Three years ago, Jian-Wei Pan and his colleagues were able to quantum teleport information across 16 kilometers. This was one of the first major steps to the research team’s ultimate goal of teleporting photons to a satellite orbiting the Earth.
Once this is achieved, it will establish the first links of the quantum Internet, which harnesses the powers of subatomic physics in order to create a super-secure global communication network. In 2016, China plans on launching a satellite dedicated to quantum science experiments, ahead of the ESA and NASA.
When the satellite is launched, Pan and Anton Zeilinger, a physicist at the University of Vienna, plan on creating the first intercontinental quantum-secured network, connecting Asia to Europe by satellite.
Quantum objects exist in a superposition of many states, as particles and waves. This is described in a particle’s wavefunction, which gives the probability that it is in each of those states. When the particle’s properties are measured, the wavefunction collapses, choosing a definite state in a single location. The quantum property of entanglement between particles can be correlated with measurements, even if they are separated by huge distances. Quantum superposition demands that these properties cannot be fixed until measured.
Zeilinger was able to show that buckyballs, fullerene molecules containing 60 carbon atoms, can exhibit both wave and particle behavior. Quantum teleportation shows that all information about a quantum object can be scanned in one location and recreated in another, thanks to entanglement because operations carried out on one of the entangled particles affects the state of its partner, no matter how far away it is. The objects can be manipulated to transmit quantum information.
The data transmission of entangled particles is usually fraught with noise, scattering interactions which could destroy the delicate quantum correlations needed for teleportation to work. In order to transmit data beyond a city, it needs to be teleported through a satellite.
Currently, the record for quantum teleportation is 143 km, achieved by the Austrian team. Since the scientific concerns about teleporting to a satellite have been defused, the next step involves using one to test out quantum teleportation. The China National Space Administration stepped in after the ESA hesitated.
At these larger distances, general relativity starts to have an effect. Quantum theory and general relativity represent different conceptions of space and time, and physicists haven’t yet been able to unify them into a framework of quantum gravity.
Einstein postulates that space-time is perfectly smooth, even at infinitesimal scales. Quantum uncertainty implies that it’s impossible to examine space at such small distances. The satellite experiments could help determine when the rules of quantum theory apply over general relativity, and when the former starts to take effect.
It’s also an open question whether entangled particles will survive between space and Earth. If they don’t, physicists will have to look for an alternative theory to quantum mechanics. The satellite could also probe into the structure of space-time made by quantum-gravity theories. All of such theories predict that space-time becomes grainy beyond the scale of 1E-35 meters, i.e. the Planck length. Photons traveling from the satellite would be very slightly slowed and their polarizations would undergo a tiny, random rotation, which would be large enough to be detected at the ground station.