Quantum effects in radiation-pressure-dominated optomechanical systems

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

Next-generation interferometric gravitational-wave (GW) detectors, such as the Advanced LIGO detectors, will be limited by quantum noise at almost all frequencies in the GW band: radiation-pressure noise at low frequencies and shot noise at high frequencies. This quantum noise limit (QNL) is reached due to extremely high circulating laser power, in addition to mitigation of other classical noise sources. Studying quantum noise limits and finding ways to circumvent them is important not only for improved performance of future GW detectors, but also allows for the study of fundamental quantum effects, such as squeezing and entanglement, in macroscopic mechanical systems. This award supports an experimental research program to generate and characterize quantum states arising from the interaction of light with macroscopic mechanical systems, with the goal to better understand the fundamental limits of quantum measurement, as well as to improve the performance of interferometric gravitational-wave detectors. The centerpiece of the research program is a meter-scale interferometer with low-mass suspended mirrors, high circulating power, and a quantum-limited readout. Experiments will be conducted to study the following radiation pressure induced phenomena, using variants of this single apparatus: (1) Observation of ponderomotive squeezing, a novel alternative to the more traditional use of nonlinear optical media, that relies on the fundamental quantum mechanics of the shot noise and radiation-pressure noise correlations in an optomechanical oscillator system. This is one of the hallmarks of quantum effects in quantum-noise-dominated gravitational-wave interferometers, such as the Advanced LIGO detectors, and warrants studying in prototype interferometers. (2) Observation of ground state cooling of a macroscopic object is possible because radiation pressure can be used to reduce the motion of objects without introducing thermal noise---a much sought after goal in the realm of quantum measurement. (3) Observation of quantum entanglement, arising from radiation pressure induced coupling of the motion of the mirror and the quantum radiation field. (4) Direct observation quantum radiation pressure noise. Advanced LIGO is expected to be limited by quantum radiation pressure noise in the lowest part of its detection band, and studying the interaction of this noise source with the optomechanical system is likely to reveal deeper understanding, or even new physics. None of these phenomena have been observed experimentally to date. The main purpose of this research program is to gain further understanding of radiation-pressure dominated interferometers, an important feature of next-generation gravitational wave detectors. Equally attractive is the prospect of exploring the fundamental physics of quantum correlations due to optical-mechanical couplings in a macroscopic mechanical oscillator system. The broader impact of the proposed work lies in its scientific and its personnel diversity. The scientific diversity arises from the necessarily cross-disciplinary nature of the proposed research: it combines the techniques and formalism of quantum optics and quantum measurement theory with gravitational-wave detection. The personnel diversity is the outcome of aggressive recruitment of women and minority students by the PI (herself a member of minority groups), through her own efforts as well as those of the outreach programs of the LIGO Laboratory and MIT. In addition, the sub-QNL measurements are popular with students and generate considerable enthusiasm with the public as well. The proposed experiments share common technologies with quantum teleportation, quantum information, quantum control and condensed matter physics (nano- and micro-mechanical oscillators).