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Quantum phase estimation using path-symmetric entangled states
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DOI：10.1038/srep30306.png)
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We study the sensitivity of phase estimation using a generic class of path-symmetric entangled states |phi >vertical bar 0 > + vertical bar 0 >vertical bar phi >, where an arbitrary state vertical bar phi > occupies one of two modes in quantum superposition. With this generalization, we identify the fundamental limit of phase estimation under energy constraint that is characterized by the photon statistics of the component state vertical bar phi >. We show that quantum Cramer-Rao bound (QCRB) can be indefinitely lowered with super-Poissonianity of the state vertical bar phi >. For possible measurement schemes, we demonstrate that a full photon-counting employing the path-symmetric entangled states achieves the QCRB over the entire range [0, 2 pi] of unknown phase shift phi whereas a parity measurement does so in a certain confined range of phi. By introducing a component state of the form vertical bar phi > = root q vertical bar 1 + root 1-q vertical bar N >, we particularly show that an arbitrarily small QCRB can be achieved even with a finite energy in an ideal situation. This component state also provides the most robust resource against photon loss among considered entangled states over the range of the average input energy N-av > 1. Finally we propose experimental schemes to generate these path-symmetric entangled states for phase estimation.
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3.9
论文数:
27.8W
被引数:
83.5W
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