Flight of a heavy particle nonlinearly coupled to a quantum bath

Fluctuation and dissipation are by-products of coupling to the `environment.'
The Caldeira-Leggett model, a successful paradigm of quantum Brownian motion,
views the environment as a collection of harmonic oscillators linearly coupled
to the system. However, symmetry considerations may forbid a linear coupling,
e.g. for a neutral particle in quantum electrodynamics. We argue that nonlinear
couplings can lead to a fundamentally different behavior. Specifically, we
consider a heavy particle quadratically coupled to quantum fluctuations of the
bath. In one dimension the particle undergoes anomalous diffusion, unfolding as
a power-law distribution in space, reminiscent of L\'{e}vy flights. We suggest
condensed matter analogs where similar effects may arise.