Travis Horrom

Performance of a prototype atomic clock based on lin‖lin coherent population trapping resonances in Rb atomic vapor

We report on the performance of the first table-top prototype atomic clock based on coherent population trapping (CPT) resonances with parallel linearly polarized optical fields (lin‖lin configuration). Our apparatus uses a vertical-cavity surface-emitting laser (VCSEL) tuned to the D1 line of 87Rb with the current modulation at the 87Rb hyperfine frequency. We demonstrate cancellation of the first-order light shift by the proper choice of rf modulation power and further improve our prototype clock stability by optimizing the parameters of the microwave lock loop. Operating in these optimal conditions, we measured a short-term fractional frequency stability (Allan deviation) 2×10−11τ−1/2 for observation times 1 s ≤ τ ≤ 20 s. This value is limited by large VCSEL phase noise and environmental temperature fluctuation. Further improvements in frequency stability should be possible with an apparatus designed as a dedicated lin‖lin CPT resonance clock with environmental impacts minimized.

Quantum-enhanced magnetometer with low-frequency squeezing

We report the demonstration of a magnetometer with noise-floor reduction below the shot-noise level. This magnetometer, based on a nonlinear magneto-optical rotation effect, is enhanced by the injection of a squeezed vacuum state into its input. The noise spectrum shows squeezed noise reduction of about

Polarization self-rotation in ultracold atomicRb87

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Quadrature noise in light propagating through a cold 87Rb atomic gas

dB spanning from close to 100 Hz to several megahertz. We also report on the observation of two different regimes of operation of such a magnetometer: one in which the detection noise is limited by the quantum noise of the light probe only, and one in which we see additional noise originating from laser noise which is rotated into the vacuum polarization.

All-atomic generation and noise-quadrature filtering of squeezed vacuum in hot Rb vapor

We report on a combined experimental and theoretical study of polarization self-rotation in an ultracold atomic sample. In the experiments, a probe laser is tuned in the spectral vicinity of the D{sub 1} line to observe polarization self-rotation in a sample of ultracold {sup 87}Rb prepared in a magneto-optical trap (MOT). Systematic measurements of the rotation angle of the light-polarization ellipse as a function of laser intensity, initial ellipticity, and detuning are made. The observations, in good agreement with theoretical simulations, are indicative of the presence of a residual static magnetic field, resulting in measured asymmetries in the rotation angle for right and left ellipticities. In this paper we present our detailed experimental results and analysis of the combined influences of polarization self-rotation and the Faraday effect.

All-atomic source of squeezed vacuum with full pulse-shape control

We report on the study of the noise properties of laser light propagating through a cold 87Rb atomic sample held in a magneto-optical trap. The laser is tuned around the F g  = 2 → F e  = 1, 2 D1 transitions of 87Rb. We observe quadrature-dependent noise in the light signal, an indication that it may be possible to produce squeezed states of light. We measure the minimum and maximum phase-dependent noise as a function of detuning and compare these results to theoretical predictions to explore the best conditions for light squeezing using cold atomic Rb.

Slow and stored light with atom-based squeezed light

With our all-atomic squeezing and filtering setup, we demonstrate control over the noise amplitudes and manipulation of the frequency-dependent squeezing angle of a squeezed vacuum quantum state by passing it through an atomic medium with electromagnetically induced transparency (EIT). We generate low sideband frequency squeezed vacuum using the polarization self-rotation effect in a hot Rb vapor cell, and direct it through a second atomic vapor subject to EIT conditions. We use the frequency-dependent absorption of the EIT window to demonstrate an example of squeeze amplitude attenuation and squeeze angle rotation of the quantum noise quadratures of the squeezed probe. These studies have implications for quantum memory and storage as well as gravitational wave interferometric detectors.

Propagation of a squeezed optical field in a medium with superluminal group velocity

We report on the generation of pulses of a low-frequency squeezed vacuum with noise suppression >2 dB below the standard quantum limit in a hot resonant 87Rb vapour with polarization self-rotation. We demonstrate the possibility of precisely controlling the temporal profile of the squeezed noise quadrature by applying a calibrated longitudinal magnetic field, without degrading the maximum amount of squeezing.

Propagation of quantum optical fields under the conditions of multi-photon resonances in a coherent atomic vapor

In this manuscript we present calculations that consider the propagation of a squeezed vacuum signal field through a resonant atomic medium under electromagnetically induced transparency (EIT). We show that squeezing is degraded due to four-wave mixing processes at high optical depth of the atomic medium. We also present some preliminary results for degenerate Zeeman EIT resonances.

All atomic generation and manipulation of squeezed vacuum in hot Rb vapor

We investigated the propagation of a squeezed optical field, generated via the polarization self-rotation effect, with a sinusoidally modulated degree of squeezing through an atomic medium with anomalous dispersion. We observed the advancement of the signal propagating through a resonant Rb vapor compared to the reference signal, propagating in air. The measured advancement time grew linearly with atomic density, reaching a maximum of 11±1  μs, which corresponded to a negative group velocity of v(g)≈-7,000  m/s. We also confirmed that the increasing advancement was accompanied by a reduction of output squeezing levels due to optical losses, in good agreement with theoretical predictions.