  We consider the problems arising from the presence of Byzantine servers in a
quantum private information retrieval (QPIR) setting. This is the first work to
precisely define what the capabilities of Byzantine servers could be in a QPIR
context. We show that quantum Byzantine servers have more capabilities than
their classical counterparts due to the possibilities created by quantum
encoding procedures. We focus on quantum Byzantine servers that can apply any
reversible operation on their individual qudits. In this case, Byzantine
servers can generate any error, i.e., this covers \emph{all} possible single
qudit operations that can be applied by Byzantine servers on their qudits. We
design a scheme based on cross-subspace alignment (CSA) and we show that this
scheme achieves superdense coding gain in some cases.
