Breakthrough Raman-Based Quantum Memory Achieves Near-Perfect Efficiency and Fidelity
Introduction — A New Milestone in Quantum Information Science
In recent decades, quantum physicists and engineers have devised a host of technologies that exploit quantum mechanics to extend the limits of classical information science. Among these innovations, quantum memories have emerged as particularly promising tools for storing and retrieving quantum information carried by light or other media.
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For quantum technologies to be practical, quantum memory must offer both high efficiency and high fidelity. This means retaining and retrieving more than 90% of the incoming quantum information while ensuring the recovered state remains almost identical to the original. Yet many earlier designs for high-performance quantum memories introduced unwanted random fluctuations, creating noise that undermined fidelity.
Major Quantum Memory Breakthrough Reported
A Research team led by Professor Weiping Zhang of Shangai Jiao Tong University and Professor Liqing Chen of East China Normal University has now unveiled a fresh method for controlling atom-light interactions during storage. Reported in Physical Review Letters, their Raman-based quantum memory achieves 94.6% efficiency, extremely low noise and an impressive 98.91% fidelity.
"Quantum memory with almost perfect efficiency and fidelity is essential for quantum information processing," Zhang told publisher. "Reaching this level of performance has long been a major challenge for the field, driving years of research and ultimately motivating this study. Our main goals were to uncover the underlying physics and establish practical methods for achieving truly ideal quantum memory."
A Promising Mathematically Guided Technique
Far-Off-Resonant Raman Scheme
The quantum memory created by Zhang and his team relies on a form of atom-light interaction known as a far-off-resonant Raman scheme. Alongside enabling quantum storage, this approach provides a significant broadband advantage, allowing optical signals to be stored far more rapidly than in many other methods.
Hankel Transform-Based Adaptive Optimization
In their study, the researchers presented a highly accurate and resilient technique that can adaptively optimize a quantum memory until it reaches what they describe as "perfection." The method is rooted in atom-light spatiotemporal mapping, mathematically expressed through the Hankel transform.
"Essentially, this is the first time the physical mechanism behind atom-light mapping in quantum memory has been revealed," Zhang said. "In practical terms, it represents a breakthrough, offering a new and promising route toward achieving benchmark-level quantum memory."
Breaking the Limits of Earlier Quantum Memories
Researchers have now applied their newly formulated mathematical method to a Raman-based quantum memory that uses warm rubidium-87 (⁸⁷Rb) vapour. This strategy successfully overcomes the long-standing "efficiency-fidelity trade-off" that has hindered the creation of truly 'perfect' quantum memories.
The team's latest achievement could pave the way for quantum memories with far superior performance. In time, such devices may enable significant advances across a range of quantum technologies, from long-haul quantum communications to quantum computing and distributed quantum sensing.
Future Directions Toward Quantum Networks
"Looking ahead, our research ambitions include exploring fresh physics-driven principles and incorporating the memory into quantum repeaters for fault-tolerant quantum computing architectures and quantum networks," Zhang noted.
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