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We present results on the digital quantum simulations of beam-splitter and squeezing interactions. The bosonic Hamiltonians are mapped to qubits and then digitalized in order to implement them in the IBM quantum devices. We use error mitigation and postselection to achieve high-fidelity digital quantum simulations of single-mode and two-mode interactions, as evinced-where possible-by full tomography of the resulting states. We achieve fidelities above 90% in the case of single-mode squeezing with low squeezing values and ranging from 60% to 90% for large squeezing and in the more complex two-mode interactions.

The generation of photons from the vacuum by means of the movement of a mirror is known as the dynamical Casimir effect (DCE). In general, this phenomenon is effectively described by a field with time-dependent boundary conditions. Alternatively, we introduce a microscopic model of the DCE capable of capturing the essential features of the effect with no time-dependent boundary conditions. Besides the field, such a model comprises a subsystem representing the mirror's internal structure. In this work, we study one of the most straightforward mirror systems: a qubit moving in a cavity and coupled to one of the bosonic modes. We find that under certain conditions on the qubit's movement that do not depend on its physical properties, a large number of photons may be generated without changing the qubit state, as should be expected for a microscopic model of the mirror.

We explore the interplay between acceleration radiation and the dynamical Casimir effect (DCE) in the field of superconducting quantum technologies, analyzing the generation of entanglement between two qubits by means of the DCE in several states of qubit motion. We show that the correlated absorption and emission of photons is crucial for entanglement, which in some cases can be linked to the notion of simultaneity in special relativity. I.arXiv:1812.08554v2 [quant-ph]