Fig. 3: A quantum switch in a star-shaped network topology as studied by Vardoyan et al.56.
From: NetSquid, a NETwork Simulator for QUantum Information using Discrete events
The switch (central node) is connected to a set of users (leaf nodes) via an optical fibre link that distributes perfect Bell pairs at random times, following an exponential distribution with mean rate μ ∝ e−βL, where L denotes the distance of the link and β the attenuation coefficient. Associated with each link there is a buffer that can store B qubits at each side of the link. As soon as n Bell pairs with different leaves are available, the switch performs a measurement in the n-partite Greenberger–Horne–Zeilinger (GHZ) basis, which results in an n-partite GHZ state shared by the leaves. The GHZ-basis measurement consists of: first, controlled-X gates with the same qubit as control; next, a Hadamard (H) gate on the control qubit; finally, measurement of all qubits individually. The figure shows four leaf nodes, GHZ size n = 3 and a buffer size B = 2.
