Quantum Protocol Distills Entangled Pairs with Improved Rates on Hardware Device

The quest to build practical quantum communication networks relies on efficiently creating and sharing entangled particles, but maintaining this delicate quantum state is challenging. Alexander Greenwood, Jackson Russett, and Hoi-Kwong Lo, from the University of Toronto, alongside colleagues, now demonstrate a significant step forward in this area by successfully implementing a technique called random party distillation on a superconducting quantum processor. This process effectively extracts high-quality entangled pairs from a more complex, multi-particle state, and the team achieves distillation rates exceeding previous benchmarks. By performing this protocol on actual quantum hardware, the researchers not only validate the method but also gain valuable insights into how errors arising from the measurement process can be overcome, bringing us closer to robust and scalable quantum communication.

Researchers have successfully demonstrated an improved method for extracting entangled pairs of qubits from a multi-qubit state, a process known as random party distillation. This advancement builds upon existing quantum information protocols and offers a pathway to enhance the distribution of entanglement, particularly in systems where direct qubit connections are limited. The team implemented this protocol on IBM’s quantum hardware, achieving distillation rates exceeding those previously reported, specifically generating 0.81 entangled pairs per initial multi-qubit state. The protocol proceeds in rounds, with each round attempting to isolate an entangled pair; if successful, the process ends, otherwise, it repeats.

A key innovation is the inclusion of a final, strong measurement step, which increases the overall probability of successfully obtaining an entangled pair, even after multiple rounds of weaker measurements. The researchers optimized the strength of the measurements in each round, dynamically adjusting them to maximize the probability of distillation, and calculations show the success probability increases with the number of rounds. Importantly, the protocol is robust enough to function even with imperfect initial states, a crucial consideration for current quantum hardware. The experiment was conducted on a 127-qubit processor, demonstrating the protocol’s applicability to real-world quantum systems.

The team addressed challenges posed by the hardware, such as qubit decoherence during measurements, by employing error mitigation techniques, highlighting the potential of random party distillation for building more robust and scalable quantum communication networks. This work demonstrates that the fidelity of the resulting entangled states consistently surpassed that of the initial state, even after the first round of the distillation protocol. Results indicate an average distilled entanglement of 0. 5311 pairs per initial state for a single-round implementation, and the study quantified the performance of the protocol by calculating a lower bound for the entanglement of formation, a measure of the degree of entanglement. While the performance decreases with successive rounds, the demonstrated improvements in distillation rates represent a significant step towards realizing practical quantum information processing.