Atomic Sensing and Quantum Metrology
In the Cavity QED experiment, we explore the interactions between atoms and photons in the context of quantum metrology. More specifically, we trap and entangle atoms in a high finesse cavity in order to create an atomic spin-squeezed state. The creation of such a state has great potential to improve the precision of all sensors that use atomic clock states by suppressing their atomic projection noise. Sensors that use atomic clock states include atomic clocks, gravimeters, gravity gradiometers, accelerometers and gyroscopes. The improvement of these sensors is important as they have a wide variety of applications such as in inertial navigation systems (INS), oil and mineral exploration, gravitational wave detection and global positioning systems (GPS).
Fluorescence Imaging
The primary readout method for the experiment is measuring the light reflected off of the cavity which contains the sensor atoms. In order to read out the atomic state after the atoms have left the cavity, we use fluorescence imaging to count the number of atoms in each quantum state.
This imaging system is capable of resolving noise smaller than the standard quantum limit. This technique is capable of reaching a clock accuracy in 3 times less averaging time than comparable free-space atomic clocks.
Image: Fluorescence of the two quantum states.
Atom Interferometry with Nonlocal Entanglement
Atomic sensors which utilize spin-squeezed states contain localized collections of entangled atoms. For spatially distributed networks of sensors with only local entanglement at each node, the noise performance of the network improves at best with square root of the number of nodes. We demonstrated that nonlocal entanglement between network nodes offers better scaling with network size.
A network of four atomic clocks provides up to 1.7 times better precision than one without nonlocal entanglement, and 3.8 times improvement as compared to a network of sensors operating at the quantum projection noise limit.
Image: Diagram of a differential gravitational sensor's operating principle.