  We propose a compact and highly-efficient scheme for complete Bell-state
analysis using two-photon absorption in a superconducting proximity region of a
semiconductor avalanche photodiode. One-photon transitions to the
superconducting Cooper-pair based condensate in the conduction band are
forbidden, whereas two-photon transitions are allowed and are strongly enhanced
by superconductivity. This Cooper-pair based two-photon absorption results in a
strong detection preference of a specified entangled state. Our analysis shows
high detection purity of the desired Bell state with negligible false detection
probability. The theoretically-demonstrated concept can pave the way towards
practical realizations of advanced quantum information schemes.

Quantum Physics;Mesoscale and Nanoscale Physics;Superconductivity