Quantum Teleportation to the Micius Satellite Explained

In 2017 a Chinese team led by physicist Jian-Wei Pan reported the first quantum teleportation from a ground station to a satellite. What travelled was not a photon, an object or a person: it was the quantum state of a single photon, recreated on another photon aboard the Micius satellite at distances of up to about 1,400 km. That distinction is the key to understanding what the experiment achieved and why it mattered for a future quantum internet.

Here is what happened, how quantum teleportation works in plain language, and what it can and cannot do.

What the Micius experiment actually did

Micius, officially the Quantum Experiments at Space Scale (QUESS) mission, was launched from the Jiuquan centre in August 2016 into a sun-synchronous orbit roughly 500 km high. It was built to test several building blocks of quantum communication in space: distributing entangled photons, quantum key distribution for encryption, and teleportation.

For the teleportation test, the team worked from a ground station at Ngari in Tibet, chosen for its high altitude and thin, dry air. They prepared single photons in a series of quantum states and teleported those states to photons on the satellite as it passed overhead. The results, first posted on arXiv in July 2017 and published in Nature on 7 September 2017 (Ren et al.), covered satellite-to-station distances from about 500 km to 1,400 km.

Success is measured by fidelity, a number that shows how closely the received state matches the one that was sent. The team reported an average fidelity of 0.80 across six different input states. That beats the best possible score of about 0.67 that any classical, non-quantum method could reach, which is how physicists know the transfer was genuinely quantum. You can read the team’s paper on arXiv.

How quantum teleportation works

The protocol was proposed in 1993 by Charles Bennett, Gilles Brassard and four colleagues. It relies on entanglement, a link between particles whose properties can only be described together, not one by one. Measure one member of an entangled pair and the outcomes on the other are correlated in ways no classical system can mimic.

In simplified steps, teleportation works like this:

• The sender and receiver share an entangled pair of photons, one each.
• The sender takes the photon carrying the state to be transferred and performs a joint measurement on it together with their half of the entangled pair.
• That measurement destroys the original state on the sender’s side and produces two ordinary bits of information.
• Those bits are sent by a normal, classical channel. Using them, the receiver applies a correction to their photon, which then carries the original state.

Two things follow. The original is not copied, because it is consumed in the measurement, which keeps the process consistent with the “no-cloning” rule of quantum mechanics. And nothing travels faster than light, because the receiver cannot finish the job until the classical bits arrive.

Why use a satellite at all?

Single photons are fragile messengers. In optical fibre they are gradually absorbed and scattered, and in the open air near the ground they are blocked by turbulence, haze and obstacles. As the team explained to MIT Technology Review, previous teleportation experiments between distant locations were limited to a distance on the order of 100 kilometres.

Going to space changes the geometry. Most of the path between Ngari and Micius ran through near-vacuum, and only the last stretch passed through the dense lower atmosphere. Even so, the link lost a huge share of photons, and pointing a narrow beam at a satellite moving across the sky demanded very precise tracking. The researchers generated entangled photon pairs on the ground at about 4,000 per second, sent one photon of each pair upward and kept the other, then compared measurements on both ends to confirm the link worked.

The same satellite also set records for distributing entangled photons to ground stations about 1,200 km apart, and it later supported quantum-encrypted communication between China and Austria. Teleportation was one part of a wider test programme for long-distance quantum networks.

Where it fits in the history of teleportation

The first laboratory demonstrations came in 1997, from groups in Rome and in Innsbruck (the latter led by Anton Zeilinger, who later shared the 2022 Nobel Prize in Physics for work on entanglement). Over two decades, experiments stretched from a lab bench to kilometres of fibre and open-air links across lakes and between islands.

In September 2016 two teams moved teleportation into real city fibre networks: one across about 6.2 km of fibre in Calgary, Canada, and another over about 6.5 km between independent sources in Hefei, China. Micius took the next big step by adding an orbiting endpoint, pushing the distance far beyond what ground links had achieved at the time.

Common myths about quantum teleportation

“Something was beamed into space.” No matter left Earth through teleportation. Photons were sent up as an ordinary light beam; what was teleported was the information describing one photon’s quantum state. Some headlines at the time called it the first “object” teleported to orbit, which overstated the result.

“It allows instant messaging across any distance.” Because the receiver needs classical bits to complete each transfer, teleportation cannot send usable information faster than light.

“People will be teleported next.” Teleporting even one photon’s state is demanding; the number of particles in a human body, and the need to capture and reconstruct all their states, places human teleportation firmly in science fiction.

“Entanglement means the particles are physically connected.” They share correlations, not a hidden wire. The correlations are real and measurable, but they do not carry a signal on their own.

What it means for a quantum internet

A future quantum internet would link quantum computers and sensors, and make it possible to share encryption keys whose security rests on physics rather than on hard maths problems. Teleportation is a core tool for that vision because it moves quantum information without sending the fragile carrier itself over the whole distance. The Micius team called their work an essential step toward global-scale quantum internet.

Major hurdles remain: daylight operation, higher data rates, quantum memories that can store states while classical signals catch up, and networks of satellites and ground repeaters. Still, the 2017 result showed that the basic physics holds up over planetary distances, and it set a benchmark that later experiments have been building on ever since.

Sources: Ren et al., Ground-to-satellite quantum teleportation (arXiv / Nature 2017); MIT Technology Review; Wikipedia: Quantum teleportation; Wikipedia: Quantum Experiments at Space Scale; earlier coverage by Futurism.