We study the capacity of quantum private information retrieval (QPIR) with multiple servers. In the QPIR problem with multiple servers, a user retrieves a classical file by downloading quantum systems from multiple servers each of which contains the copy of a classical file set while the identity of the downloaded file is not leaked to each server. The QPIR capacity is defined as the maximum rate of the file size over the whole dimension of the downloaded quantum systems. When the servers are assumed to share prior entanglement, we prove that the QPIR capacity with multiple servers is 1 regardless of the number of servers and files. We construct a rate-one protocol only with two servers. This capacity-achieving protocol outperforms its classical counterpart in the sense of capacity, server secrecy, and upload cost. The strong converse bound is derived concisely without using any secrecy condition. We also prove that the capacity of multi-round QPIR is 1.

翻译：我们用多个服务器研究量子私人信息检索能力。 在多个服务器的QPIR问题中, 用户从多个服务器下载量子系统, 获取一个古典文件, 每个服务器下载量子系统都包含古典文件集的复制件, 而下载文件的身份不泄露给每个服务器。 QPIR 能力的定义是下载量子系统整个维度的最大文件尺寸。 当假设服务器在被连接前共享时, 我们证明多个服务器的QPIR能力为1, 不论服务器和文件的数量。 我们只用两个服务器构建一个标准协议。 这个能力实现协议在能力、 服务器保密性和上传成本方面超越了它的古典对应方。 强反向连接在不使用任何保密条件的情况下以简洁的推导出。 我们还证明多轮QPIR 能力是1。