  We experimentally demonstrate a high-efficiency Bell state measurement for
time-bin qubits that employs two superconducting nanowire single-photon
detectors with short dead-times, allowing projections onto two Bell states,
|Psi>- and |Psi+>. Compared to previous implementations for time-bin qubits,
this yields an increase in the efficiency of Bell state analysis by a factor of
thirty.
