Discussion:
[IP] Re First Object NOT Teleported from Earth to Orbit
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Dave Farber
2017-07-14 10:16:50 UTC
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Subject: Re: [IP] Re First Object NOT Teleported from Earth to Orbit
Date: July 14, 2017 at 3:05:34 AM EDT
This is the first time that any object has been teleported from Earth to
orbit...
No, no, no. It's not an object that was teleported. It was
information about an object that was teleported.
Uh, from looking at the article, NOTHING was teleported. They sent up
a satellite (using a chemical rocket) that contained some kind of
photon detector. They then sent photons from earth to the satellite,
via a more complicated way of shining light upward. No "teleportation"
was involved; the photons got from earth to orbit by the ordinary
motion of photons through space.
The quantum folks adopted a word ("teleportation") that actually means
https://en.wikipedia.org/wiki/Teleportation
https://en.wikipedia.org/wiki/Quantum_teleportation
Note that to "teleport" one quantum state requires doing classical
communication of two bits. This isn't an example of a science-fiction
quantum encrypting ansible that spits information instantly over vast
distances by using two local stores of entangled qubits. It doesn't
work faster than the speed of light. It's just quantum guys using
confusing terminology for some odd properties of matter.
John
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Dave Farber
2017-07-16 20:36:44 UTC
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Subject: Re: [IP] Re First Object NOT Teleported from Earth to Orbit
Date: July 14, 2017 at 9:29:40 AM EDT
In addition, I'm having some trouble with "photon" as a member of class "object".
Mary
Subject: Re: [IP] Re First Object NOT Teleported from Earth to Orbit
Date: July 14, 2017 at 3:05:34 AM EDT
This is the first time that any object has been teleported from Earth to
orbit...
No, no, no. It's not an object that was teleported. It was
information about an object that was teleported.
Uh, from looking at the article, NOTHING was teleported. They sent up
a satellite (using a chemical rocket) that contained some kind of
photon detector. They then sent photons from earth to the satellite,
via a more complicated way of shining light upward. No "teleportation"
was involved; the photons got from earth to orbit by the ordinary
motion of photons through space.
The quantum folks adopted a word ("teleportation") that actually means
https://en.wikipedia.org/wiki/Teleportation <https://en.wikipedia.org/wiki/Teleportation>
https://en.wikipedia.org/wiki/Quantum_teleportation <https://en.wikipedia.org/wiki/Quantum_teleportation>
Note that to "teleport" one quantum state requires doing classical
communication of two bits. This isn't an example of a science-fiction
quantum encrypting ansible that spits information instantly over vast
distances by using two local stores of entangled qubits. It doesn't
work faster than the speed of light. It's just quantum guys using
confusing terminology for some odd properties of matter.
John
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Dave Farber
2017-07-20 10:38:50 UTC
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Date: July 20, 2017 at 6:05:39 AM EDT
Subject: Re: [IP] Re First Object NOT Teleported from Earth to Orbit
(Dave, I sent this a day or two ago, but if you forwarded it on I missed it. More importantly, I’ve now updated to include the recently-announced Japanese satellite experiment I had missed!)
Gilmore is right.
To extend a little bit, what is “teleported” in quantum teleportation, is a quantum *state* that can’t be analyzed without destroying it. Essentially, you’re moving quantum data from one place to another without learning anything about the data itself; in quantum mechanics, when you measure a state, you destroy any superposition and any quantum entanglement it has, which destroys its usefulness as quantum data.
http://www.bbc.com/news/science-environment-40594387
Teleportation is useful not only for moving qubits over long distances, but also for changing physical data representations from e.g. the spin of an electron to the spin of a nucleus — roughly, moving a qubit from RAM to disk, if you like.
The experiment is an impressive accomplishment. Jian-Wei Pan’s group is the best in the world at long-distance single-photon work, bar none. He did his Ph.D. with Anton Zeilinger, in Vienna. After returning to China, he has built an incredible group, with tremendous support from the Chinese government. We all knew his team had put up a satellite, but personally I didn’t expect the data (and data rate) to be as good as it is — it’s a hard problem, capturing single photons sent down from orbit! And yet they’ve done it, beating out teams from Canada, Singapore, Japan and Europe that were already doing preliminary experiments, including in space. See e.g.
https://www.wired.com/2017/02/physicists-test-quantum-cryptography-playing-catch-photons-plane/
http://www.nict.go.jp/en/press/2017/07/11-1.html
http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2017.107.html?foxtrotcallback=true
They are *not* sending entangled photon pairs to two ground satellites, or creating space-to-ground entanglement. In fact, they’re not using single-photon pulses at all. They are sending pulses with 2.3*10^8 photons/pulse from the satellite, and receiving an average of 0.1 photons on the ground, after a 78dB loss budget. This is also an extraordinary accomplishment, even if it’s a bit eclipsed by the successive Chinese announcements. If you consider a satellite to be a trusted node, and you connect via QKD to two separate ground stations, you can create ground station-to-ground station shared secret keys securely.
Several years ago, Simon Devitt and his collaborators, including yours truly, proposed an alternative to creating entanglement via satellite: shipping error correction-protected qubits via container ship. At the time, I contended that satellite was too hard to pull off across the Pacific, and the first trans-pac entanglement demonstration would be using our technique. Now, I’m not so sure.
https://motherboard.vice.com/en_us/article/4x34e3/how-cargo-ships-full-of-diamond-hard-drives-could-connect-a-quantum-sneakernet
https://www.nature.com/articles/srep36163
This October, we are doing a free MOOC on quantum computing. I’ll send details in a separate email.
https://www.futurelearn.com/courses/intro-to-quantum-computing/
Subject: Re: [IP] Re First Object NOT Teleported from Earth to Orbit
Date: July 14, 2017 at 9:29:40 AM EDT
In addition, I'm having some trouble with "photon" as a member of class "object".
Mary
Subject: Re: [IP] Re First Object NOT Teleported from Earth to Orbit
Date: July 14, 2017 at 3:05:34 AM EDT
This is the first time that any object has been teleported from Earth to
orbit...
No, no, no. It's not an object that was teleported. It was
information about an object that was teleported.
Uh, from looking at the article, NOTHING was teleported. They sent up
a satellite (using a chemical rocket) that contained some kind of
photon detector. They then sent photons from earth to the satellite,
via a more complicated way of shining light upward. No "teleportation"
was involved; the photons got from earth to orbit by the ordinary
motion of photons through space.
The quantum folks adopted a word ("teleportation") that actually means
https://en.wikipedia.org/wiki/Teleportation
https://en.wikipedia.org/wiki/Quantum_teleportation
Note that to "teleport" one quantum state requires doing classical
communication of two bits. This isn't an example of a science-fiction
quantum encrypting ansible that spits information instantly over vast
distances by using two local stores of entangled qubits. It doesn't
work faster than the speed of light. It's just quantum guys using
confusing terminology for some odd properties of matter.
John
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