  We find a regularized formula for the entanglement-assisted (EA) capacity
region for quantum multiple access channels (QMAC). We illustrate the capacity
region calculation with the example of the collective phase-flip channel which
admits a single-letter characterization. On the way, we provide a
first-principles proof of the EA coding theorem based on a packing argument. We
observe that the Holevo-Schumacher-Westmoreland theorem may be obtained from a
modification of our EA protocol. We remark on the existence of a family
hierarchy of protocols for multiparty scenarios with a single receiver, in
analogy to the two-party case. In this way, we relate several previous results
regarding QMACs.
