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Precision Measurements: Space-Time and Environmental Sensing

Phys-X activities in precision measurements are broad-reaching and span many subfields leveraging a variety of methods of experimental physics (optics, imaging, lasers, spectroscopy, quantum, atomic and molecular science and sensors). These are typically methods and instruments that make precise physical measurements (e.g. measuring small forces with light), but also encompass tools used in chemistry and biology. Precision measurements at fundamental limits are required for probing new science and enable applications that include:

“Position and Time” – the basic aspects of our everyday lives - are fundamental concepts of physics inseparably interconnected by Einstein’s Theory of Relativity and affected by mass and gravity.  The concepts of space and time are key to our understanding of the universe and to our technological advancement.  Understanding the space-time and gravity holds the key to unraveling the mysteries of “dark matter” and “dark energy” that comprise most of our universe.  

Advanced Position Navigation and Time (PNT) systems ultimately rely upon precise Time derived from quantum transitions in simple atoms and upon Position information derived from the constant speed of light, e.g. microwaves and radio frequency (RF).  Research on PNT at Stanford spans from the fundamental atomic physics related to atomic clocks and atom-interferometric inertial sensors, GPS-GNSS science and technology, government policy related to PNT, and information security for critical navigation systems.  PNT applications are ubiquitous and essential for modern technology: phones, cars, planes, financial systems, communication networks, information security, geosciences and environmental monitoring, city planning and infrastructure, animal population monitoring and agriculture, crime prevention, and many others.  It is difficult to overstate the impact of PNT on our modern world and economy, and Stanford can play a key role in the future of PNT.

Precision spectroscopy (both optical and microwave) of quantum atomic and molecular systems provide the foundations and the basic units for measurements of time and space.
Advanced methods of laser spectroscopy include laser-cooling and manipulation of the motional degrees of freedom of atoms combined with coherent-control of quantum states. These precision measurements enable deeper understanding of the underlying science and development of the next generation of atomic clocks, atomic inertial sensors, and atomic magnetometers.
A key synergism for this research area within Phys-X is with the Stanford Center for Position Navigation and Time (SCPNT) that brings together faculty from Physics and Engineering (Aero Astro, EE, ME), with broader contacts to Computer Science, SLAC, and Earth Sciences.

Environmental Sensing
Precise physical measurements enable new capabilities to address key questions in a very complex field of the environment. Methods such as precision laser spectroscopy of quantum states of molecules can provide critical information about gas concentration as well as chemical reactivity, temperature, and pressure.  Of particular interest are quantitative measurements of greenhouse gases (GHG) and reactive and hazardous species (e.g. CH4, CO, SO2, NOx, etc.).  The interconnected environment and energy systems are multidimensional; addressing challenges in these areas requires input and coordination across multiple fields of science.  PHYS-X brings to those topics special expertise in measurement science, mathematical modeling, and development of novel techniques and instrumentation to provide crucial quantitative data on trace atmospheric constituents and their dynamics.  Improvements in the accuracy, reliability, and cost-effectiveness of the measurement technology is essential for obtaining data to be incorporated into atmospheric models for predicting future environmental scenarios stemming from global warming, air pollution, and climate change.

A new and rapidly growing program within PHYS-X is involved in a regionally-based Global Environment and Measurement Monitoring Network (GEMM) addressing California regional environmental challenges, for example, urban air pollution, fresh water resources and supply issues, and the threat to coastal areas of sea level rise.  The objective of the GEMM initiative is to bring together the development of measurement science tools, monitoring capabilities, analytical modeling, and economic analysis for informed government policy decision making and the establishment of effective adaptation and mitigation policies.

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