Protocols for Packet Quantum Network Intercommunication

A quantum network, which involves multiple parties pinging each other with quantum messages, could revolutionize communication, computing, and basic sciences. The future internet will be a global system of various packet switching quantum and classical networks, and we call it quantum internet . To build a quantum Internet, unified protocols that support the distribution of […]

Efficient Optimization of Cutoffs in Quantum Repeater Chains

Quantum communication enables the implementation of tasks that are unachievable with classical resources. However, losses on the communication channel preclude the direct long-distance transmission of quantum information in many relevant scenarios. In principle, quantum repeaters allow one to overcome losses. However, realistic hardware parameters make long-distance quantum communication a challenge in practice. For instance, in […]

Enhanced Uplink Quantum Communication With Satellites via Downlink Channels

In developing the global quantum Internet, quantum communication with low-earth-orbit satellites will play a pivotal role. Such communication will need to be two way: effective not only in the satellite-to-ground (downlink) channel but also in the ground-to-satellite channel (uplink). Given that losses on this latter channel are significantly larger relative to the former, techniques that […]

Quantum Approximate Optimization With Parallelizable Gates

The quantum approximate optimization algorithm (QAOA) has been introduced as a heuristic digital quantum computing scheme to find approximate solutions of combinatorial optimization problems. We present a scheme to parallelize this approach for arbitrary all-to-all connected problem graphs in a layout of quantum bits (qubits) with nearest-neighbor interactions. The protocol consists of single qubit operations […]

Entanglement Distribution in a Quantum Network: A Multicommodity Flow-Based Approach

We consider the problem of optimizing the achievable EPR-pair distribution rate between multiple source-destination pairs in a quantum Internet, where the repeaters may perform a probabilistic Bell-state measurement and we may impose a minimum end-to-end fidelity as a requirement. We construct an efficient linear programming (LP) formulation that computes the maximum total achievable entanglement distribution […]

High-Dimensional Semiquantum Cryptography

A semiquantum key distribution (SQKD) protocol allows two users, one of whom is restricted in their quantum capabilities to being nearly classical, to establish a shared secret key, secure against an all-powerful adversary. The study of such protocols helps to answer the fundamental question of “how quantum” must a protocol be to gain an advantage […]