Squeezed light and nonclassical motion in mechanics

S. Swain

Klemens Hammerer, Claudiu Genes, David Vitali +4 more

Florent Lecocq, J. B. Clark, Raymond W. Simmonds +2 more

By coupling a macroscopic mechanical oscillator to two microwave cavities, we simultaneously prepare and monitor a nonclassical steady state of mechanical motion. In each cavity, correlated radiation pressure forces induced by two coherent drives engineer the coupling between the quadratures of light and motion. We, first, demonstrate the ability to perform a continuous quantum nondemolition measurement of a single mechanical quadrature at a rate that exceeds the mechanical decoherence rate, while avoiding measurement backaction by more than 13 dB. Second, we apply this measurement technique to independently verify the preparation of a squeezed state in the mechanical oscillator, resolving quadrature fluctuations 20% below the quantum noise.

P. Tombesi, Edward R. Pike

Rajendra Pratap, Dilip Kumar Giri, Ajay Prasad

The nonclassical effects of light in the fifth harmonic generation are investigated by quantum mechanically up to the first-order Hamiltonian interaction. The coupled Heisenberg equations of motion involving real and imaginary parts of the quadrature operators are established. The occurrence of amplitude squeezing effects in both quadratures of the radiation field in the fundamental mode is investigated and found to be dependent on the selective phase values of the field amplitude. The photon statistics in the fundamental mode have also been investigated and found to be sub-Poissonian in nature. It is observed that there is no possibility to produce squeezed light in the harmonic mode up to first-order Hamiltonian interaction. Further, we have found that the normal squeezing in the harmonic mode directly depends upon the fifth power of the field amplitude of the initial pump field up to second-order Hamiltonian interaction. This gives a method of converting higher-order squeezing in the fundamental mode into normal squeezing in the harmonic mode and vice versa. The analytic expression of fifth-order squeezing of the fundamental mode in the fifth harmonic generation is established.

Vladimir P Bykov

From the fact of observation of squeezed light follows the possibility of a nonperturbing or nondemolition measurement (observation) of a single microscopic object in a widely distributed quantum-mechanical state. Macroscopic bodies—objects of classical mechanics—are usually found in states with narrow wave packets, although quantum mechanics does not forbid them to be in states with wide wave packets. The absence of macroscopic bodies in such states requires explanation. In this article it is shown that in virtue of a special, geometrical nature of the gravitational field the absence in nature of macroscopic bodies in widely distributed states can be due to the focusing action of the self-gravitational field of a macroscopic body on its wave packet. Thus, the gravitational field can play an important role in the relaxation of the classical limit of quantum mechanics.