$9M Project Aims to Find the Precision Ceiling of Entangled Quantum Sensor Networks
Quantum sensors already outperform classical devices in sensitivity and accuracy. A five-year, $9 million project now wants to answer a harder question: how much better can they get when connected through quantum entanglement?
The U.S. Office of Naval Research is funding the initiative through a Multidisciplinary University Research Initiative grant, with the University of Michigan leading a six-institution team that includes Princeton, the University of Chicago, the University of Maryland, the University of Arizona, and the University of Southern California.
The precision advantage entanglement promises
Conventional sensor networks improve with the square root of the number of sensors - double the sensors, gain roughly 41 percent more precision. Entanglement, the quantum property that links particles regardless of physical distance, promises a fundamentally different scaling law. According to project leader Zheshen Zhang, associate professor of electrical and computer engineering at Michigan, entangled networks can improve sensitivity with the square of the number of sensors.
"Over the past few years, we discovered that entanglement can allow you to improve the performance of a sensor network in terms of the resolution - so you can actually detect finer details and take measurements faster than a conventional sensor network, with more sensitivity or higher signal-to-noise ratio," Zhang said.
Quantum sensors today are already connected through conventional fiber-optic links. The core research question this project seeks to answer is quantitative: how much additional precision does entangled networking actually deliver above and beyond those conventional connections?
Two experimental testbeds, two distinct physical platforms
The team will build and operate two distinct testbed systems.
The first, led by Jeff Thompson at Princeton, uses Rydberg atoms - atoms whose electrons have absorbed enough energy that their orbits extend far from the nucleus, making them exceptionally sensitive to electric and magnetic fields. When two neighboring Rydberg atoms are hit with simultaneous laser pulses, they enter a quantum superposition where it is indeterminate which atom holds the excited electron. Both atoms then act as sensors and instantly react to any signal picked up by either. The team begins with an array of 25 qubits and plans to scale to several hundred.
The second testbed, led by Zhang at Michigan, uses a vibrating membrane that oscillates in response to light waves. The plan is to upgrade a single sensor to a four-sensor system and cool the assembly to 0.1 Kelvin - one-tenth of a degree above absolute zero - so cold that quantum fluctuations dominate over thermal noise. These sensors will be linked with entangled light beams.
Maintaining entanglement against environmental noise
A central technical challenge is keeping entanglement intact. Thermal vibrations, stray electromagnetic fields, and mechanical disturbances constantly threaten to break the quantum bonds between linked particles. The team will develop error suppression and correction techniques using the testbeds as proving grounds, work that could contribute to the eventual architecture of a broader quantum internet.
If successful, the results could improve atomic clocks used in telecommunications and financial networks, inertial navigation systems that operate without GPS, and detectors for magnetic fields and radiofrequency radiation in medical and defense applications. Whether entanglement's theoretical precision advantages survive contact with real hardware noise - and at what scale they become practically useful - are exactly the open questions the project intends to answer.