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Quantum Cryptography Conquers Noise Problem
ananyo writes "Quantum-encryption systems that encode signals into a series of single photons have so far been unable to piggyback on existing telecommunications lines because they don't stand out from the millions of others in an optical fiber. But now, physicists using a technique for detecting dim light signals have transmitted a quantum key along 90 kilometers of noisy optical fiber. The feat could see quantum cryptography finally enter the mainstream. The researchers developed a detector that picks out photons only if they strike it at a precise instant, calculated on the basis of when the encoded photons were sent. The team's 'self-differentiating' detector activates for 100 picoseconds, every nanosecond. The weak charge triggered by a photon strike in this short interval would not normally stand out, but the detector measures the difference between the signal recorded during one operational cycle and the signal from the preceding cycle — when no matching photon was likely to be detected. This cancels out the background hum. Using this device, the team has transmitted a quantum key along a 90-kilometer fiber, which also carried noisy data at 1 billion bits per second in both directions — a rate typical of a telecommunications fiber."
Where can I get buy my personal quantum crypto kit?
Tomorrow is another day...
"transmitted a quantum key along a 90-kilometer fiber, which also carried noisy data at 1 billion bits per second in both directions — a rate typical of a telecommunications fiber."
Telecommunications fiber with a 90km (~50mi.) length would be considered backbone. Typically two fibers are used to send signal in both directions. Single fiber applications require different frequencies of light to both TX & RX. This single fiber application is only used in metro FTTX/GPON situations - never in backbone as the frequency splitting equipment adds relatively high amounts of loss to your signal, impacting how far you can go without regeneration.
Send a handshake message used to calculate transit time, and then another to specify when the next packet will be sent, or at what intervals. If it fails redo the handshake.
love is just extroverted narcissism
Shouldn't it be more like, quantum tamper detection? It's just using one-time pad in such a way that the pad's transmission getting intercepted will trigger the tamper detection mechanism.
"Screw Sun, cross-platform will never work. Let's move on and steal the Java language." - Visual J++ Product Manager
While the hardware challenges are undoubtedly substantial, the basic idea is just a variation on time division multiplexing, which has been extensively used since the days of the telegraph, well before 1900. If this receives a patent, I hope it is for some hardware advance and not just because of the sharing of the fibre.
There are numerous problems:
1. You need _optical_ switches, i.e. switched circuits. That approach failed a long time ago. Anybody remember ATM?
2. 90km is nothing. Amplification is impossible, so unless they reach 10'000km, this is completely irrelevant.
3. Nobody needs it. Cryptography does fine. (No, this is at best "quantum modulation", no crypto involved.) If you are paranoid, use OTPs. They are far, far cheaper, far, far more reliable and completely compatible with existing networks.
4. Remember, this is only key exchange, not actual data transmission. As such it is pretty useless, as you still need to rely on cryptography for the message transfer.
5. The security guarantees are far, far weaker than people are made to believe. Just look at the history of successful compromises.
6. Not even the physics may work out. Quantum theory is a _theory_, not established fact.
Another worthless stunt.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.