1,876 research outputs found
Methods for linear optical quantum Fredkin gate
We consider the realization of quantum Fredkin gate with only linear optics
and single photons. First we construct a heralded Fredkin gate using four
heralded controlled-not (CNOT) gates. Then we simplify this method to a
post-selected one utilizing only two CNOT gates. We also give a possible
realization of this method which is feasible with current experimental
technology. Another post-selected scheme requires time entanglement of the
input photons but needs no ancillary photons.Comment: 5 pages, 5 figure
Stability of Phase-modulated Quantum Key Distribution System
Phase drift and random fluctuation of interference visibility in double
unbalanced M-Z QKD system are observed and distinguished. It has been found
that the interference visibilities are influenced deeply by the disturbance of
transmission fiber. Theory analysis shows that the fluctuation is derived from
the envioronmental disturbance on polarization characteristic of fiber,
especially including transmission fiber. Finally, stability conditions of
one-way anti-disturbed M-Z QKD system are given out, which provides a
theoretical guide in pragmatic anti-disturbed QKD.Comment: 9 pages, 3 figue
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