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Fabrication of superconducting nanomechanical resonators for quantum research, detectors and devices traditionally relies on a lithographic process, resulting in oscillators with sharp edges and a suspended length limited to a few 100 micrometres. We report a low-investment top-down approach to fabricating NbTi nanowire resonators with suspended lengths up to several millimetres and diameters down to 100 nanometres. The nanowires possess high critical currents and fields, making them a natural choice for magnetomotive actuation and sensing. This fabrication technique is independent of the substrate material, dimensions and layout and can readily be adapted to fabricate nanowire resonators from any metal or alloy with suitable ductility and yield strength. Our work thus opens access to a new class of nanomechanical devices with applications including microscopic and mesoscopic investigations of quantum fluids, detecting dark matter and fundamental materials research in one-dimensional superconductors in vacuum., Comment: 19 pages, 4 figures

In this note we present numerical study of spin dynamics of $\vartheta$-soliton in Homogeneously precessing domain (HPD) in superfluid $^3$He-B. The soliton consists of a small heavy core and long tails, in 1D simulation we observe their mutual motion. We also discuss mass density and tension of the soliton membrane and its 3D oscillations in a cylindrical cell., Comment: 6 pages, 6 figures

A time crystal is a macroscopic quantum system in periodic motion in its ground state, stable only if isolated from energy exchange with the environment. For this reason, coupling separate time crystals is challenging, and time crystals in a dynamic environment have yet not been studied. In our experiments, two coupled time crystals made of spin-wave quasiparticles (magnons) form a macroscopic two-level system. The two levels evolve in time as determined intrinsically by a nonlinear feedback. Magnons move from the ground level to the excited level driven by the Landau-Zener effect, combined with Rabi population oscillations. We thus demonstrate how to arrange spontaneous dynamics between interacting time crystals. Our experiments allow access to every aspect and detail of the interaction in a single run of the experiment, inviting technological exploitation-- potentially even at room temperature., Comment: 14 pages, 5 figures

Quantum time crystals are systems characterised by spontaneously emerging periodic order in the time domain. A range of such phases has been reported. The concept has even been discussed in popular literature, and deservedly so: while the first speculation on a phase of broken time translation symmetry did not use the name "time crystal", it was later adopted from 1980's popular culture. For the physics community, however, the ultimate qualification of a new concept is its ability to provide predictions and insight. Confirming that time crystals manifest the basic dynamics of quantum mechanics is a necessary step in that direction. We study two adjacent quantum time crystals experimentally. The time crystals, realised by two magnon condensates in superfluid $^3$He-B, exchange magnons leading to opposite-phase oscillations in their populations -- AC Josephson effect -- while the defining periodic motion remains phase coherent throughout the experiment., Comment: 7 pages, 2 figures