Quantum enhanced GPS
Global Positioning System
The Global Positioning System (GPS) is a global satellite system that enables us to define a GPS receiver’s location anywhere on Earth. All it needs is line of sight with 4 of the 31 GPS satellites that are circling the Earth. Developed and operated by the US Government, it became available for civilian use in the 1980s. Like with many new technologies, the scientists and engineers who developed the system could never have imagined what it would be used for 30 years later. Today, many businesses rely on GPS for their operations. It is used to navigate vehicles, to map forests and agricultural lands, to locate people in need of assistance, to track movements of wildlife, packages, containers and vehicles, and countless other applications. Location-based services have become part of everyday life. We use our smartphones to determine where we are and how to get to our target destination, to measure speed and distance when we go running, to check the whereabouts of our pets, or to capture creatures in Pokémon Go.
But GPS isn’t perfect yet. It is vulnerable to cyber-attacks, and doesn’t work flawlessly in urban areas. Moreover, its accuracy can be influenced by the US government, which is one of the reasons why the European Union is implementing the non-military Galileo global navigation system. The accuracy of this system will be approximately 1 meter, but quantum technology can improve this even further.
More accurate GPS
GPS relies on atomic clocks. By measuring the time it takes to receive a time signature from a specific satellite, and doing this for four different GPS satellites, a GPS receiver can determine where it is on Earth. The US government commits to broadcasting the GPS signal in space with a global average user range error (URE) of less than 7.8 meters with 95% probability. Although the actual performance of the GPS system is better, most GPS-defined locations are still off by a few meters. This is partly caused by small variations that occur in atomic clocks on board of GPS satellites. A signal travelling at the speed of light takes about 70 milliseconds to reach you, so you can imagine that the slightest deviation between clocks can result in a location measurement that is off by meters. If clocks on board of satellites did not regularly synchronize, GPS performance would rapidly deteriorate and would be useless in a matter of weeks.
In the future it will be possible to use quantum communication technology to synchronize more accurately, transferring time information directly between the quantum memories in GPS satellites. The result? Pinpointing your location with much higher accuracy, theoretically up to 15 centimeters.
GPS is so ubiquitous that failure of the system will have a huge impact. Unfortunately, there have been events of hacks and spoofs in the past. Besides the economic impact, these also create potentially dangerous situations, e.g. through malfunctioning air traffic control. With spoofing, the receiver gets false data, resulting into a false location and/or a false time. There have been recent events where GPS signals told ships they were on land, while they were actually at sea.
By using entanglement and quantum communication, we can be sure the time signature is authentic, improving safety for all.
A quantum alternative to GPS
GPS doesn’t work if you’re indoors or if you do not have satellites in sight: in between tall buildings, you will have a hard time getting a reliable GPS signal. Quantum technology may solve all this.
A special type of quantum sensors – quantum accelerometers and quantum gyroscopes – can be combined into quantum autonomous navigation systems. Such a system may enable location tracking without the aid of GPS satellites. Classical autonomous inertial navigation systems are already used on ships, aircraft, cruise missiles, and even in smartphones. They detect acceleration, movement and orientation, but they are too inaccurate to be a sole source of data for navigation. Quantum autonomous navigation systems, on the other hand, are extremely accurate. Using a starting point as a fixed reference, data from a quantum navigation system will give us all the information we need to accurately determine where we are.
Benefits of quantum navigation and positioning systems over GPS are improved accuracy, no reliance on satellite, indoor usage, less vulnerability to hacking and no sensitivity to electromagnetic pulse attacks (which would happen for example after an atomic attack, most likely causing GPS systems to stop working).
Today, the equipment needed for quantum inertial navigation systems is large, complex and costly, but this will improve over time. First, we expect commercial availability of quantum enhanced navigation equipment, combining GPS and quantum sensors, to navigate large vehicles like cargo ships and trains. As the technology further develops, devices will get smaller and will eventually become suited for smaller vehicles and other applications. Maybe one day we will even have a quantum autonomous positioning system in our smartphones.