Cold Core Technology Platform

Summary

We are building a cold-atom based sensor program that represents a new approach to metrology—to establish a set of chip-scale tools that enable real-world use of cold trapped atoms as absolute sensors. Our "Cold Core Technology" (CCT) platform is focused on translational research into miniaturized cold-atom technology with unique atomic species and the integration photonic elements like gratings, metasurfaces, and waveguides. This combination of research thrusts enables robust devices for the measurement of many different physical quantities, including vacuum, acceleration, rotation, magnetic fields, electric fields, and even blackbody radiation.

Description

Figure 1: A background molecule ejects a cold atom from a trap.

Credit: Curt Suplee

Cold atoms can be useful sensors for a host of different phenomena including inertial forces like acceleration and rotation, gravity, magnetic fields, vacuum and time. However, most of these applications are still confined to the laboratory. Building robust, field-deployable quantum sensors made with cold atoms has proven elusive, primarily because of the complexity of the devices needed to create and control these exotic gasses. These apparatuses generally require several lasers, hundreds of optics, and exquisite control of external magnetic and electric fields.

The CCT program is designed to meet this challenge by integrating state-of-the-art photonic elements with cold atoms. Photonics has the power to greatly simplify the optical setups needed by cold atoms, by reducing the number of input laser beams or number of bulk optics dramatically. Nanophotonic elements offer unique capabilities such as strong atom-photon coupling that can be leveraged to make new atom devices for metrology and quantum science. Our program seeks to systematically engineer the integration of cold atoms and photonics using new software tools and state-of-the-art fabrication techniques to enable the next generation of cold-atom-based metrology.

Our devices generally use atomic species other than rubidium, which is the standard workhorse in atomic physics. While rubidium is useful for many measurements, other species like lithium are potentially better for measuring vacuum, for example. Strontium is better for atomic clocks and potentially advantageous for inertial sensing. Molecules (see the related PRIME project) can be useful for measuring temperature. Understanding how to build devices using such different species requires new understanding of how their complex structures may affect the performance of miniaturized laser cooling devices.

Our first, flagship device is the Cold Atom Vacuum Standard (CAVS). In our purpose-designed trap, a collision between a background molecule and a trapped Li atom will result in the atom being knocked out of the trap with near unit probability, as illustrated in Figure 1. We will exploit this to make an absolute sensor of number density—CAVS will count background molecules in the vacuum by measuring the lifetime of the cold atom trap.

Figure 2: Grating MOT chip for first generation p-CAVS.

Credit: Curt Suplee

The CAVS is a laboratory-size standard, but our program seeks to make it become a replacement for the ionization gauge by leveraging photonics to shrink it into a manageable package. This portable version of the CAVS, the p-CAVS, is currently under development. At its heart is a photonic grating chip that takes a single input beam and makes three more necessary for trapping atoms (Figure 2). In addition, our chip has an atomic aperture behind which we can place our specially designed alkali source. The aperture allows the input beam to pass and interact with the atoms from the source for longer, pre-slowing atoms that would otherwise never be trapped. This key innovation allows us to trap Li atoms, an ideal sensor atom for vacuum.

The next generation of cold-atom based sensors promises a revolution in metrology, impacting the measurement of acceleration, rotation, magnetic fields, electric fields, blackbody radiation, temperature, vacuum and even time. Our focus is to bring these technologies to the real world, building up this new measurement future with cold atoms.

Major Accomplishments

• Realization of a new, 3D printed alkali vapor source (2018).
• Realization of the first grating MOT of Li (2019).
• Construction of the prototype p-CAVS (2020).
• Production of the first grating MOT of an alkaline-earth metal, Sr (2020).