I haven't verified the results of this particular paper, but there is a broad class of potential problems along these lines with quantum cryptography. Here's a short piece I wrote about these problems in 2004: <a href="http://michaelnielsen.org/blog/whats-wrong-with-those-quantum-cryptosystems/" rel="nofollow">http://michaelnielsen.org/blog/whats-wrong-with-those-quantu...</a><p>The short summary is that side channel attacks are a real problem with quantum cryptography, potentially moreso than with conventional crypto. The reason is that only a limited number of people have the resources to seriously test (and thus improve) real-world implementations of quantum cryptosystems systems. I.e., quantum crypto greatly raises the bar to do white hat hacking.