Quantum Optics Seminar by Farit Khalili

 Engineering the effective "negative evolution" of atomic spin systems

The modern laser gravitational wave detectors (GWDs) have reached such a level of sensitivity that further improvement requires quantum-noise-evading techniques. Several proposals to this end have been discussed in the literature, e.g. use of an additional long (and therefore expensive) filter cavities or replacing the current Michelson interferometer topology by that of the quantum speedmeter.

The very promising way to suppress the quantum noise is to link the interferometer to a negative-mass spin system via entangled light. This approach does not require modifications to the highly refined core optics of the present GWD design. However, within this approach, the Larmor frequency of the atomic spin system has to match the very low (about 1Hz) pendulum eigenfrequency of the GWDs suspended mirrors. Here, we discuss two possible ways to overcome this disadvantage: (i) matching the effective susceptibilities of the interferometer and spin system using the virtual rigidity concept and (ii) modification of the spin system dynamics using the optical spring effect.