  Quantum computing holds a great promise and this work proposes to use new
quantum data networks (QDNs) to connect multiple small quantum computers to
form a cluster. Such a QDN differs from existing QKD networks in that the
former must deliver data qubits reliably within itself. Two types of QDNs are
studied, one using teleportation and the other using tell-and-go (TAG) to
exchange quantum data. Two corresponding quantum transport protocols (QTPs),
named Tele-QTP and TAG-QTP, are proposed to address many unique design
challenges involved in reliable delivery of data qubits, and constraints
imposed by quantum physics laws such as the no-cloning theorem, and limited
availability of quantum memory.
  The proposed Tele-QTP and TAG-QTP are the first transport layer protocols for
QDNs, complementing other works on the network protocol stack. Tele-QTP and
TAG-QTP have novel mechanisms to support congestion-free and reliable delivery
of streams of data qubits by managing the limited quantum memory at end hosts
as well as intermediate nodes. Both analysis and extensive simulations show
that the proposed QTPs can achieve a high throughput and fairness. This study
also offers new insights into potential tradeoffs involved in using the two
methods, teleportation and TAG, in two types of QDNs.
