  For quantum fluids, the role of quantum fluctuations may be significant in
several regimes such as when the dimensionality is low, the density is high,
the interactions are strong, or for low particle numbers. In this paper we
propose a fundamentally different regime for enhanced quantum fluctuations
without being restricted by any of the above conditions. Instead, our scheme
relies on the engineering of an effective attractive interaction in a dilute,
two-component Bose-Einstein condensate (BEC) consisting of thousands of atoms.
In such a regime, the quantum spin fluctuations are significantly enhanced
(atom bunching with respect to the noninteracting limit) since they act to
reduce the interaction energy - a remarkable property given that spin
fluctuations are normally suppressed (anti-bunching) at zero temperature. In
contrast to the case of true attractive interactions, our approach is not
vulnerable to BEC collapse. We numerically demonstrate that these quantum
fluctuations are experimentally accessible by either spin or single-component
Bragg spectroscopy, offering a useful platform on which to test
beyond-mean-field theories. We also develop a variational model and use it to
analytically predict the shift of the immiscibility critical point, finding
good agreement with our numerics.
