Complementary coherent state for measuring the Q-function: generation and properties

Ardiley Torres Avelar, B. Baseia, N. G. de Almeida

In a previous paper a proposal for measuring the Husimi Q -function based on the projection synthesis method (Barnett and Pegg 1996 Phys. Rev. Lett. 76 4148) was presented. The scheme required the presence of an unavailable state, named the complementary coherent state. This paper shows how to generate this state in travelling waves and studies its properties.

Max A. Lohe, Lawrence C. Biedenharn

Jean-Pierre Antoine, Bagarello, Fabio, Jean‐Pierre Gazeau

Guillaume Thekkadath, Rebecca Y. Saaltink, Lambert Giner +1 more

In a classical world, simultaneous measurements of complementary properties (e.g., position and momentum) give a system's state. In quantum mechanics, measurement-induced disturbance is largest for complementary properties and, hence, limits the precision with which such properties can be determined simultaneously. It is tempting to try to sidestep this disturbance by copying the system and measuring each complementary property on a separate copy. However, perfect copying is physically impossible in quantum mechanics. Here, we investigate using the closest quantum analog to this copying strategy, optimal cloning. The coherent portion of the generated clones' state corresponds to "twins" of the input system. Like perfect copies, both twins faithfully reproduce the properties of the input system. Unlike perfect copies, the twins are entangled. As such, a measurement on both twins is equivalent to a simultaneous measurement on the input system. For complementary observables, this joint measurement gives the system's state, just as in the classical case. We demonstrate this experimentally using polarized single photons.

Wei Ye, Weidong Zhou, Haoliang Zhang +3 more

Abstract We propose a theoretical protocol to generate a kind of non-Gaussian state—a Laguerre polynomial excited coherent state (LPECS) by exploiting a two-mode squeezing transformation and a conditional measurement with a coherent state input. Then we investigate the nonclassical features of the LPECS according to the Glauber–Sudarshan P ( α ) function, photon number distribution, Mandel’s Q parameter, second-order correlation function, and squeezing properties as well as negative Wigner distribution. Our results show that the generated output state presents obvious nonclassical properties which can be modulated by a coherent amplitude, a squeezing parameter and a conditional measurement. In particular, the squeezing and negative Wigner function are clear.

K. Thirulogasanthar, G. Honnouvo, G. Honnouvo