ICTS

If a set of massive objects collide in space and the fragments disperse, possibly forming black holes, then this process will emit gravitational waves. Computing the detailed gravitational wave-form associated with this process is a complicated problem, not only due to the non-linearity of gravity but also due to the fact that during the collision and subsequent fragmentation the objects could undergo complicated non-gravitational interactions. Nevertheless some results in quantum theory of gravity, known as soft graviton theorems, determine the power law fall-off of the wave-form at late and early times, including logarithmic corrections, in terms of only the momenta of the incoming and outgoing objects without any reference to what transpired during the collision. In this talk I shall explain the results and very briefly outline the derivation of these results.
 

Berry curvature physics and quantum geometric effects have been instrumental in advancing topological condensed matter physics. Although Landau level-based flat bands and conventional 3D solids have been pivotal in exploring rich topological phenomena, they are constrained by their limited ability to undergo dynamic tuning. By stark contrast, moiré systems have risen as a versatile platform for engineering bands and manipulating the distribution of Berry curvature in momentum space. These moiré systems not only harbour tunable topological bands, modifiable through a plethora of parameters, but also provide unprecedented access to large length scales and low energy scales. Furthermore, they offer unique opportunities stemming from the symmetry-breaking mechanisms and electron correlations associated with the underlying flat bands that are beyond the reach of conventional crystalline solids. A diverse array of tools, encompassing quantum electron transport in both linear and nonlinear response regimes provide direct avenues for investigating Berry physics in these materials [1].

I will discuss two experiments that use non-linear Hall response to probe Berry physics. In the first experiment first moment of Berry curvature helps probe valley Chern transitions [2]. In the second experiment we discuss the dynamic, but adiabatic, modulation of Berry curvature and it’s first moment [3].

[1] Adak et al. Nature Reviews Materials volume 9, 481 (2024).
[2] Sinha et al. Nature Physics 18, 765 (2022).
[3] Layek et al. unpublished

While the formulation of quantum mechanics predates computability theory, the idea of computers based on quantum physics only arose much later, in the 1980s. Initially studied only by the curious and intrepid, quantum computation, and quantum information processing in general, came into the limelight in the 1990s. The impetus, namely, the discovery of rigorous evidence of the advantage offered by quantum computers, culminating in the Shor algorithm for Integer Factorization, is now well-known. Since then, the field has been guided by the promise of new technology while also allowing for the pursuit of ideas unfettered by practical (or even physical) considerations. I will describe some of the advances in the field in the wake of these developments.

Quantum physics has reshaped our understanding of materials and created opportunities to design materials for novel device applications. For example, superconductivity, an emergent quantum phenomenon in which electrons move without dissipating energy, has been exploited for devices that enable quantum computing and communications. In addition, modern electronics rely heavily on technology that confines electrons in the interfacial layers of atoms, where the electrons move in an effective two-dimensional (2D) space, a flatland. The unique properties of these low-dimensional material systems are generally understood by considering enhanced quantum effects. In recent years, scientists have discovered that they can stack atomically thin 2D quantum materials to create engineered materials with a wide variety of electronic and optical properties. In this talk, we will discuss several research efforts to realize emergent physical phenomena in stacked atomically thin layered materials and possible applications based on these materials.

The characterization of identical quantum particles as bosons or fermions goes back to the early days of quantum mechanics. It was realized much later that in two space dimensions, particles with any statistics (`anyons') can exist. Such particles can emerge as quasiparticles in quantum phases of matter. The prime experimental example is in the Fractional Quantum Hall Effect (FQHE). After a brief review of the FQHE, I will discuss recent developments on the observation of the phenomenon in zero magnetic field, and the associated questions and opportunities.

Starting in the mid-1980s with the quantum control and detection of individual atoms/ions, we now have access to a variety of controllable quantum systems. One particular platform which has emerged as a popular choice is superconducting electrical circuits operating at ultra-low temperatures. These are micro to nanoscale electrical circuits that can be engineered to show quantum mechanical phenomena like superposition and entanglement. In this talk, I will introduce the concept of a quantum electrical circuit and how one can use superconducting materials to build them. The flexibility in circuit design allows one to create near ideal custom Hamiltonians which can be used to implement textbook measurements and explore various phenomena in previously unexplored regimes. The same flexibility also enables the possibility of large-scale chips for quantum computing applications. I will discuss some examples to illustrate the versatility of this platform and also highlight the various challenges in building a practical quantum computer.

Quantum simulation has emerged as a new and interdisciplinary research field that enables a microscopic view of quantum matter both in and out of equilibrium across different physical platforms. Recent applications of quantum simulations involving strongly correlated electronic systems using ultracold atoms in optical lattices and tweezers will be outlined. By comparing with state-of-the-art numerical methods, we show that quantum simulations with fermionic atoms can provide highly valuable and novel insights into the understanding of strongly correlated matter. As an example, we present an analysis of the emergence of the pseudogap phase in the fermionic Hubbard model. We identify a novel universal behavior of magnetic correlations upon entering the pseudogap phase, observed in both spin-spin and higher-order spin-charge correlations.

In addition to analog methods, gate-based fermionic quantum computing offers distinct advantages in quantum computations. We demonstrate the elementary operations required to manipulate the orbital degrees of freedom, which form the basis of a fermionic quantum computer.

Ordered phases of matter have close connections to computation. Two prominent examples are spin glass order, with wide-ranging applications in machine learning and optimization, and topological order, closely related to quantum error correction. Here, we introduce the concept of topological quantum spin glass (TQSG) order which marries these two notions, exhibiting both the complex energy landscapes of spin glasses, and the quantum memory and long-range entanglement characteristic of topologically ordered systems. Our work introduces a topological analog of spin glasses that preserves quantum information and displays robust many-body entanglement even at finite temperatures, opening new avenues for both statistical mechanics and quantum computer science.