In most atomic physics systems, detection of the atom’s state is accomplished with resonance fluorescence using macroscopic equipment such as bulk lenses and commercial single-photon detectors, both placed outside the vacuum chamber. Integrated Single-Photon Avalanche Detectors (SPADs) Our collaborators at NIST have shown that the multi-ensemble interrogation approach can give an exponential improvement to clock stability.

This allows us to use more advanced clock-interrogation schemes (multi-ensemble interrogation) that can offer dramatic improvements to the overall clock performance. Because of the precision and scalability of the fabrication process, we can individually trap, address, and detect 10’s to 100’s of ions. An ion trap platform is not only well suited for confining individual atomic ions, but it can also provide the platform and the photonics that are required to deliver light to control the ions and the detectors for state readout. Probing the optical frequencies of atoms requires precise localization of the atoms and precise control and measurement of their electronic state. The individual addressability and readout of the atoms is a key capability that allows us to significantly reduce resource and size requirements for our transportable optical atomic clock. The microfabricated surface ion-traps developed at Sandia offer an ideal platform for transportable optical atomic clocks: photonics integrated directly in the surface trap can control and deliver light precisely to each atom and single-photon detectors can be fabricated directly under each atom for individual readout. TICTOC will take advantage of novel atomic interrogation protocols on ensembles of individually localized atomic ions. This is one of the key goals of DARPA’s A-PhI program, which funds our project named Trapped Ion Clock with photonic Technologies on Chip (TICTOC). The precision of an optical atomic-clock is required to meet the timing needs, however scaling down the bulky laboratory infrastructure required to control the atoms poses significant challenges.

Providing a local and transportable timing source will give redundancy to GPS in the event of a service outage. Currently, PNT resources are primarily provided by the Global Position System (GPS), however recent technology has made GPS vulnerable to disruption. Position, Navigation, and Timing (PNT) are critical capabilities to DoD missions as well as for many civilian applications. The inset image details the various waveguide output couplers at a particular trap location. Light is coupled into the device through the diagonally placed input couplers seen near the corners of the trap. The three rows of ion trap locations can support up to 24 ions, each in their own potential well. Figure 1: Surface ion trap used to demonstrate integrated waveguide trapping. A miniature, highly mobile optical atomic clock enabled by integrated single-photon detectors and waveguide light delivery.

Darpa program aims to atomic clocks