Research

Talk to a modern-day physicist and you may hear the term "precision cosmology" bandied about as a reference to the fact that measurements of various aspects of our universe are now achieving sub-percent precision. This is indeed the case and cause for celebration, but the study of the cosmos is anything but a mop-up job. Yes, we have come to understand quite a lot about our universe and its evolution since the Big Bang; its age, the relative breakdown of its contents, and how inhomogeneities evolved over time to produce the web of cosmic structure we see today. But many looming questions remain still. 95% of the energy content of the universe is in the form of dark energy and dark matter: what are the particle constitutents of these forms of energy? How will the nature of dark energy influence the long-term future of the universe? How did the Big Bang begin - was cosmic inflation involved, or something more exotic?

Cosmological questions aside, our newfound abilities to precisely measure the cosmos are enabling us to use the universe itself as a laboratory for high energy physics. By measuring the properties of the early universe, we can access energy scales that would otherwise require a particle accelerator the diameter of the solar system. Through these endeavors we hope to constrain extensions to and generalizations of the Standard Model of particle physics, up to and including Grand Unified Theories and possibly even features of quantum gravity.

One of the most valuable tools we have for studying the universe is the cosmic microwave background (CMB) - the relic thermal radiation that decoupled from the primordial plasma when the universe was just 0.003% of its current age. As a snapshot of the very early universe, it can tell us about the physical processes relevant at high energies and early cosmic times. Separately, since the CMB photons we see now have traveled over 13.7 billion years of cosmic history on their way to us, they form a "backlight" to all intervening matter and energy and allow us to probe physical processes that affect the growth of cosmic structure.

Since its discovery half a century ago, measurements of the CMB have arguably been the most important inputs to our current cosmological model, and they are "the gift that keeps on giving." With more precise measurements made by more sensitive observatories, we expect to be able to answer a host of scientific questions in the fields of cosmology, particle physics, and astrophysics. These observatories are designed to be sensitive to wavelengths on the order of a millimeter, and usually take the form of telescopes in dry, high-altitude environments like the Atacama desert or the geographic South Pole. As funding allows, sometimes we also launch telescopes on satellites or high-altitude balloons to escape the pesky effects of the atmosphere.  Our group's current focus is on the Simons Observatory - a new experiment coming online now in the Chilean Atacama desert, which includes multiple telescopes making coordinated observations over a range of angular sensitivities and wavelengths.

Measurements of the microwave sky are fundamentally limited by counting statistics of the incoming photons, so upcoming CMB observatories need to incorporate increasingly large arrays of superconducting sensors - already numbering in the tens of thousands. While these sensors themselves are highly scalable, the supporting electronics required to read them out are less so; a sub-focus of our group has been to improve this situtation by developing and deploying highly multiplexed readout technologies. These technologies are also useful for non-CMB experiments that use similar types of detectors, and we are also working to apply them to  other physics experiments like those searching for dark matter.

Current Projects

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Past Projects

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