Ultra-low switching Energy Memories to artificial neurons
Memory devices are responsible for a significant fraction of the energy consumed in electronic systems- typically 25% in a laptop and 50% in a server station. Reducing the energy consumption of memories is an important goal. For the evolving field of artificial intelligence, the compatible devices must simulate a neuron. We are working on three different approaches towards these problems- one involving an organic metal centred azo complex, the other involving oxide based ferroelectric tunnel junctions and the last involving real live neuronal circuits.
The one-electron model of graphene: A mathematical perspective
The talk presents theorems comparing continuum one-electron models of graphene with tight binding and other approximations. Joint work with Micael Weinstein, James Lee-Thorp and Jacob Shapiro.
A bilayer Hubbard model with ultracold atoms.
Fermionic atoms in optical lattices have served as a useful model system in which to study and emulate the physics of strongly correlated matter. Driven by the advances of high-resolution microscopy, the current research focus is on two-dimensional systems, in which several quantum phases—such as antiferromagnetic Mott insulators for repulsive interactions and charge-density waves for attractive interactions—have been observed.
Generation of pure quantum light in the solid-state
The ability to generate light in pure quantum states is central to the development of quantum-enhanced technologies. Recently, artificial atoms in the form of semiconductor quantum dots have emerged as an excellent platform for quantum light generation [1]. By placing the quantum dot in an optical microcavity, pure dephasing phenomena are strongly suppressed and single photon wavepackets with very high quantum purity in the frequency domain are generated [2].
Observation of a dynamical purification phase transition in a trapped-ion quantum computer
When measurements are interspersed in random quantum circuits, the long-time entanglement of the system exhibits a phase transition with the varying density of measurements. With high measurement rates, a "pure'' phase emerges where the measurements rapidly project the system into a deterministic state, conditioned on the measurement outcomes. However, in the "mixed'' phase, the dynamics successfully encode quantum information from the initial state into a quantum error correcting code-space. This "purification phase transition" is reminiscent of a fault-tolerant threshold.
Nucleon and nuclear structure from measurements in muonic and normal atoms
Laser spectroscopy of simple atoms is sensitive to properties of the atomic nucleus, such as its charge and magnetization distribution, or its polarizability. This allows determining the nuclear parameters from atomic spectroscopy, but also limits the attainable precision for the determination of fundamental constants or the test of QED and the Standard Model.
Topological Quantum Matter
Electrons organize in ways to give rise to distinct phases of matter such as insulators, metals, magnets or superfluid or superconductors. In the last ten years or so, it has become increasingly clear that in addition to the symmetry-based classification of matter, topological consideration of wavefunctions plays a key role in determining distinct or new quantum phases of matter [see, for an introduction, Hasan & Kane, Reviews of Modern Physics 82, 3045 (2010)].
Optimal State Transfer and Entanglement Generation in Power-law Interacting Systems
We present an optimal protocol for encoding an unknown qubit state into a multiqubit Greenberger-Horne-Zeilinger-like state and, consequently, transferring quantum information in large systems exhibiting power-law (1/r^α) interactions. For all power-law exponents α between d and 2d+1, where d is the dimension of the system, the protocol yields a polynomial speedup for α>2d and a superpolynomial speedup for α≤2d, compared to the state of the art.
Quantumness in the physics of AC electric power grids
Covering areas as large as entire continents, high-voltage power grids have a priori little to do with quantum mechanics. Yet, upon closer inspection, interesting analogies emerge with quantum / wave-coherent phenomena such as the Josephson effect, vortices in superfluids or multiple coherent scattering. This is so, because the operational state of AC power grids is determined by complex voltages at buses on a two-dimensional network.
Internally engineered Majorana modes in twisted bilayer graphene
Twisted bilayer graphene (TBG) realizes an exquisitely tunable, strongly interacting system featuring superconductivity and various correlated insulating states. In this talk I will introduce gate-defined wires in TBG as an enticing platform for Majorana-based fault-tolerant qubits. Our proposal notably relies on “internally” generated superconductivity in TBG – as opposed to “external” superconducting proximity effects commonly employed in Majorana devices – and may operate even at zero magnetic field.