Security of QKD-systems with detector efficiency mismatch

摘要: The rules of quantum mechanics makes it possible to exchange a secret key at distance. This is called distribution (QKD). In theory the can be made completely secure. Real QKD implementations however, has numerous imperfections. Luckily one also been able prove security with large variety field matured over recent years, and now reached commercial applications photons as bits, optical fibers channel. Today there are least three vendors QKD-systems. We live in times hacking. Researchers begun task breaking Many new imperfections discovered, some which might used break QKD. thesis study detector efficiency mismatch loophole. Most QKD-systems require two detectors, virtually impossible make identical detectors exact same efficiency. What worse, turns out that eavesdropper often control relative efficiencies trough domain, for instance by controlling timing, frequency or spacial mode photons. turn gain information about key. Previously best known attack would compromise if 1:15. Here current attacks on systems improved 1:4. less than found QKD-system, so could principle eavesdrop this QKD-system. One try close loophole modifying implementation. suggestion four state Bob. problem patch will open other loopholes, these loopholes reopen remove Eves doing sufficient amount extra privacy amplification. general bound presented, quantifying required amplification Eve's proof more previous proof, valid any basis dependent, possibly lossy, linear channel receiver/detectors. Since realistic assumptions QKD-implementation, represents major step closing real devices.