Circuit quantum electrodynamics allows spatially separated superconducting qubits to interact via a "quantum bus", enabling two-qubit entanglement and the implementation of simple quantum algorithms. We combine the circuit quantum electrodynamics architecture with spin qubits by coupling an InAs nanowire double quantum dot to a superconducting cavity. We drive single spin rotations using electric dipole spin resonance and demonstrate that photons trapped in the cavity are sensitive to single spin dynamics. The hybrid quantum system allows measurements of the spin lifetime and the observation of coherent spin rotations. Our results demonstrate that a spin-cavity coupling strength of 1 MHz is feasible.
We demonstrate quantum control and entanglement generation using a Landau-Zener beam splitter formed by coupling two transmon qubits to a superconducting cavity. Single passage through the cavity-mediated qubit-qubit avoided crossing provides a direct test of the Landau-Zener transition formula. Consecutive sweeps result in Landau-Zener-Stückelberg interference patterns, with a visibility that can be sensitively tuned by adjusting the level velocity through both the non-adiabatic and adiabatic regimes. Two-qubit state tomography indicates that a Bell state can be generated via a single passage, with a fidelity of 78% limited by qubit relaxation.
The transition from elastic to plastic deformation in crystalline metals shares history dependence and scale-invariant avalanche signature with other non-equilibrium systems under external loading such as colloidal suspensions. These other systems exhibit transitions with clear analogies to work hardening and yield stress, with many typically undergoing purely elastic behavior only after 'training' through repeated cyclic loading; studies in these other systems show a power-law scaling of the hysteresis loop extent and of the training time as the peak load approaches a so-called reversible-toirreversible transition (RIT). We discover here that deformation of small crystals shares these key characteristics: yielding and hysteresis in uniaxial compression experiments of single-crystalline Cu nano-and micro-pillars decay under repeated cyclic loading. The amplitude and decay time of the yield precursor avalanches diverge as the peak stress approaches failure stress for each pillar, with a power-law scaling virtually equivalent to RITs in other nonequilibrium systems.The mechanical deformation of macroscopic metals is usually characterized by the yield stress, below which the metal responds elastically, and beyond which plastic deformation is mediated by complex dislocation motion and interactions. In small-scale crystals, dislocation activities manifest as avalanches, with characteristic discrete strain bursts in the stress-strain response of the sample [1-3]. The avalanches exhibit complex scale invariant behavior on wide length scales and time scales [3,4]. The yield stress depends on the history of the sample: if the sample were unloaded and then reloaded during plastic flow, the previous maximum stress would become the current yield stress, below which there are no deviations from linear-elastic response, with the flow and yield stresses always increasing, i.e. work hardening [5]. The elasticto-plastic transition in crystals finds theoretical analogies to many non-equilibrium material systems [6]: dilute colloidal suspensions [7,8], plastically-deformed amorphous solids [9][10][11][12], granular materials [13][14][15], and dislocationbased simulations of crystals [16]. In all these other systems, the loading-unloading hysteresis disappears only after repeated cycling to the maximum stress, coined as material training. These systems exhibit power laws and scaling in the limit that the maximum stress approaches a critical value, the so-called reversible-irreversible transition (RIT), which separates trainable and untrainable regimes. For crystals, the nonelastic reloading behavior is in reminiscence of fatigue, in which plastic training is characterized by cyclic strain hardening, an evolution of hysteresis loops, and the emergence of well-defined dislocation microstructures [17,18]. However, the immediate elastic-nonelastic asymmetry in the unloading-reloading process lies in the realm of abnormal fatigue behavior, such as the anomalous Bauschinger effect, which has only been observed before in polycrystalline me...
Contradictory scaling behavior in experiments testing the principle of universality may be due to external oscillations. Thus, the effect of damped oscillatory external forces on slip avalanches in slowly deformed solids is simulated using a mean-field model. Akin to a resonance effect, oscillatory driving forces change the dynamics of avalanches with durations close to the oscillation period. This problem can be avoided by tuning mechanical resonance frequencies away from the range of the inverse avalanche durations. The results provide critical guidance for experimental tests for universality and a quantitative understanding of avalanche dynamics under a wide range of driving conditions. IMPACT STATEMENT Simulations of deformation show how commonly neglected errant oscillations distort the dynamics of discrete plastic events and how the effects of these oscillations can be mitigated in experiments and applications.
We observe two distinct interevent time patterns in the slip avalanches of compressed bulk metallic glasses (BMGs). Small slip avalanches cluster together in time, but large slip avalanches recur roughly periodically. We compare the timing patterns of BMG slip avalanches with timing patterns of earthquakes and with the predictions of a mean-field model. The time clustering of small avalanches is similar to the known time clustering of earthquake foreshocks and aftershocks.
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