Quantum Rotation Sensing with Dual Sagnac Interferometers in an Atom-Optical Waveguide

We describe a Sagnac interferometer suitable for rotation sensing, implemented using an atomic Bose-Einstein condensate confined in a harmonic magnetic trap. The atom wave packets are split and recombined by standing-wave Bragg lasers, and the trapping potential steers the packets along circular trajectories with a radius of 0.2 mm. Two conjugate interferometers are implemented simultaneously to provide common-mode rejection of noise and to isolate the rotation signal. With interference visibilities of about 50%, we achieve a rotation sensitivity comparable to Earth's rate in about 10 min of operation. Gyroscope operation was demonstrated by rotating the optical table on which the experiment was performed.

A cylindrically symmetric magnetic trap for compact Bose-Einstein condensate atom interferometer gyroscopes

We present a variant of the time-orbiting potential trap suitable for Bose-Einstein condensate atom interferometers, which provides weak, cylindrically symmetric confinement as well as support for the atoms against gravity. This trapping configuration is well-suited for the implementation of a compact atom interferometer based gyroscope. The trap is made up of six coils, which were produced using photolithographic techniques and take up a modest volume of approximately 1 cubic inch inside a vacuum chamber. The trapping frequencies and thermal characteristics of the trap are presented, showing cylindrical symmetry and scalability of the trapping frequencies from 1 Hz to 8 Hz in the symmetry plane.

Fast phase stabilization of a low frequency beat note for atom interferometry

Atom interferometry experiments rely on the ability to obtain a stable signal that corresponds to an atomic phase. For interferometers that use laser beams to manipulate the atoms, noise in the lasers can lead to errors in the atomic measurement. In particular, it is often necessary to actively stabilize the optical phase between two frequency components of the beams. Typically this is achieved using a time-domain measurement of a beat note between the two frequencies. This becomes challenging when the frequency difference is small and the phase measurement must be made quickly. The method presented here instead uses a spatial interference detection to rapidly measure the optical phase for arbitrary frequency differences. A feedback system operating at a bandwidth of about 10 MHz could then correct the phase in about 3 μs. This time is short enough that the phase correction could be applied at the start of a laser pulse without appreciably degrading the fidelity of the atom interferometer operation. The phase stabilization system was demonstrated in a simple atom interferometer measurement of the (87)Rb recoil frequency.

Effect of back support and stethoscope head on seated blood pressure determinations

Seated BP measurements were taken in 48 men with a history of essential hypertension: in a chair with back support v on an examining table with no back support, and with bell v diaphragm stethoscope head in each condition. There were no significant differences between bell and diaphragm in SBP or DBP determinations. SBP was not significantly different between table and chair, but table DBP was 6.5 mm Hg higher (P less than .0001) than chair DBP. We conclude that back support, but not bell v diaphragm stethoscope head, affects seated BP determinations.

A study of telephone advice in managing out-of-hours calls

Two doctors in a five-partner urban practice recorded details of their out-of-hours telephone calls for a year. No caller was refused a visit, but 474 of the 809 incoming calls (59%) were managed by telephone advice, an unexpectedly high proportion. Although these callers were instructed to telephone again if still worried, only 40 did so during the same duty period, and only 55% of a smaller sample of patients receiving telephone advice only consulted again within a week. No evident detriment to patients' health was observed. Thirty nine (5%) of the 809 incoming calls were managed by an out-of-hours surgery attendance and 296(37%) by a home visit. The urgency of the visits made was categorized retrospectively as high (34% of visits), medium (39%) and low (27%). It is hoped that this descriptive account will foster discussion of the value and implications of telephone advice in managing out-of-hours calls.