An Atomic Gravitational Wave Interferometric Sensor (AGIS)

Abstract

We propose two distinct atom interferometer gravitational wave detectors, one terrestrial and another satellite-based, utilizing the core technology of the Stanford 10 m atom interferometer presently under construction. Each configuration compares two widely separated atom interferometers run using common lasers. The signal scales with the distance between the interferometers, which can be large since only the light travels over this distance, not the atoms. The terrestrial experiment with baseline ~1 km can operate with strain sensitivity ~10^(-19) / Hz^(1/2) in the 1 Hz - 10 Hz band, inaccessible to LIGO, and can detect gravitational waves from solar mass binaries out to megaparsec distances. The satellite experiment with baseline ~1000 km can probe the same frequency spectrum as LISA with comparable strain sensitivity ~10^(-20) / Hz^(1/2). The use of ballistic atoms (instead of mirrors) as inertial test masses improves systematics coming from vibrations, acceleration noise, and significantly reduces spacecraft control requirements. We analyze the backgrounds in this configuration and discuss methods for controlling them to the required levels.

Figures (17)

• Figure 1: A space-time diagram of a light pulse atom interferometer. The black lines indicate the motion of a single atom. Laser light used to manipulate the atom is incident from above (light gray) and below (dark gray) and travels along null geodesics. The finite speed of the light has been exaggerated.
• Figure 2: (Color online) Figure \ref{['Fig:Raman']} shows an energy level diagram for a stimulated Raman transition between atomic states $\left|1\right>$ and $\left|2\right>$ through a virtual excited state using lasers of frequency $k_1$ and $k_2$. Figure \ref{['Fig:RabiPlot']} shows the probability that the atom is in states $\left|1\right>$ and $\left|2\right>$ in the presence of these lasers as a function of the time the lasers are on. A $\frac{\pi}{2}$ pulse is a beamsplitter since the atom ends up in a superposition of states $\left|1\right>$ and $\left|2\right>$ while a $\pi$ pulse is a mirror since the atom's state is changed completely.
• Figure 3: The atomic energy level diagram for a Bragg process plotted as energy versus momentum. The horizontal lines indicate the states through which the atom is transitioned. By sweeping the laser frequencies the atom can be given a large momentum.
• Figure 4: Figure \ref{['Fig:space-time']} is a space-time diagram of two light pulse interferometers in the proposed differential configuration, as in Figure \ref{['Fig:AI-SingleInterferometer']}. Figure \ref{['Fig:earthsetup']} is a diagram of the proposed setup for a terrestrial experiment. The straight lines represent the path of the atoms in the two $I_L \sim 10$ m interferometers $I_{1}$ and $I_{2}$ separated vertically by $L \sim 1$ km. The wavy lines represent the paths of the lasers.
• Figure 5: A diagram of several clouds of atoms being run through the atom interferometer sequence concurrently. The arrows indicate the velocity of each cloud of atoms at a single instant in time. Earlier shots will be moving with more downward velocity, allowing the clouds to be individually addressed with Doppler detuned laser frequencies.