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US patents Quantum Entanglement based techniques for detection of stealthy Russian and Chinese submarines even under arctic

The US Government has now tuned to Quantum sensors to detect stealthy Russian and Chinese submarines. Quantum sensors are measuring device that takes advantage of quantum correlations, such as states in a quantum superposition or entanglement, for better sensitivity and resolution than can be obtained by classical systems. Quantum sensors are just becoming commercially available.

Russia has been devloping super quiet submarines like new lada-class diesel electric submarines. “The stealth capabilities of Russia’s new Lada-class diesel-electric submarines far exceed those of their predecessors, Admiraty Shipyard’s CEO Alexander Buzakov told the Russian press. “According to Buzakov, the new vessels are even stealthier than Russian Kilo-class submarines, thought to be one of the quietest diesel-electric submarine classes in the world and dubbed “black holes” for their ability to “disappear” from sonars. “The new submarines are able to maintain such a low profile thanks to a clever implementation of a next-generation anti-reflective acoustic coating and a new improved hydro-acoustic system, Buzakov said

DARPA considers ultra-quiet as well as highly lethal submarines as an asymmetric threat and in response has launched number of programs like the Distributed Agile Submarine Hunting (DASH) program that intends to reverse the asymmetric advantage of this threat through the development of advanced standoff sensing from unmanned systems.

US Navy now plans to employ quantum entanglement to detect invisible submarines. Entanglement is phenomenon in which the physical states of two or more objects such as atoms, photons or ions become so inextricably connected that the state of one particle can instantly influence the state of the other—no matter how far apart they are. Today, entanglement is actively being explored as a resource for future technologies including quantum computers, quantum communication networks and high-precision quantum sensors.


Quantum Entanglement can provide capability to detect stealthy objects

A recent patent from US Navy reveals details of their awesome quantum photonic imaging device to detect of underwater objects. The patented invention would provide complete stealth during operation.

The invention uses quantum entanglement as a means to achieve detection of reflected radiation at levels that are below the noise level. In a way, this is similar to how CDMA works by spreading information under the noise floor making it virtually indistinguishable from noise until it’s correlated with the correct code sequence.

Just like that, the patented device generates a pair of entangled photons one of which (call it “probe photon”) is transmitted towards a target. The probe photon is reflected by the target. The reflected radiation which includes noise is then correlated with the other photon of the pair. Only when the reflected radiation includes a reflection of the probe photon, the correlation with the other photon is high, which indicates presence of an object. Multiple pairs of entangled photons are used to determine range and geometry of the target object.

The target object can be an Arctic ice canopy, ocean bottom, and another natural or artificial obstacle in the water that can obstruct under-ice passage of the vehicle in Arctic waters. The patented device is particularly useful under Arctic sea-ice canopy, where conventional current underwater navigation systems fail.

Conventional arctic underwater vehicles use an (detection systems employ) active sonar array to avoid an accidental collision with the ice canopy. However, in the case of Arctic military operations, active sonar will give away the position of the submarine.


Entanglement can improve performance of optical sensors

Members of the Optical and Quantum Communications Group at MIT’s Research Laboratory of Electronics have demonstrated that entanglement can also improve the performance of optical sensors, even when it doesn’t survive light’s interaction with the environment.

In the MIT researchers’ system, two beams of light are entangled, and one of them is stored locally—racing through an optical fiber—while the other is projected into the environment. When light from the projected beam—the “probe”—is reflected back, it carries information about the objects it has encountered. But this light is also corrupted by the environmental influences that engineers call “noise.” Recombining it with the locally stored beam helps suppress the noise, recovering the information.

The local beam is useful for noise suppression because its phase is correlated with that of the probe. If you think of light as a wave, with regular crests and troughs, two beams are in phase if their crests and troughs coincide. If the crests of one are aligned with the troughs of the other, their phases are anti-correlated

Quantum mechanics does not allow you to precisely measure the phase of each individual photon, instead, quantum mechanics interprets phase statistically.

When a probe beam interacts with the environment, the noise it accumulates also increases the uncertainty of the ensuing phase measurements. But that’s as true of classical beams as it is of entangled beams. Because entangled beams start out with stronger correlations, even when noise causes them to fall back within classical limits, they still fare better than classical beams do under the same circumstances.

In experiments that compared optical systems that used entangled light and classical light, the researchers found that the entangled-light systems increased the signal-to-noise ratio—a measure of how much information can be recaptured from the reflected probe—by 20 percent. That accorded very well with their theoretical predictions.

But the theory also predicts that improvements in the quality of the optical equipment used in the experiment could double or perhaps even quadruple the signal-to-noise ratio. Since detection error declines exponentially with the signal-to-noise ratio that could translate to a million-fold increase in sensitivity.

“This is a breakthrough,” says Stefano Pirandola, an associate professor of computer science at the University of York in England. “One of the main technical challenges was the experimental realization of a practical receiver for quantum illumination. Shapiro and Wong experimentally implemented a quantum receiver, which is not optimal but is still able to prove the quantum illumination advantage. In particular, they were able to overcome the major problem associated with the loss in the optical storage of the idler beam.”

“This research can potentially lead to the development of a quantum LIDAR which is able to spot almost-invisible objects in a very noisy background,” he adds. “The working mechanism of quantum illumination could in fact be exploited at short-distances as well, for instance to develop non-invasive techniques of quantum sensing with potential applications in biomedicine.”


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