In this seminar, how coherent electromagnetic radiation at Tera-Hertz and mid-infrared frequencies can be used to drive complex solids, in an attempt to enhance their coherence, is discussed.
As collective excitations are driven nonlinearly, leading to coupling amongst otherwise virtually non-interacting normal modes of the material. Driving gives rise to non-thermal states with unconventional properties, and sometimes with emergent order. Interesting examples involve the nonlinear control of the crystal lattice, used to induce magnetic order, ferroelectricity and non-equilibrium superconductivity at high temperatures.

One ingredient that is necessary to achieve effective quantum computation is the ability to prepare high fidelity quantum registers. In this seminar, two distinct approaches that we have taken to address this problem will be discussed. The first approach comes from quantum information theory flavour, and is based on “dynamic cooling” whereby one qubit is cooled down at the expense of heating up N extra qubits, by means of a global, properly engineered unitary evolution. We demonstrated the method by implementing it on a current quantum computer (IBM’s). The downside of this and similar single qubit preparation methods is that they scale terribly when applied to the preparation of many qubits. The second approach comes from statistical mechanical flavour, and it bypasses this issue by addressing the quantum register as a whole. The idea is to take advantage of emergent cooperative effects (specifically the phenomenon of spontaneous symmetry breaking) combined with quantum phenomena (e.g. quantum tunneling) to reach high fidelity preparation of large registers. We implemented it on a current quantum hardware (D-wave) and demonstrated the joint preparation of about 5k qubits with the unprecedented global fidelity of 99,5%.

In this talk I will overview an ongoing project which revolves around the problem of defining QFTs on a non-Hausdorff spacetime. After a brief review of the locally-covariant formalism for QFT on curved spacetimes, we will spend some time understanding the “adjunction formalism” of non-Hausdorff differential geometry. In particular, we will see that ordinary globally-hyperbolic spacetimes can be “glued together” in order to describe non-Hausdorff spacetimes that exhibit topology change. Interestingly, this is in stark contrast to the usual version of topology change: in the non-Hausdorff case, our spacetime will be covered by a preferred set of globally-hyperbolic (Hausdorff) submanifolds, which doesn’t happen in the Hausdorff case. Once this observation is understood, we will see that the formalism of non-Hausdorff geometry seems to naturally cohere with locally covariant QFT: the QFTs on a non-Hausdorff spacetime can be described by “gluing together” QFTs defined on maximal globally-hyperbolic Hausdorff submanifolds. Time permitting, we will finish with an example of the Klein-Gordon field on a non-Hausdorff background, as well as some interesting observations for the near-future.

The development of fast and efficient quantum batteries is crucial for the prospects of quantum technologies. We show that both requirements are accomplished in the paradigmatic model of a harmonic oscillator strongly coupled to a highly non-Markovian thermal reservoir. At short times, a dynamical blockade of the reservoir prevents the leakage of energy towards its degrees of freedom, promoting a significant accumulation of energy in the battery with high efficiency. The evolution of the energy stored in the battery is almost periodic, which allows to avoid a too precise fine-tuning of the time at which the battery need to be disconnected from the charger. Moreover, our protocol is very efficient, allowing in principle to extract through unitary operations practically all the energy stored in the quantum battery, with a ratio between the energy that can be extracted and the work done by the charger which approaches the ideal unit limit. Our protocol may be envisioned with a quantum LC circuit playing the role of the battery and with the required environment being suitably engineered via state–of–the–art quantum circuits.