Faster entanglement prep with balanced gain and loss

Researchers at Zhengzhou University and collaborating institutions have demonstrated a method for creating entanglement in up to 10 qubits, overcoming a fundamental trade-off between the quality and speed of quantum connections. The work identifies that minimal evolution time is smaller for parity-time (PT) -symmetric systems compared to traditional approaches, achieving speedups of many orders of magnitude in two-qubit entanglement preparation. This advance utilizes active systems with balanced gain and loss, enabling maximal entanglement with rapid speed, high fidelity, and resilience against errors, highlighting the potential of these devices for diverse quantum resources.

PT-Symmetry Overcomes Entanglement-Fidelity Tradeoff

A previously accepted limitation in building quantum systems, the inverse relationship between how quickly entanglement forms and the reliability of that entanglement, has been overcome through the use of PT-symmetric systems, according to a new report. Researchers demonstrated a method for achieving both rapid entanglement and high fidelity, a combination previously thought unattainable, by leveraging systems with carefully balanced gain and loss. This advance addresses a critical problem often overlooked in quantum devices based on exceptional points, where dissipation significantly impacts fidelity.

The work details how two- to six-partite entanglement was successfully prepared as a demonstration of this principle, even when gain and loss were not perfectly balanced; this contrasts with previous passive PT-symmetric approaches. This acceleration stems from the unique properties of PT-symmetric systems near their exceptional points, or where spectral coalescence occurs.

The researchers highlight that this method is resilient against non-resonant and coupling strength errors, expanding the practical applications of these systems. Further validating the scalability of this approach, the team extended their success to preparing entanglement among ten qubits. This achievement demonstrates the generality of the method and its potential for building larger, more complex quantum systems. The paper states that they “identify an inherent trade-off relation between the degree of entanglement and fidelity, and demonstrate that this limitation can be effectively overcome,” emphasizing the significance of their findings.

The study was conducted by Bingbing Liu, Shilei Su, and colleagues from institutions including Zhengzhou University and the Henan Academy of Sciences in China, as well as RIKEN in Japan and Peking University. These findings suggest that PT-symmetric devices could serve as a versatile platform for generating and manipulating diverse quantum resources, with broad implications for advancing quantum information technologies.