We show that the sender and the receiver each require coherent devices in order to achieve unconditional continuous variable quantum teleportation (CVQT), and this requirement cannot be achieved with conventional laser sources, linear optics, ideal photon detectors, and perfect Fock state sources. The appearance of successful CVQT in recent experiments is due to interpreting the measurement record fallaciously in terms of one preferred ensemble (or decomposition) of the correct density matrix describing the state. Our analysis is unrelated to technical problems such as laser phase drift or finite squeezing bandwidth.

• Received 20 November 2000

DOI:https://doi.org/10.1103/PhysRevLett.87.077903