Distributed quantum sensor networks

The overarching goal of quantum information science and its enabled emerging quantum
technologies is to demonstrate capabilities beyond what is allowed by their classical counterparts. Sensing is an arena that quantum technologies can achieve advantages over classical sensing
technologies for practical applications in the near term. Quantum metrology studies the
use of nonclassical resources to enhance the performance of measurements for a variety of sensing applications.

High-precision distributed sensing using an entangled quantum network

Quantum-enhanced metrology has been an active area of research for several years now due to its many possible applications, ranging from atomic clocks to biological imaging.

Recent theoretical works proposed distributed quantum sensing (DQS) protocols that enable multiple sensors to leverage their shared entangled states to boost the performance of probing global properties of an interrogated object. Since a multitude of real-world applications rest upon a network or an array of sensors that work collectively to undertake sensing tasks, DQS significantly broadens the applicable scope of quantum metrology and opens a new route for achieving a quantum advantage with near-term quantum hardware.

Inspired by these studies, researchers at the Technical University of Denmark and the University of Copenhagen have recently carried out an experiment investigating the advantages of using an entangled quantum network to sense an averaged phase shift among multiple distributed nodes. Their paper, published in Nature Physics, introduces a series of techniques that could help to collect more precise measurements in a variety of areas.

“Recent studies showed that having non-classical correlations between probes addressing different samples could lead to a gain compared to having non-correlated probes,” Johannes Borregaard, the researcher who initiated the project, told Phys.org. “This inspired us to investigate whether such advantages could be demonstrated already using present technology.”

In their study, Borregaard and his colleagues focused on squeezed light and homodyne detection, which are now established sensing techniques. The overall goal of the experiment was to measure a global property of multiple spatially separated objects and investigate whether probing these objects simultaneously with entangled light led to more precise results than probing them individually. The researchers found that the use of a quantum network to probe the objects simultaneously enabled phase sensing with far higher precision than that attainable when examining probes individually.

Quntao Zhuang, an assistant professor in the Department of Electrical and Computer Engineering and the James C. Wyant College of Optical Sciences, received a 2020 Young Faculty Award from the U.S. Defense Advanced Research Projects Agency, or DARPA.

Zhuang received the award based on his research proposal, “Distributed Quantum Sensor Networks Enhanced by Quantum Error Correction.” Sensor networks are used in applications including GPS navigation, astronomy observation and biomedical imaging — and quantum sensor networks have the potential to be orders of magnitude more precise than their classical counterparts. However, quantum sensor networks are powered by entangled sensors, and the state of entanglement is so fragile and sensitive that it can collapse in the presence of even minimal interference. Zhuang’s project will focus on improving the ability of quantum sensors to perform in the face of noise and other error-causing imperfections.