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Phase Conjugation of Continuous Quantum Variables

N. J. Cerf·S. Iblisdir
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Abstract

The phase conjugation of an unknown Gaussian state cannot be realized perfectly by any physical process. A semi-classical argument is used to derive a tight lower bound on the noise that must be introduced by an approximate phase conjugation operation. A universal transformation achieving the optimal imperfect phase conjugation is then presented, which is the continuous counterpart of the universal-NOT transformation for quantum bits. As a consequence, it is also shown that more information can be encoded into a pair of conjugate Gaussian states than using twice the same state.

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N. J. Cerf, S. Iblisdir. 2000-12-05. Phase Conjugation of Continuous Quantum Variables. https://doi.org/10.1103/physreva.64.032307

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