First Object Teleported From Earth To Orbit (technologyreview.com)

Researchers in China have teleported a photon from the ground to a satellite orbiting more than 500 kilometers above. From a report: Last year, a Long March 2D rocket took off from the Jiuquan Satellite Launch Centre in the Gobi Desert carrying a satellite called Micius, named after an ancient Chinese philosopher who died in 391 B.C. The rocket placed Micius in a Sun-synchronous orbit so that it passes over the same point on Earth at the same time each day. Micius is a highly sensitive photon receiver that can detect the quantum states of single photons fired from the ground. That's important because it should allow scientists to test the technological building blocks for various quantum feats such as entanglement, cryptography, and teleportation. Today, the Micius team announced the results of its first experiments. The team created the first satellite-to-ground quantum network, in the process smashing the record for the longest distance over which entanglement has been measured. And they've used this quantum network to teleport the first object from the ground to orbit. Teleportation has become a standard operation in quantum optics labs around the world. The technique relies on the strange phenomenon of entanglement. This occurs when two quantum objects, such as photons, form at the same instant and point in space and so share the same existence. In technical terms, they are described by the same wave function.

Comments

A photon is not an "object"

[CajunArson]

Outside of an arbitrary definition that says a photon is an object because we say so, a photon is most certainly not an "object" using any ordinary definition of the term or even a definition that the vast majority of physicists would use (i.e. than an "object" has mass, which photons most certainly don't have or else they would never be able to travel at light speed).

Re:Stock Traders

[CSMoran]

Entanglement does not transfer information.

Quantum "teleportation" is badly misnamed

[gotan]

What it means is, that the quantum state from a particle on Site A is transferred to a particle on Site B. This involves an entangled state of two particles in A and B. Depending on the experimental set up the entangled particle in site B may be the object the quantum state is transferred to. The "teleportation" involves a measurement in Site A, and to completely transfer the quantum state to B one needs the (classical) result of this measurement at site B.

Re:Quantum "teleportation" is badly misnamed

[nickersonm]

You cannot tell that anything has happened by just looking at one of the entangled particles, no.

On a very brief and undetailed level, entanglement just says that measurements of particles A & B are correlated. What happens in an entangled measurement is vaguely like this:

1. Particles A & B are two-state systems: when measured in a certain way, they can either be a 1 or a 0. Before being measured, they are some combination of 1 and 0 and thus have a probability of being measured 1 or 0, but are not either.
2. Particles A & B are now entangled and in a state such that each individually has a 50% chance of being either 1 or 0.
3. Without being measured, B is moved to a long distance away.
4. A is measured.
5. When B is measured, it will be !A (100% of the time if the entanglement is perfect).
6. The important part is that the people measuring B don't know what A was until someone tells them via a classical channel.
7. If one makes continuous measurements of a stream of Bs (B1, B2, ...), they see a random pattern of 1s and 0s.
8. The people measuring a stream of As see a random pattern of 1s and 0s, but the interesting part is the A1...An is exactly !(B1...Bn) (anticorrelated)! You can't use this to send a signal, since each measurement is itself random, but if team A sent classical messages of their results, team B could predict the measurements of B.

Using further methods like mixing A with C and also B with D before measuring and other stuff, then telling each other what measurements of A&C resulted, it's possible to say that D4 == C4 exactly, 'teleporting' particle C4 (i.e. just reproducing the exact quantum state), but this requires measuring D1, D2, and D3 and thus destroying their state. It's more complicated than this, but resembles a logic puzzle.

Re:Quantum "teleportation" is badly misnamed

[Baloroth]

Not really. The problem is that we didn't take a photon in the lab, and create an identical photon in space. We took a photon in the lab, created a photon in space, then made the photon in space identical to the photon in the lab. That's a bit like taking a block of marble and carving it into *exactly* the same shape as, say, Michelangelo's David, then claiming we "teleported" the statue. Even if the final product is molecule for molecule identical, few people would call it "teleportation". Teleportation would involve taking the particles from one location and transferring them to the other, in some kind of stream or through a wormhole or something. Note that this is probably impossible.

The key to quantum "teleportation" is that particles are indistinguishable except for a couple of quantum numbers, so if we take a particle and force it to have the same numbers as another particle, we've "teleported" it. Except that we can also distinguish particles based on position. Yes, it's true that you can take two electrons in two hydrogen atoms, exchange them, and you'd never know the difference. But we can still say the electron in that hydrogen atom over there is not the same electron as the electron in this hydrogen atom a million miles away. This isn't just a philosophical distinction: the two electrons really are different (i.e. have different quantum wavefunctions), at a physics level.

Re:Too many words, mismash

[Bill Hayden]

Technically, teleported is the correct word. We're talking teleportation in the scientific sense, not Star Trek teleportation -- not that the unwashed masses know the difference.

I'd actually say that "object" is the wrong word. I'm not sure I'd call a photon an object. "Particle" would be 1000% better, and much less confusing.

Re:Too many words, mismash

[penandpaper]

No not technically. Did particle A starting in position X end up at position Y? Was any information transferred or able to be transferred? Is faster than light communication possible? The answer to all these are no. Describing entanglement with teleportation is dumb.

https://en.wikipedia.org/wiki/...

Great job on whoever named this teleportation

[Headw1nd]

Scientists: laypeople are twisting our words and making hyperbolic claims based on their misunderstanding of our research.

Other Scientists: Hey let's name this phenomenon after a fantastical and thematically similar yet completely unrelated concept in popular culture.

Re:Too many words, mismash

[slew]

No not technically. Did particle A starting in position X end up at position Y? Was any information transferred or able to be transferred? Is faster than light communication possible? The answer to all these are no. Describing entanglement with teleportation is dumb.

https://en.wikipedia.org/wiki/...

Actually, quantum information was transferred. Of course there wasn't faster than light communication as quantum teleportation relies on entanglement *and* a classical communication channel.

For each qubit of information that wants to be sent, one of a pair of entangled photons needs to be conveyed to the destination (which can be done at nearly lightspeed for photons in free-space). After this is conveyance is done, then anytime later, a qubit from a third photon can be "teleported" to the destination by use of a conventional communication channel (which obviously isn't faster than light speed).

The way this works is you jointly measure the 3rd photon and your local singleton of the previously entangled photon which yields one of 4 joint states. This doesn't tell you the original state of the 3rd photon, only the joint state relative to the entangled photon, (but in the process collapses the state of these photons).

You then send this description of the measurement (basically two bits of information) across a classical channel to the destination (at whatever speed you want).

To replicate the quantum state at the destination, you manipulate the phase of the previously conveyed/entangled photon (without measuring it) according to on the results of the relative (2-bit) state description. After this manipulation, this previously conveyed entangled-photon has a non-collapsed replicated quantum state of the original 3rd photon, but the state was transmitted/teleported to its destination over a classical channel.

You can read the details from their paper paper. Over 32 days, they managed 911 four-photon events and achieved an estimated accuracy of about 80% of conveying the quantum state (the theoretical limit accuracy of a conventional channel was about 66% w/o using information obtained using measurements of previously conveyed entangled photons).

Remember you can't simply pre-measure a quantum state w/o collapsing it to determine the accuracy rate, so accuracy was determined statistically using two entangled pairs (which is why they needed to create a four-photon-event and for which it was hard to create a process for).

Baby steps.