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Quantum sensing promises to revolutionise several areas for the military, from providing highly accurate positioning data to detecting submarines in the world’s oceans. “Quantum sensing uses some nonintuitive properties of nature to measure things like time, magnetic fields, gravity, or acceleration,” explains Paul Kunz, a scientist at the US Army Research Laboratory. “For instance, a grandfather clock might use an oscillating pendulum to measure time, but small particles like cesium atoms have electrons that can be coaxed to oscillate at well-defined frequencies.”
Systems like GPS, Russia’s GLONASS, China’s BeiDou, and Europe’s Galileo systems are Global Satellite Navigation Systems (GNSS) that provides real-time positioning, navigation and timing (PNT) data. The system provides critical navigation capabilities to military systems including UAVs, soldiers in the dark or in unfamiliar territory, missile and projectile guidance, target tracking, precision munitions, search and rescue, and to coordinate troop and supply movement.
However, in many environments in which military operates (inside buildings, in urban canyons, under dense foliage, underwater, and underground) have limited or no GPS access hence cannot provide continuous and accurate services due to occlusion of signals.. Similarly, GPS signals can be significantly degraded or unavailable during solar storms. GPS and GNSS signals are easily disrupted by unintentional interference from radio transmitters. GPS and GNSS signals are extremely weak, cannot penetrate buildings and can easily be jammed.In addition, radio signals can be eavesdropped or even rewritten, which also causes GPS security to be challenged. Civilian GPS and GNSS signals are not encrypted and can easily be spoofed. Militaries are investigating methods to provide GPS-independent PNT to the Soldier to increase mobility, communications, and enable advanced attack for any mission duration
In this case, a quantum technology-based navigation system may be the solution. The Quantum Positioning System (QPS) was first proposed in 2001 by Dr. Giovanniti of the Massachusetts Institute of Technology (MIT) in the journal Nature. It is proved by calculation that the quantum entanglement and compression characteristics can further improve the positioning accuracy. By means of the preparation of quantum entangled state and its transmission technology, QPS no longer uses electromagnetic waves, which can not only break through the limits of traditional positioning accuracy, but also provide good protection in terms of confidentiality and anti-interference ability. Its energy consumption is much smaller than that of traditional ones. The system may bring fundamental improvements to the miniaturization, continuous working hours and stealth performance of the device.
During testimony Wednesday before the House Armed Services Committee, Michael D. Griffin, undersecretary of defense for research and engineering, said quantum computing and quantum communication are not beyond the boundaries of physics, but are still long-term prospects for use in the department. Instead, Griffin said, the department is focused on quantum technology that’s going to be of use to the force in the shorter term.
“First and foremost [are] quantum clocks to give us timekeeping, precision, synchronized timekeeping and precision [that are] two, or possibly even three, orders of magnitude better than we have today,” Griffin told lawmakers. “That’s critically important for maintaining communications in a GPS-denied environment where we might have to fight a war.” Quantum sensors for inertial navigation or navigation by other means, as well as quantum magnetometers to improve navigation information, are also critical technologies, Griffin said. “These are the things that we will see in the next few years and where we are focusing a substantial amount of our effort,” Griffin said. In the department’s fiscal year 2021 budget request, Griffin said, DOD has asked for $23 million to further the development of an enhanced-stability atomic clock that will provide a constant connection to sensor networks and encrypted communication channels that support DOD’s most critical missions.
Pentagon is looking for a quantum space sensor
The Defense Innovation Unit — the organization within the DoD charged with leveraging commercial technologies for military use — is seeking a compact, high-performance sensor that can use quantum technology to provide precise inertial measurements in deep space. The quantum sensor could also be used in non-space environments where GPS signals are degraded and denied. According to DIU Program Manager George Sondecker, quantum sensors are an emerging technology, and a “primary objective of this effort is to mature the technology readiness of commercial sensors for reliable operations.” DIU is not developing the quantum sensor for any space vehicle in particular.
“No specific platform has been identified. The sensor is intended to be applicable across a broad range of platforms for operating in environments where GPS may be unavailable or for enhancing operations where GPS is available,” Sondecker wrote in an emailed statement. “DIU is partnered with a number of stakeholders across the DoD to develop the Quantum Space Sensor identified in this solicitation.”
Participants will need to deliver their flight-ready prototypes within 24 months. Specifically, DIU wants sensors with error rates better than 100 meters per hour in deep space or 30 meters per hour for terrestrial applications while being no bigger than 0.1 cubic meters.
Quantum Positioning System (QPS)
QPS can be divided into two categories: quantum active navigation system and quantum passive navigation system. The quantum active navigation system adopts the method of transmitting and receiving quantum signals. The positioning process usually uses satellite as the signal source. The quantum passive navigation uses quantum sensor device to locate, does not need external signals, and is usually positioned by detecting acceleration. Active navigation systems typically use satellites as the source of ranging, and quantum active navigation is no exception . In 2004, Dr. Bahder of the US Army Research Laboratory proposed an interferometric quantum positioning system.
The system uses a system structure similar to that of traditional satellite navigation. One of the schemes consists of three baselines, each of which contains two low-orbiting satellites with the Earth’s center as the coordinate origin, and the three baselines form a coordinate system perpendicular to each other. In addition, each baseline includes a semiconductor light source, a delay filter, a beam splitter and two photon detectors. First, the light source respectively emits beams to the two satellites, and after reflection, reaches the beam splitter, and then the splitter respectively transmits the two photon detectors, and by adjusting the delay time, the counting rate of the observed entangled photons is minimized. At this point, it can be known that the two paths have the same propagation time. Finally, by calculating the distance between the satellites and the delay generated by the delay filter, the precise position of the target can be calculated by the mathematical platform.
In addition to satellite-based quantum active navigation systems, quantum passive navigation systems based on inertial navigation will also be an important means of exploring future navigation. In modern applications, inertial passive navigation is often combined with satellite active navigation for better results. In addition, the process of passive navigation does not exchange information with the outside world, which makes the passive navigation system have high credibility and high availability, which makes it a very popular military application, such as nuclear submarines and other important moving targets that need to hide their position.
The quantum navigation utilizes the microscopic quantum characteristics of photons and can even surpass the limit of classical measurement to achieve higher precision. It is an emerging technology with great potential. The rapid development of quantum information technology has promoted the development of quantum device and quantum signal preparation, manipulation and storage related technologies.
Key technologies of quantum active navigation system
Preparation of photon entangled states.
Quantum satellite navigation systems require many entangled photons during the ranging process. At present, there are various methods for preparing entangled states, such as parametric down-conversion effects of nonlinear crystals, ion traps, and atomic-optical cavities. The entangled state is prepared by the Spontaneous Parametric Downconversion (SPDC) method. Use laser pass the nonlinear crystal by the spontaneous parametric downconversion process of laser-pumped nonlinear optical crystals, and the twin photon pairs produced have extremely high entanglement purity.
An ion trap is a device that confines ions in a confined space by an electromagnetic field. The study of the preparation of entangled states by ion traps is mainly to realize the entangled state of two atoms or even multiple atoms in the trapped ion system. This method has two main advantages: First, the ions are trapped in a highly vacuum environment, almost isolated from the “interference” condition, so it has a relatively long decoherence time; the second is the preparation of the initial state and the measurement of quantum states has a very high fidelity phase efficiency, which is beneficial to quantum computing and quantum information processing.
Capture, Tracking and Aiming Systems and Techniques.
Quantum satellite navigation systems also require spatial optical communication and ATP technique (acquisition, tracking and aiming). The basis of ATP technology comes from the techniques of optical positioning, detection and tracking commonly used in satellite laser communication. The tasks of system include the acquisition and highprecision tracking of beacon light transmitted by satellite communication terminals, and the high efficiency and high polarization-preserving reception of on-board quantum signal light. The difficulty of spatial ATP technology lies in two aspects. One is the requirement of high precision. Considering the influence of spatial loss on the bit error rate, the quantum light divergence angle in spatial scale quantum communication is usually close to the optical diffraction limit, so the beam must aligned in micro radians level(µrad); the second is the requirement of high stability, The system is affected by factors such as atmospheric channel loss, satellite platform interference, and space thermal environment. A good ATP system work well in those situations.
Quantum clock synchronization technology.
The quantum clock synchronization is derived from the quantum entanglement of pairs of quantum (photons or atoms). In quantum active navigation systems, positioning and clock synchronization are two relatively independent processes. Through the second-order quantum coherence, the clock difference between the user clock and the system clock located near the origin of the coordinate system is accurately measured, and the user clock is synchronized to the system clock. The synchronization process of the satellite-based QPS does not require the distance between the user clock and the system clock. In addition, since the two-photon coincidence count measurement of the HOM interferometer only requires the clock to remain stable for a short measurement period, clock synchronization has only
short-term stability requirements for the user clock and the on-board clock, and there is no long-term stability requirement. However, the system clock located near the origin of the coordinate system should have good long-term stability to maintain accurate system time for a long time.
Quantum passive navigation system and its key technologies
Quantum passive navigation system
The quantum passive navigation system is an inertial navigation system. Like the traditional inertial navigation system, its ranging and timing implementation does not depend on the real-time reception of spatial satellite signals. The state adjustment and positioning are performed by inertial devices. Therefore, the principle of the quantum inertial navigation system is to accurately locate the atomic inertia parameters after the atoms are disturbed. The quantum inertial navigation system has the same structure as the conventional inertial navigation. It composed of four parts: three-dimensional atomic gyro, accelerometer, atomic clock and signal processing module. Some structures also include spatiotemporal information transceiver module and attitude control module. Among them, atomic gyro, accelerometer and atomic clock are the core modules in quantum passive navigation system, and their performance directly affects the system positioning performance.
Atomic Gyroscope.
According to different working principles, atomic gyros can be divided into atomic interference gyro and atomic spin gyro. The atomic interference gyroscope is based on the atomic Sagnac effect. The cold atomic mass forms a cold atomic beam along the same parabolic trajectory in the opposite direction. Under Raman laser stimulation, an interference loop is formed due to the double loop atomic interference. The half of the phase shift difference is the phase shift caused by the rotation rate, so we can get the rotation rate. The theoretical value of the zero-bias drift of the atomic interference gyroscope is much lower than that of the traditional gyroscope. The theoretical recision can be the 1010 times of optical gyroscope. The atomic spin gyro is using the spin of an alkali metal atom’s Larmor precession to achieve angular velocity sensing. There are currently two mainstream schemes for atomic spin gyros: one is the nuclear magnetic resonance atomic spin gyro (NMRG) using the dual-nuclear method, and the other is the atomic spin gyro operating in the spin-exchangeless relaxation state (SERFG).
Atomic accelerometer.
The discovery of the cold atom interference effect has led to the birth of atomic accelerometers, so its development is usually accompanied by the development of cold atom interference gyroscopes. Quantum accelerometers are several orders of magnitude better than traditional inertial devices. For example, if the position measurement error is less than 1 km after 100 days of sailing on a submarine, the submarine can perform long-term latency without satellite navigation.
Q-CTRL to provide expertise on quantum-enhanced sensing to Advanced Navigation’s ultra-precise, AI-based navigational manufacturing.
Q-CTRL, a startup that applies the principles of control engineering to accelerate the development of quantum technology, announced in July 2020, a global research and technology development partnership with Advanced Navigation, a leader in AI-based navigational hardware. Q-CTRL and Advanced Navigation entered the partnership in early 2020 in support of their collaborative research and development in quantum-enabled sensing. The two organizations will now be conducting joint technical development in support of both the civilian and defense markets focused on quantum-enhanced precision navigation and timing (PNT).
Quantum sensing is considered one of the most promising areas in the global research effort to leverage the exotic properties of quantum physics for real-world benefit. It is expected to revolutionize PNT through an ability to detect very weak accelerations while maintaining accuracy over long times. Quantum-enabled PNT can therefore enable highly precise navigation in commercial and military applications where GPS is unavailable.
Q-CTRL is a pioneer in the field of quantum control engineering which applies the lessons of classical control engineering to stabilize quantum systems against disturbances in their environment, a critical component in bringing quantum sensing to market. The firm is a trusted provider of quantum control solutions across all applications of quantum technology, and has a growing practice in quantum sensing for aerospace and defense.
Advanced Navigation builds ultra-precise, AI-based navigational technologies and robotics for sea, air, land and space across commercial and defense domains. Their team has specialized expertise across a broad range of fields including optical and MEMS based inertial sensors, GNSS, inertial navigation, RF technologies, acoustics, robotics, AI and algorithms. “We are excited to enter into a partnership with Q-CTRL who has the world’s largest and most capable specialist team of quantum control engineers,” said Chris Shaw co-CEO and co-founder of Advanced Navigation. “Combining our expertise and manufacturing capability in precision navigation technologies, along with Q-CTRL’s expertise in the design and operation of advanced quantum hardware, will allow us to bring next-generation quantum PNT solutions to market.”
“The team at Q-CTRL is thrilled to have entered a commercial engagement with Advanced Navigation,” said Q-CTRL CEO and founder Prof. Michael J. Biercuk. “Our shared affinity for the role of control and machine learning in improving hardware performance make for a perfect match, and we’re exceptionally excited to deploy our team’s expertise in quantum sensing for production quantum-enhanced PNT systems.” The Institute for Defense Analysis has highlighted precision navigation in GPS-denied environments as a key application for quantum technology, with the potential to support maritime systems, UAVs, and aircraft. With improvements in system size and performance, IDA forecasts a quantum PNT market exceeding $200 million annually by 2024.
Q-CTRL and Advanced Navigation hope to dramatically expand this opportunity through the development of ultra-high-performance software-enabled hybrid quantum PNT systems for autonomous vehicles, defense, and space applications.
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