Synchronized bursts of productivity and success in individual careers.

Notwithstanding a significant understanding of epidemic processes in biological, social, financial, and geophysical systems, little is known about contagion behavior in individual productivity and success. We introduce an epidemic model to study the contagion of scholarly productivity and YouTube success. Our analysis reveals the existence of synchronized bursts in individual productivity and success, which are likely mediated by sustained flows of information within the networks.

Waveform Estimation from Approximate Quantum Nondemolition Measurements.

With the advent of gravitational wave detectors employing squeezed light, quantum waveform estimation-estimating a time-dependent signal by means of a quantum-mechanical probe-is of increasing importance. As is well known, backaction of quantum measurement limits the precision with which the waveform can be estimated, though these limits can, in principle, be overcome by "quantum nondemolition" (QND) measurement setups found in the literature. Strictly speaking, however, their implementation would require infinite energy, as their mathematical description involves Hamiltonians unbounded from below. This raises the question of how well one may approximate nondemolition setups with finite energy or finite-dimensional realizations. Here we consider a finite-dimensional waveform estimation setup based on the "quasi-ideal clock" and show that the estimation errors due to approximating the QND condition decrease slowly, as a power law, with increasing dimension. As a result, we find that approximating QND with this system requires large energy or dimensionality. We argue that this result can be expected to also hold for setups based on truncated oscillators or spin systems.