We give a description of balanced homodyne detection (BHD) using a conventional laser as a local oscillator (LO), where the laser field outside the cavity is a mixed state whose phase is completely unknown. We apply our description to continuous-variable quantum teleportation (CVQT) with a laser, and show that CVQT with a laser is valid only if the unknown phase of the laser field is shared among sender’s LOs, the EPR state, and receiver’s LO. We also propose a method to generate a strongly phase-correlated quantum state necessary for CVQT without an additional optical path.

• Received 9 January 2003

DOI:https://doi.org/10.1103/PhysRevA.68.050302