Quantum entanglement assisted with measurements provides various pathways to communicate information to parties within a network. In this work, we generalize a previous broadcasting protocol and present schemes to broadcast product and multipartite entangled quantum states, where in the latter case the sender can remotely add phase gates or abort distributing the states. We first focus on the broadcasting of product quantum states in a network, and generalize the basic protocol to include an arbitrary basis rotation and allow for multiple receivers and senders. We show how to add and delete senders from the network. The generalization also includes the case where a phase to be applied to the broadcast states is not known in advance but is provided to a sender encoded in another quantum state. Applications of broadcasting product states include authentication and three-state quantum cryptography. In the second part, we study the distribution of a single multiqubit state shared among several receivers entangled with multiqubit phase gates, which includes the graph states as an example. We show that by coordinating with the sender, the receivers can assist in performing remote, distributed measurement-based quantum computation with the Pauli-
X basis measurement alone. As another application of this, we discuss the distribution of the multiqubit Greenberger-Horne-Zeilinger state.
A general scheme for controlled teleportation of an arbitrary multi-qudit state with d -dimensional Greenberger–Horne–Zeilinger (GHZ) states is proposed. For an arbitrary m -qudit state, the sender Alice performs m generalized Bell-state projective measurements on her 2 m qudits and the controllers need only take some single-particle measurements. The receiver Charlie can reconstruct the unknown m -qudit state by performing some single-qudit unitary operations on her particles if she cooperates with all the controllers. As the quantum channel is a sequence of maximally entangled GHZ states, the intrinsic efficiency for qudits in this scheme approaches 100% in principle.
An unknown quantum operation, like an unknown quantum state, cannot be perfectly copied or stored for later use. A specific gate can be embedded in an entangled resource and teleported, but its destination is fixed when the resource is created. Here we show that the capability to apply a two-qudit entangling gate can instead be secret-shared among many parties: the shares are distributed in advance, and a later key release lets exactly one of them, chosen after distribution, exercise it. A provider encrypts half of a Bell pair held with a user into
n shares, one per candidate node. The selected node, given the key qudits, completes an exact non-local
CSUMk gate with the user's data, in every measurement branch and for any qudit dimension, with the power
k chosen by the user alone. Any coalition of fewer than
n candidate nodes, or the key register alone, holds no information, unselected nodes cannot tell whether a selection occurred, and the key cannot decrypt twice. For two candidates the registers form a
((3,5)) threshold scheme. Encoder and decoder are explicit
O(n) circuits. The construction supports jointly authorized and anonymous gate application, advancing distributed quantum computing and quantum network capabilities.
Abstract Quantum broadcast is a method for distributing known quantum information to multiple recipients at once. Although the no-cloning theorem prohibits copying unknown quantum states, it is still possible to transmit the same known state to different destinations. This research introduces two new approaches. The first approach allows a sender to broadcast a single qubit to n receivers using a specialized entangled state known as a 2 n -qubit cluster state. The paper illustrates this method with a detailed example for four receivers ( n = 4 ) and demonstrates its validity through implementation on the Qiskit platform. The second protocol, builds upon the first protocol and allows for broadcasting a particular class of n-qubit state to n receivers. The effects of different quantum noise types on the protocol are investigated, with the fidelity metric used to quantify the quality of broadcasted states over a noisy quantum channel. These new protocols offer more efficient ways to share quantum information, potentially paving the way for improved quantum communication networks and internet.