may not always be the easiest option in experiments. We now demonstrate that it is also possible to study quantum spin fluctuations with single-component Bragg spectroscopy of a binary condensate. The single-component Bragg spectroscopy, corresponding to the single-component structure factor, can be calculated by restricting the integral of Eq. (\[Eq:SF\]) to the appropriate component, giving, for example, $$\begin{aligned}
S_1 &({\mathbf{k}_\rho},\omega) \\
 &= \sum_\kappa \Big| \int d^2{\boldsymbol\rho}e^{i{\mathbf{k}_\rho}\cdot{\boldsymbol\rho}} [u^\kappa_1({\boldsymbol\rho})+v^\kappa_1({\boldsymbol\rho})]\psi_1({\boldsymbol\rho})
 \Big|^2 \delta(\omega-\omega^\kappa) \notag .\end{aligned}$$ The one-component static structure factor then can be obtained as $S_1({\mathbf{k}_\rho}) = \int d\omega S_1({\mathbf{k}_\rho},\omega)$. The spin (solid), single-component (dot-dashed) and density (dashed) static structure factors are plotted in Fig. \[Fig:SFpeak\](a) for $g_{12}/g=1.51$ and $g=8$. As expected, $S_1$ provides an intermediate measure between the spin and density structure factors; while the peak is somewhat subdued it is still clearly visible. Figure \[Fig:SFpeak\](b) presents the spin (solid) and single-component (dot-dashed) structure factor peaks \[indicated by horizontal lines in Fig. \[Fig:SFpeak\](a)\] as a function of $g_{12}$. Here it can be seen that close to the immiscibility phase transition, which is at $g_{12}^{\rm c}=1.55$, the spin contribution dominates and $S_1$ provides an effective measure of the enhanced quantum spin fluctuations.

Experimental considerations {#Sec:ExpConsid}
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From a qualitative perspective we expect our results 