Suppressing the loss of ultracold molecules via the continuous quantum Zeno effect

We investigate theoretically the suppression of two-body losses when the
on-site loss rate is larger than all other energy scales in a lattice. This
work quantitatively explains the recently observed suppression of chemical
reactions between two rotational states of fermionic KRb molecules confined in
one-dimensional tubes with a weak lattice along the tubes [Yan et al., Nature
501, 521-525 (2013)]. New loss rate measurements performed for different
lattice parameters but under controlled initial conditions allow us to show
that the loss suppression is a consequence of the combined effects of lattice
confinement and the continuous quantum Zeno effect. A key finding, relevant for
generic strongly reactive systems, is that while a single-band theory can
qualitatively describe the data, a quantitative analysis must include multiband
effects. Accounting for these effects reduces the inferred molecule filling
fraction by a factor of five. A rate equation can describe much of the data,
but to properly reproduce the loss dynamics with a fixed filling fraction for
all lattice parameters we develop a mean-field model and benchmark it with
numerically exact time-dependent density matrix renormalization group
calculations.