India News | Quantum Entanglement Leveraged to Enhance Sensors' Performance

New Delhi, Apr 21 (PTI) Quantum entanglement has been shown to significantly improve the precision of sensors that can be used for navigation without GPS, according to a new study.

The researchers at the University of Arizona, US, where the experiments were performed, said that entanglement can be exploited to improve both measurement sensitivity and the time taken to make the measurement.

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Their study published in the journal Nature Photonics describes how entanglement improves optomechanical sensors, which are usually used to detect an external physical quantity such as magnetic fields.

Optomechanical sensors measure forces that disturb a mechanical sensing device that moves in response. That motion is then measured with light waves.

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Optomechanical sensors can also function as accelerometers, the researchers said, which can be used for inertial navigation on a planet that doesn't have GPS satellites or within a building as a person navigates different floors.

The researchers say that quantum entanglement could make optomechanical sensors more accurate than inertial sensors currently in use.

They say that it could also enable optomechanical sensors to look for very subtle forces, such as identifying the presence of dark matter, or invisible matter believed to account for five times more of the mass in the universe than what we can sense with light.

In this experiment, the sensors were membranes, which acted like drum heads that vibrate after experiencing a push.

To enable high accuracy in miniaturised optomechanical sensors, Zheshen Zhang, associate professor of electrical and computer engineering at the University of Michigan and co-corresponding author of the study, and his team explored quantum entanglement.

Rather than splitting the light once so that it bounced off a sensor and a mirror, they split each beam a second time so that the light bounced off two sensors and two mirrors.

Along with improving accuracy, as the membranes should be vibrating in sync with each other, entanglement was found to add an extra level of coordination.

Zhang's group created the entanglement by "squeezing" the laser light.

"Squeezing redistributes the uncertainty (of knowing a photon's position and momentum), so that the squeezed component is known more precisely, and the anti-squeezed component carries more of the uncertainty. We squeezed the phase because that is what we needed to know for our measurement," said Yi Xia, a recent PhD graduate from Zhang's lab at the University of Arizona and co-corresponding author of the paper.

In squeezed light, the photons are more closely related to one another. Zhang contrasted what happens when the photons go through a beam splitter with cars coming to a fork in the freeway.

"You have three cars going one way and three cars going the other way. But in quantum superposition, each car goes both ways. Now the cars on the left are entangled with the cars on the right," he said.

Because the fluctuations in the two entangled beams are linked, the uncertainties in their phase measurements are correlated.

As a result, with some mathematical wizardry, the team was able to get measurements that are 40 per cent more precise than with two unentangled beams, and they can do it 60 per cent faster.

Further, the precision and speed is expected to rise in proportion to the number of sensors.

(The above story is verified and authored by Press Trust of India (PTI) staff. PTI, India’s premier news agency, employs more than 400 journalists and 500 stringers to cover almost every district and small town in India.. The views appearing in the above post do not reflect the opinions of LatestLY)