Holding in Suspense

Philip Ball

Tianliang Yan, J. Smetana, Artemiy V. Dmitriev +2 more

We present our development of a table-top quantum sensor with femtometer sensitivity within the acoustic frequency band. Our sensor utilises the expertise developed within the gravitational-wave community, particularly in the control of high-finesse, suspended interferometers, and the mitigation of seismic and thermal noise. We construct a system consisting of a cryostat-mounted four-stage suspension supporting two cavities with optical finesse in excess of 350,000. We use active isolation of the entire cryostat system to achieve an order-of-magnitude of reduction of the seismic noise prior to the passive isolation of the internal suspension. We achieve the femtometer sensitivity using a custom-made phase lock loop. With further enhancements to the readout electronics and suspension characteristics, we aim to reach the quantum radiation pressure noise. This sensor holds the potential for future applications in demonstrating macroscopic entanglement and testing semi-classical and quantum gravity theories.

K. J. Hughes, John H. Burke, Charles A. Sackett

Atoms from a (87)Rb condensate are suspended against gravity using repeated reflections from a pulsed optical standing wave. Up to 100 reflections are observed, yielding suspension times of over 100 ms. The local gravitational acceleration can be determined from the pulse rate required to achieve suspension. Further, a gravitationally sensitive atom interferometer was implemented using the suspended atoms. This technique could potentially provide a precision measurement of gravity without requiring the atoms to fall a large distance.

Bernard d’Espagnat

Daniel N. Rogovin, P. McGrath

We examine phase conjugation in liquid suspensions of microparticles in the saturation limit. If the polarizations of the pump waves are orthogonal, new states should appear discontinuously in a pairwise fashion which are stable at the bifurcation point. These states correspond to different intensities of the conjugate and amplified probe waves. Analysis indicates that this effect should be experimentally accessible in the microwave region utilizing 10-\ensuremath{\mu}m microspheres.

Bernard d’Espagnat