Squeezed states and the classical limit

Vasileios Bartzis, E. Vlahos, A. D. Jannussis

Menno Poot, King Yan Fong, Hong X. Tang

Using a stabilizing quadrature-feedback scheme the thermal motion of an on-chip opto-electromechanical resonator is squeezed far beyond the limit of classical parametric squeezing. It is shown that feedback on the Y quadrature by itself can already squeeze the thermal motion of the resonator, but the maximum achievable squeezing level is limited by the imprecision noise. By combining the feedback and parametric pumping a record of 15.1 dB of classical noise squeezing is demonstrated. This not only largely exceeds the 3 dB limit for regular squeezing, but is also deeper than ever can be achieved with feedback cooling. The detector-resonator interaction is analyzed within the semi-classical framework and it is shown that using this feedback-stabilized parametric pumping technique true quantum-squeezed states can be prepared when the resonator starts off close to its ground state, and that the ultimate amount of squeezing depends on the minimum detuning that can be achieved.

L. Chen, Shulei Bi, Bao zhu Lu

Stable, low noise, infrared squeezed state tight at 1064 nm is generated by utilizing optical parametric down-conversion (OPDC) technique based on periodically poled KTiOPO 4 in a optical parametric amplifier (OPA) resonator. A non-classical noise reduction of 2.58 dB below the shot noise is observed through balanced homodyne detection. The squeezed state light is used to set up an imaging system for high-resolution imaging, and it is found that the resolution of image based on the amplitude-squeezed light is 1.26 times larger than that of infrared coherent light under the same intensity. The experimental results indicate that squeezed light is an important non-classical light, which can overcome the coherent laser shot-noise, the classical diffraction limit and limit of quantum noise.

A. D. Jannussis, Vasileios Bartzis

Alekseev, K N, Primak, D S

We examine the dynamics of a wave packet that initially corresponds to a coherent state in the model of quantum kicked rotator. This main model of quantum chaos, which allows for a transition from regular to to chaotic behavior in the classical limit, may be realized in experiments with cold atoms. We study the generation of squeezed states in the quasiclassical limit and in a time interval when quantum-classical correspondence is yet well-defined. We find that the degree of squeezing depends on the degree of local instability in the system and increases with the Chirikov parameter of stochasticity. We discuss the dependence of the degree of squeezing on the initial width of the packet, the problems of stability and observability of squeezed states at the transition to quantum chaos, as well as the dynamics of wave packet destruction.

P. L. Knight, Vladimír Bužek