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)].
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.
Dissipative phase transitions and autonomous error correction
Quantum phase transitions are ubiquitous in nature and come in a variety of flavors, including symmetry-breaking transitions and symmetry-protected topological transitions. While these paradigms are by now well understood for closed systems, their generalization to dissipative open systems remains largely unexplored. In this talk, I describe recent progress in this direction. This task has practical relevance: A non-trivial phase can be characterized by an emergent steady state degeneracy in the thermodynamic limit, which is the key ingredient for "autonomous" error correction.
Novel Clocks for New Physics Searches
The development of atomic clocks with systematic uncertainties in the 10-18 range enables searches for the variation of fundamental constants, dark matter, and violations of Lorentz invariance. I will give an overview of dark matter searches and other fundamental physics studies with atomic and nuclear clocks and focus on development of clocks with the highest sensitivities to new physics. I will discuss recent advances in theory of novel clocks based on highly-charged ions and efforts to develop a nuclear clock.
Experiments on superconducting processors at the dawn of NISQ era
The recent successful computation beyond the capability of classical computers has brought considerable attention to the Noisy Intermediate Scale Quantum (NISQ) processors. The only way to evaluate the promise of NISQ devices is to implement algorithms on them that are of interest to the scientific community.
Quantum Optics and Applications with Cooperative 2D Arrays
The physics of cooperative atoms/radiators in regular 2D arrays is dominated by two properties: first, a strongly frequency-selective reflectivity and second, the ability to confine polariton modes cleanly on the surface. This makes such a system highly sensitive to and controllable by light fields. Applications of these systems include quantum information, metrology, and nonlinear single-photon techniques.