Quantum technology is founded on quantum mechanics, but the quantum state is limited by its unique properties, such as decoherence and entanglement. However, scientists have figured out a way to exploit these properties in developing ultra-sensitive measurement devices, which are currently finding their way into orbit.
Quantum devices are increasingly being installed in orbit aboard satellites. An example is the SpooQy-1 built at the Centre for Quantum Technologies (CQT) at the National University of Singapore. The satellite was fitted with SPEQS-2, a device for producing pairs of polarization-correlated photons. SpooQy-1 demonstrated quantum entanglement in orbit, paving the way for quantum Internet.
We rely on satellites for global communications and GPS services. Introducing quantum technology into these areas will advance what has already been achieved in space-based technology. The following are some key space-based quantum initiatives.
Quantum sensing is an emerging technology that allows us to measure and manipulate the world at the atomic level. It leverages quantum entanglement, quantum interference, and quantum state squeezing to sense motion and electric and magnetic fields.
Quantum sensors can detect images beneath Earth, ranging from transit tunnels, sewers, and water pipelines to ancient ruins and mines. More accurate sensing can significantly benefit civil engineering, particularly around nuclear power plants, high-speed rail, etc.
Such space-based sensors may also monitor minute gravity changes and tectonic movements, which can predict avalanches, earthquakes, volcanic eruptions, and tsunamis.
Time And Frequency Transfer
Many modern conveniences, such as telecom networks, rely on GPS clocks to keep cell towers synced so that calls may be transmitted between them. Clocks are used in many electric power systems to fine-tune current flow.
But depending on the existing atomic clocks for timestamping, as GPS satellites now do, is becoming increasingly difficult. GPS navigation is now precise to around three meters (about ten feet), which makes it challenging to use for autonomous driving, for example.
To improve on existing time keeping and associated applications, there’s a need for a more accurate clock and precise time transmission and sharing.
Quantum technologies have the potential to increase time precision by orders of magnitude, and using them in space can expand their reach. Increased time precision will improve present communications and geolocation services while enabling new applications.
Quantum Key Distribution (QKD) and Secure Communication Networks
Quantum Key Distribution (QKD) is a cryptographic technique that enables two parties to generate a shared random secret key through the use of quantum mechanics. The method is thought to be unhackable since any effort to eavesdrop destroys the keys.
Current encryption methods, such as the RSA public-key cryptosystem, rely on the difficulty of solving mathematical problems, whereas QKD relies on physical processes.
QKD is possible because of the “no-cloning” theorem in quantum physics, which argues that producing identical clones of an unknown quantum state is impossible. This prevents hackers from just replicating the quantum-encoded data. Another quantum feature called the “observer effect” causes quantum states to change upon observation; thus, if anybody attempted to read the QKD, it would change, and the people involved would be immediately aware of the change.
QKD has already been successfully applied across short distances using fiber optic connections. The signal diminishes beyond 100 kilometers, and information transmission becomes sluggish beyond 300 kilometers. This distance problem can be greatly reduced by deploying satellites in low-Earth orbit (LEO) to broadcast and receive messages through line-of-sight.
LEO orbits can offer line-of-sight communication between earth-based ground stations up to 700 kilometers distant. However, this limitation can be overcome if the key is held in the satellite while it orbits or, better, by relaying the signal among linked satellites.
Fundamental Physics And Space Exploration
The ability of spacecraft to deliver navigational directions reduces as they travel further away from Earth. Naturally, “GPS” would be unavailable in deep space, and time lag durations for Earth-based control signals have risen as spacecraft go further away.
Furthermore, if such Earth-based navigational orders are not precise enough, the target vessel may entirely miss its destination. Sensors that detect the acceleration and rotation of a vehicle can enable navigation without needing external commands.
It is clear that the use of space-based technology is becoming more and more integral to our lives, and it is hard to know where these developments will lead. Significant breakthroughs in earth observation, space exploration, and secure communications are being made by deploying powerful quantum devices into space.