic transport, and high volumetric charge storage capacity. These properties enable new capabilities; for example, in the realm of bioelectronics, OMIEC-based electrochemical devices can efficiently amplify local bio-signals and can be engineered for spiking behavior to mimic basic neural pathways promising efficient biohybrid systems. However, despite recent progress and a rapidly expanding library of new materials, a full understanding of fundamental processes of OMIECs remains elusive. Critically, useful studies require us to probe these systems in device-relevant conditions, fully considering the effects of ions and solvent on microstructure and transport. To this end, we report on recent efforts towards structure/composition-property relations in high performance organic mixed conductors using ex-situ, in-situ, and operando scattering, spectroscopic, and gravimetric techniques. Such characterization tools open new avenues to understand and design more stable, high-performance materials and devices.