We provide moment bounds for expressions of the type $$(X^{(1)} \otimes \cdots \otimes X^{(d)})^T A (X^{(1)} \otimes \cdots \otimes X^{(d)})$$
(
X
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1
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⊗
⋯
⊗
X
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d
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)
T
A
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X
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where $$\otimes $$
⊗
denotes the Kronecker product and $$X^{(1)}, \ldots , X^{(d)}$$
X
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,
…
,
X
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d
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are random vectors with independent, mean 0, variance 1, subgaussian entries. The bounds are tight up to constants depending on d for the case of Gaussian random vectors. Our proof also provides a decoupling inequality for expressions of this type. Using these bounds, we obtain new, improved concentration inequalities for expressions of the form $$\Vert B (X^{(1)} \otimes \cdots \otimes X^{(d)})\Vert _2$$
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B
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X
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2
.