Isotropic phase number squeezing and macroscopic quantum coherence

Abstract

A new master equation performing isotropic phase-number squeezing is suggested. The phase properties of coherent superpositions are analyzed when the state evolves in presence of a bath with fluctuations squeezed in this isotropic way. We find that such a reservoir greatly improves persistence of coherence with respect to either a customary thermal bath, or to an anisotropically squeezed phase-sensitive bath.

Effects of entanglement in an ideal optical amplifier

“…An examination of Eq. (21) shows that the last factor in parentheses involving 0 α is strongly peaked when the value of α is near 0 gα , as would be expected from Fig. 3d.…”

“…2. Earlier studies of the amplification of cat states [4,[17][18][19][20][21][22][23][24][25][26][27][28] did not consider the limit of 1 g → or the interferometer approach of Fig. 2.…”

“…1. For an OPA, 21 in N g q = − − , where ˆi n q is the x quadrature in the idler mode. The same results apply to any ideal linear amplifier, including those based on an inverted atomic medium [9].…”

Quantum Tomography

“…Notice that any couple of quadratures X ϕ , X ϕ+π/2 is canonically conjugate, namely [X ϕ , X ϕ+π/2 ] = i/2, and it is equivalent to position and momentum of a harmonic oscillator. Usually, negative values of the Wigner function are viewed as signature of a non-classical state, the most eloquent example being the Schrödinger-cat state [40], whose Wigner function is characterized by rapid oscillations around the origin of the complex plane. From Eq.…”

Repeatable two-mode phase measurement

“…Finally-more interesting for foundations-a repeatable phase measurement is a good candidate for detecting Schrödinger-cat states (see, for example, Ref. [7]).…”