The Genius Behind the Quantum Navigation Breakthrough

Source: The Genius Behind the Quantum Navigation Breakthrough, Dr Ben Miles, 20:47, uploaded 2024-09-12, category Mathematics, playlist index 562.

Dr Ben Miles begins with a flight between Helsinki and Tartu whose navigation display places the aircraft thousands of miles away, above the Pacific. The story sounds like a lost-aircraft thriller until the cause comes into view: GPS interference around the Baltic, which the video links to Russian activity near St Petersburg. A global map of GPS threats shows a high-failure zone along the Helsinki–Tartu route, and another dead zone appears west of San Antonio. Miles also points to footage of drone shows in which many aircraft fall from the sky at once, then asks what remains when the navigation system used by military and civilian aircraft can be jammed or spoofed.

GPS failure and the need for inertial navigation

GPS works through trilateration. Satellites broadcast their positions and clock times, and a receiver measures how long each signal took to arrive. Multiplying that time difference by the speed of light gives the receiver a distance from each satellite. Three or more overlapping distance rings settle on a position. The system depends on an outside radio signal, which gives an attacker two useful points of entry. A jammer blocks the signal. A spoofer supplies a false signal that makes the receiver calculate the wrong position. Buildings, mountains and underground railways can also block the signal without any hostile actor.

When GPS disappears, a vehicle can use dead reckoning. Sailors already used the basic method in the seventeenth century. They fixed their starting point, followed a compass bearing and estimated distance from time and speed. A log thrown overboard dragged a rope with knots tied every 47 feet, which gave sailors a rough speed reading. The unit knot still carries that history. Aircraft later measured acceleration instead of relying on a mostly constant speed. An inertial measurement unit, or IMU, integrates acceleration into velocity and velocity into position while rotation sensors track changes in orientation. The video explains this with a passenger in the back of a car or with Einstein being pushed against the wall of a rocket as it accelerates.

The attraction is independence from an external reference. An inertial system needs its starting position and the physical motion measured by its sensors, so a radio attacker has less to work with. The method has a serious weakness of its own. Sensor drift and noise accumulate each time the system integrates forward. A position that begins with a small error can become useless after hours or days. A submarine makes the problem clear because GPS signals cannot reach it underwater, while a small error in its estimated motion can place it far from a narrow channel. Infleqtion’s proposal is a quantum inertial sensor that uses the physical behaviour of ultra-cold atoms to reduce that drift.

Atoms cold enough to measure motion

The Oxford team starts by cooling and trapping atoms with magnetic fields and light. The first step uses Doppler cooling. A photon briefly interacts with an atom and is then re-emitted in a random direction. When an atom moves towards a slightly red-shifted laser beam, the Doppler effect moves the light closer to the frequency that the atom absorbs. The atom takes in the photon, receives a recoil against its motion and loses a small amount of speed. Repeating the interaction millions of times slows the cloud almost to a stop.

Six laser beams push along three axes. A magnetic field supplies the restoring force that holds the cold atoms near the centre of the vacuum chamber, producing a magneto-optical trap. Miles cannot see the infrared beams with the main camera or his eyes, so he holds a phone in front of the camera and the trapped cloud appears as a red dot. An infrared camera shows the cloud assembling when the trap is on, then expanding through the chamber when the confinement disappears. The image is a blurred mark because the experiment turns a cloud of invisible atoms into a visible shadow.

The apparatus moves the atoms through several traps. A two-dimensional magneto-optical trap feeds atoms through a push beam into an upper chamber, where three-dimensional cooling continues. Magnetic fields and currents in a chip then load the atoms into a tighter trap. The target is a Bose–Einstein condensate. As the atoms cool, their momentum falls and their matter wavelengths grow. Once those wavelengths overlap, bosons such as rubidium-87 or sodium-23 can occupy the same lowest-energy state. The collection begins to behave like one coherent super-atom, with quantum effects visible at a scale that a camera can record. The team wants that coherence because it makes matter-wave interference sensitive to acceleration.

A condensate as a matter-wave interferometer

Interferometry measures the pattern produced when waves travel apart and meet again. LIGO uses interference between light waves to detect gravitational waves. Infleqtion applies the same broad idea to matter. A coherent laser pulse splits the condensate into two wave packets inside a dipole trap. The packets move in opposite directions, then another pulse reverses them so they meet again. Their final phase records the acceleration that affected them during the sequence.

The measurement reads out the cloud as three populations in different momentum states. A camera takes an absorption image after the atoms fall briefly, and the relative density of the three blobs reveals the phase accumulated by the condensate. The image destroys the condensate, so the experiment starts the cooling cycle again after each measurement. The team says it can produce one image roughly every second. A ship or aircraft moving up, down, sideways or forwards changes the two matter waves by a small amount, leaving an interference signal that the sensor can turn into acceleration and rotation.

From a laboratory to an aircraft

The individual steps are hard in a laboratory, where optical tables float and the magnetic and light environments stay carefully shielded. The more demanding test came in May, when the team flew the apparatus on a research aircraft. The video shows the aircraft banking while the system produces a Bose–Einstein condensate. The experiment alternates between imaging the condensate directly and splitting it for the first stage of interferometry. After the atoms fall, absorption imaging measures their shadow and the three resulting populations allow the team to calculate the phase associated with the aircraft’s acceleration or rotation.

The demonstration matters because the aircraft keeps moving while the condensate forms and is split. The engines shake the apparatus, the weather radar sends out strong electromagnetic signals and air-traffic systems fill the surrounding environment with more radio activity. Mechanical and electromagnetic noise limit quantum devices in the laboratory, and the aircraft forces the same problem into the open. The video presents the stable in-flight condensate as evidence that this particular experiment has moved beyond a static laboratory setup.

Development path and other measurements

The team describes the aircraft experiment as an early point on a longer development path. It still needs deployed trials and comparisons with existing inertial sensors. The researchers expect the first products to occupy a rack in a data centre, ship or aircraft. Over the following years they hope to ruggedise and miniaturise the lasers, optics and vapour cells with photonic integrated circuits that print the components onto silicon. Their stated long-term aim is a sensor small enough to hold in one hand.

The same sensitivity to acceleration gives the atoms a sensitivity to gravity. A precise gravity map could reveal mineral deposits, tunnels and geological formations below the ground. The video also names navigation for autonomous vehicles between tall buildings and navigation in space as possible later uses. The first practical target remains aircraft, at a time when Miles says an average of 900 flights a day encounter GPS spoofing. That figure appears in the video without a named source or supporting data, so it remains a claim made by the production rather than an independently checked statistic here.

Limits of the demonstration

The video documents a research prototype and an aircraft test. It does not give a navigation-error figure, a drift comparison against a named commercial IMU, or the results of a full deployed trial. “Unhackable” describes the absence of an external positioning signal in the inertial method; physical access to the device, calibration error and the remaining sensor noise still matter. The film establishes that a Bose–Einstein-condensate interferometer can operate during a flight, while the size, cost, accuracy and operational reliability of a finished navigation product remain open engineering questions.

Further reading / references

• Infleqtion, the company whose Oxford team and quantum-navigation work appear in the video.