Investigation of Quantum Phase Measurement

J. W. Noh, A. Fougères, L. Mandeļ

It is pointed out in response to Hradil and Bajer [preceding Comment, Phys. Rev. A 48, 1717 (1993)] that C${\mathrm{^}}_{\mathit{M}}$ and S${\mathrm{^}}_{\mathit{M}}$ cannot both be measured together by scheme 1, whereas they can by scheme 2. There is no phase angle whose cosine and sine both vanish, and putting C+iS equal to zero for certain measurement outcomes breaks the connection with phase.

Z. Hradil

L. Mandeļ

Manabendra Nath Bera, R. Prabhu, Aditi Sen De +1 more

We employ a genuine multipartite entanglement measure, the generalized geometric measure, for investigating the quantum phase transition in an infinite quantum spin-1/2 chain with two-spin as well as three-spin interactions. We show that in contrast to bipartite entanglement of the ground state, the genuine multiparty one unerringly indicates the quantum phase transition in the system. The system lends itself to a complementary behavior between bipartite and genuine multipartite entanglements. We also investigate the trend of the multipartite entanglement in finite chains, in which we perform a finite-size scaling to confirm the signature of the quantum phase transition already in finite systems. The finite-size investigation renders the phenomenon to be observable in real systems.

Tatsuki Tahara, Ryo Okamoto

We numerically investigate the effect of quantum fluctuation in phase-shifting interferometry. Numerical results agree well with the theoretical ones and confirm the limit of measurement accuracy and a trade-off relationship between amplitude and phase.

J. D. Franson