Using quantum entanglement as a GPS, precise positioning can be achieved even in areas with no signal

Quantum entanglement refers to a special coupling phenomenon that occurs between particles. In the entangled state, we cannot describe the properties of each particle individually, but can only describe the properties of the overall system. This influence does not disappear with the change of distance, even if the particles are separated by the entire universe.

A new study shows that using quantum entanglement mechanisms, sensors can be more accurate and faster at detecting motion. Scientists believe the findings could help develop navigation systems that do not rely on GPS.

In a new study submitted in "Nature Photonics" by the University of Arizona and other institutions, researchers conducted experiments on optomechanical sensors, which use light beams to interfere with to respond. These sensors act as accelerometers, which smartphones can use to detect motion. On the other hand, accelerometers can also be used in inertial navigation systems in areas with poor GPS signals, such as underground, underwater, inside buildings, remote areas, and places where radio signals are interfered with.

The paper "Entanglement-enhanced optomechanical sensing":

##Paper link: https://www.nature.com/articles/s41566-023-01178-0

In order to improve photomechanical sensing To improve performance, researchers have tried using entanglement, which Einstein called "spooky action at a distance." Entangled particles are essentially in sync, no matter how far apart they are.

The researchers hope to have a prototype entangled accelerometer chip within the next two years.

Although quantum entanglement ignores distance, it is also extremely susceptible to external interference. Quantum sensors exploit this sensitivity to help detect the slightest disturbance in the surrounding environment.

"Our previous research on quantum-enhanced optomechanical sensing has mainly focused on improving the sensitivity of a single sensor," said lead author of the study, Quantum Physics at the University of Arizona, Tucson. Scientist Yi Xia said. "However, recent theoretical and experimental studies have shown that entanglement can greatly improve the sensitivity between multiple sensors, an approach known as distributed quantum sensing."

Optomechanics The sensor's mechanism relies on two synchronized laser beams. A beam of light is reflected by a component called an oscillator, and any movement of the oscillator changes the distance the light travels on its way to the detector. Any such difference in distance traveled becomes apparent when the second beam overlaps the first. If the sensor is stationary, the two beams are perfectly aligned; if the sensor is moving, the overlapping light waves create an interference pattern that reveals the magnitude and speed of the sensor's movement.

In the new study, the sensor from Dal Wilson's group at the University of Arizona uses a membrane as an oscillator, which works very well. Like a drum head that vibrates after being struck.

Here, instead of shining one beam at one oscillator, the researchers split an infrared laser beam into two entangled beams, which reflected from the two oscillators to the two on a detector. This entangled nature of light essentially allows two sensors to analyze a single beam of light, working together to increase speed and accuracy.

"We can use entanglement to enhance the force-sensing performance of multiple optomechanical sensors," said the study's lead author Zheshen Zhang, a quantum physicist at the University of Michigan in Ann Arbor. .

In addition, in order to improve the accuracy of the device, the researchers used so-called "compressed light". Squeezing light takes advantage of a key principle of quantum physics: Heisenberg's Uncertainty Principle, which states that when a particle's position is determined, its momentum is completely uncertain; if its momentum is determined, its position is completely uncertain. Not sure at all. Squeezed light exploits this trade-off to “squeeze” or reduce the uncertainty in the measurement of a given variable — in this case, the phase of the waves that make up the laser beam — while increasing the uncertainty in the measurement of another variable, but the study Personnel can be ignored.

"We are one of the few teams that can create a compressed light source and are currently exploring it as the basis for the next generation of precision measurement technology," said Zheshen Zhang.

All in all, the scientists were able to collect measurements that were 40% more precise and 60% faster than using two unentangled beams. Furthermore, they say the accuracy and speed of this method are expected to increase as the number of sensors increases.

"These findings mean we can further improve the performance of ultra-precision force sensing to unprecedented levels," said Zheshen Zhang.

Researchers say that improving optomechanical sensors could not only lead to better inertial navigation systems, but also help detect mysterious phenomena such as dark matter and gravitational waves. Dark matter is an invisible substance thought to make up five-sixths of all matter in the universe, and detecting its possible gravitational effects can help scientists figure out its properties. Gravitational waves are ripples in the fabric of space-time that can help reveal mysteries from black holes to the Big Bang.

Next, the scientists plan to miniaturize their system. It is already possible to place compressed light sources on chips that are only half a centimeter wide. Within the next year or two we can expect to have prototype chips that include squeezed light sources, beam splitters, waveguides and inertial sensors. "This will make this technology more practical, more affordable, and more accessible," said Zheshen Zhang.

In addition, the research team is currently working with Honeywell, Jet Propulsion Laboratory, NIST and several other universities to develop a chip-scale quantum enhanced inertial measurement unit. "Our vision is to deploy such integrated sensors in autonomous vehicles and spacecraft to achieve precise navigation without GPS signals," said Zheshen Zhang.

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