Qubits are the standard basis for quantum computation with many competing host platforms such as superconducting circuits, trapped ions, and quantum dots, to name a few. Part of the recent efforts with these platforms focused on simulations of fermionic systems. However, the mapping from qubits to local fermionic modes is inefficient because it introduces additional overhead to the calculations. To overcome this limitation, we propose a practical implementation of a universal quantum computer that uses local fermionic modes rather than qubits. Our design consists of quantum dots tunnel coupled by a hybrid superconducting island together with a tunable capacitive coupling between the dots. We show that coherent control of Cooper pair splitting, elastic cotunneling, and Coulomb interactions allows us to implement the universal set of quantum gates. Finally, we discuss possible limitations of the device and list necessary experimental efforts to overcome them. Particularly, we predict short coherence times due to charge noise and develop an alternative operational regime using neutral Andreev fermions.

The fluctuation relations, which characterize irreversible processes in Nature, are among the most important results in non-equilibrium physics. In short, these relations say that it is exponentially unlikely for us to observe a time-reversed process and, thus, establish the thermodynamic arrow of time pointing from low to high entropy. On the other hand, fundamental physical theories are invariant under time-reversal symmetry. Although in Newtonian and quantum physics the emergence of irreversible processes, as well as fluctuation relations, is relatively well understood, many problems arise when relativity enters the game. In this talk we explore the question of how the general relativistic effects enter into the fluctuation relations. We conclude that a positive entropy production emerges as a consequence of spacetime curvature.

Skyrmionics stands as one of physics' most promising areas, with the potential to innovate and develop future devices and technologies. Magnetic skyrmions are nanoscale magnetic whirls that are topologically protected and can be moved by currents, leading to the prediction of several applications. Its topological charge leads to high stability; however, it also leads to the skyrmion Hall effect. From memory storage devices, like the racetrack memory, to computing devices, like artificial neurons, this shortcoming is one of the primary reasons why skyrmion-based spintronic devices have yet to be achieved. Here, we study the motion of skyrmions with different topological charges and helicities. Using an effective center-of-mass description of these magnetic quasiparticles, namely, the Thiele equation, we analyze their dynamics under different gradient landscapes and interactions aiming to suppress or take advantage of the skyrmion Hall effect. Following a neuroscience approach, we also discuss possible applications in neuromorphic computing.

[1] I.R, de Assis, et al. Phys. Rev. B 108, 144438 (2023)
[2] I.R, de Assis, et al. Neuromorph. Comput. Eng. 3 014012 (2023)

Neuromorphic computing mimics the brain's architecture to create energy-efficient devices. Reconfigurable synapses are crucial for neuromorphic computing, which can be achieved through memory-resistive (memristive) switching. Graphene-based memristors have shown nonvolatile multi-bit resistive switching with desirable endurance. Through first-principles calculations, we study the structural and electronic properties of graphene in contact with an ultra-thin alumina overlayer and demonstrate how one can use charge doping to exert direct control over its interfacial covalency, reversibly switching between states of conductivity and resistivity in the graphene layer. We further show that this proposed mechanism can be stabilized through the p-type doping of graphene, e.g., by naturally occurring defects, the passivation of dangling bonds, or defect engineering.

Relevant reference: 10.1103/PhysRevResearch.5.043147

In this talk I will overview some of our recent works involving (i) the nonlocality of local Andreev conductances as a probe for topological Majorana wires in novel three-terminal superconducting 1D setups, asymmetrically coupled to normal leads [1], (ii) phase driving hole spin qubits in double quantum dots under simultaneous transverse (Rabi) and longitudinal (phase) drives [2], which enables tunable additional side bands and (some) immunity against noise, and (iii) beating-free magnetoresistitivity in 2D electron gases with strong (unmatched) spin-orbit and Zeeman interactions, in which a new condition for the vanishing of beatings is derived [3,4].  
 
*On leave from the University of São Paulo (IFSC).
[1] Dourado, Penteado, and Egues, arXiv:2303.01867.
[2] Bosco, Geyer, Camenzind, Eggli, Fuhrer, Warburton, Zumbühl, Egues, Kuhlmann, and Loss, arXiv:2303.03350, Phys. Rev. Lett., in press (Editors' suggestions).
[3] Candido, Erlingsson, Gramizadeh, Costa, Weigele, Zumbühl, and Egues, arXiv:2304.14327.
[4] Gramizadeh, Candido, Manolescu, Egues, and Erlingsson, arXiv:2306.02503.