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Chinese Physicists Achieve Quantum Teleportation Over 60 Miles
MrSeb writes "Chinese physicists are reporting that they've successfully teleported photonic qubits (quantum bits) over a distance of 97 kilometers (60mi). This means that quantum data has been transmitted from one point to another, without passing through the intervening space. It's important to note that the Chinese researchers haven't actually made a photon disappear and reappear 97 kilometers away; rather, they've used quantum entanglement to recreate the same qubit in a new location, with the same subatomic properties as the original qubit. The previous record for transmitting entangled qubits was 16 kilometers, performed by another Chinese team back in 2010 — and perhaps most excitingly, the researchers seem confident that their system will scale up from 97km to distances capable of reaching orbital satellites, at which point we'll actually be able to build a global quantum network for all of our cryptographic needs."
I hear the next step is transporting economic superpower status over 7,000 miles.
What political party do you join when you don't like Bible-thumpers *or* hippies?
Lord... Whats a qubit?
Don't blame me, I voted for Kodos
You can't transmit meaningful information with quantum teleportation alone, you still need a classical channel that operates by conventional means unless you want to transmit uncontrollable random garbage.
"When information is power, privacy is freedom" - Jah-Wren Ryel
The information contained in the qbit is transported from one entangled photon to another, but you first must get that entangled photon to the destination via more conventional means. They're doing that with a laser.
This is part of an international research effort, including schools like Carnegie-Mellon in the US. However, due to the lower costs of photonic qubits in China, it only makes sense to have the majority of experiments carried out over there.
So that means the satellite television providers will be all over this.
This, and all other quantum "teleportation" and related entanglement phenomenon, do not allow for faster-than-light communication. The important thing to note is that the qubit is "teleported", not the photon itself: the photons are transmitted conventionally via some means (in this case, it looks like they did it through open air). Since the photons are entangled with a photon you retain, measuring one collapses the wave-function of the other and allows both parties to know what the state is simultaneously. The security ramifications are that any eavesdropper will collapse the wave-function before the receiver gets the photon, so he will not receive the photon in the same state as the receiver sent it.
You cannot, according to what we know of physics, use quantum entanglement to send information faster than light.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
Note that it's still limited by the speed of light. The key feature, however, is that it is secure: someone intercepting the photon can't copy or read its qbit state without breaking the quantum entanglement, or preventing it from reaching the destination. In either case, the receiver will immediately know that the channel has been broken. It then stops transmitting a response to the sender, and the sender perceives this as also a break in secure communications and stops transmitting. Both the sender and the receiver would then go into failure mode and send query/response polls periodically. When secure communications are re-established, they can resume transmitting data.
If we have a 72-kg (158 lb.) person made mostly out of water, that's about 4,000 moles, or 2.4x10^27 molecules, which is about 7.2x10^27 atoms. The actual number might be different, but it's way more than a trillion.
So it's replication, not teleportation?
It's not replication, the quantum state of one photon is transfered from one photon to another.
Here's an easy explanation. http://www.youtube.com/watch?v=_qmSdC7aQpY
Replication will never be possible as a quantum state cannot be copied: http://en.wikipedia.org/wiki/No-cloning_theorem
Ah, but the abstract of the paper itself says "Over a 35-53 dB high-loss quantum channel, an average fidelity of 80.4(9) % is achieved for six distinct initial states." That sounds like a lossy channel to me. Plus, I simply don't believe it's possible to send a laser beam over X kilometers, including an atmosphere, and have them ALL reach their destination - it's a limitation of the medium.
Also, the Physics ArXiv blog post for this paper includes this;
"Inevitably photons get lost and entanglement is destroyed in such a process. Imperfections in the optics and air turbulence account for some of these losses but the biggest problem is beam widening (they did the experiment at an altitude of about 4000 metres). Since the beam spreads out as it travels, many of the photons simply miss the target altogether. "
and
"That's interesting because it's the same channel attenuation that you'd have to cope with when beaming photons to a satellite with, say, 20 centimetre optics orbiting at about 500 kilometres. "The successful quantum teleportation over such channel losses in combination with our high-frequency and high-accuracy [aiming] technique show the feasibility of satellite-based ultra-long-distance quantum teleportation," say Juan and co."
So it looks to me as though even the paper's author is admitting some "channel losses". The question I still have is, how is it possible to distinguish channel losses from adversarial interception of photons?