Continuously Distributing Entanglement in Quantum Networks with Regular Topologies

Abstract

Small interconnected quantum processors can collaborate to tackle quantum computational problems that typically demand more capable devices. These linked processors, referred to as quantum nodes, can use shared entangled states to execute nonlocal operations. As a consequence, understanding how to distribute entangled states among nodes is essential for developing hardware and software. We analyze a protocol where entanglement is continuously distributed among nodes that are physically arranged in a regular pattern: a chain, a honeycomb lattice, a square grid, and a triangular lattice. These regular patterns allow for the modular expansion of networks for large-scale distributed quantum computing. Within the distribution protocol, we investigate how nodes can optimize the frequency of attempting entanglement swaps, trading off multiple entangled states shared with neighboring nodes for fewer states shared with non-neighboring nodes. We evaluate the protocol's performance using the virtual neighborhood size -- a metric indicating the number of other nodes with which a given node shares entangled states. Employing numerical methods, we find that nodes must perform more swaps to maximize the virtual neighborhood size when coherence times are short. In a chain network, the virtual neighborhood size's dependence on swap attempt frequency differs for each node based on its distance from the end of the chain. Conversely, all nodes in the square grid exhibit a qualitatively similar dependence of the virtual neighborhood size on the swap frequency.

8 pages main text with 4 figures; 11 pages appendices with 7 figures; v2: minor main text refinements (more concise introduction with added reference, more complete discussion), typos corrected

References in corpus (28)

• The Quantum Internet
• Quantum cryptography: Public key distribution and coin tossing
• Long-distance quantum communication with atomic ensembles and linear optics
• Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
• Quantum Teleportation is a Universal Computational Primitive
• Heralded entanglement between solid-state qubits separated by 3 meters
• Violation of Bell inequalities by photons more than 10 km apart
• Realization of a multi-node quantum network of remote solid-state qubits
• Distributed Quantum Computation over Noisy Channels
• Unconditional quantum teleportation between distant solid-state qubits
• Deterministic delivery of remote entanglement on a quantum network
• Practical free-space quantum key distribution over 10 km in daylight and at night
• A 10-qubit solid-state spin register with quantum memory up to one minute
• Optimal local implementation of non-local quantum gates
• Distributed Quantum Computation Based-on Small Quantum Registers
• Multiplexed Memory-Insensitive Quantum Repeaters
• High-rate, high-fidelity entanglement of qubits across an elementary quantum network
• 3/4-efficient Bell measurement with passive linear optics and unentangled ancillae
• On the waiting time in quantum repeaters with probabilistic entanglement swapping
• Experimental demonstration of entanglement delivery using a quantum network stack
• Tools for quantum network design
• Practical figures of merit and thresholds for entanglement distribution in quantum networks
• Bell-state measurement exceeding 50% success probability with linear optics
• Parameter regimes for a single sequential quantum repeater
• Optimal entanglement swapping in quantum repeaters
• Optimal entanglement distribution policies in homogeneous repeater chains with cutoffs
• Analytical Methods for High-Rate Global Quantum Networks
• Performance metrics for the continuous distribution of entanglement in multi-user quantum networks