1 (Almost) Absolute Zero Parkland Middle School 9 January 2008 William D. Phillips Laser cooling and trapping group National Institute of Standards and Technology Gaithersburg, Maryland USA and The Joint Quantum Institute: NIST and the University of Maryland The Science of Cold

2 NIST is one of the most important laboratories in the world for research on getting to the coldest possible temperatures. NIST and Absolute Zero

3 NIST is one of the most important laboratories in the world for research on getting to the coldest possible temperatures. NIST and Absolute Zero Why?

4 Luis Luis Orozco is Professor of Physics at the University of Maryland and a researcher with the Joint Quantum Institute, a collaboration between the university and NIST dedicated to the goals of controlling and exploiting quantum systems. “...if we have cold atoms and they're moving very, very slowly, then I should be able to learn a lot and get information out of those atoms.” --from a PBS interview about Absolute Zero

5 What does NIST do? Among other responsibilities, the National Institute of Standards and Technology is the keeper of the the standards of measurements for the United States. length time mass Images Copyright Shutterstock

6 It’s about TIME! Why does NIST care about making things cold? When Einstein asked himself “What is time?”, he answered: “Time is what a clock measures.” (but what IS “time”?) Images Copyright Shutterstock

7 How do clocks measure time? Different clocks have different “tickers.” Images Copyright Shutterstock

8 The best clocks are atomic clocks: the atoms are the tickers quartz crystal tuning fork (the ticker of a quartz watch) Artist’s cartoon of an atom The crystal vibrates at a specific frequency, each one a little different. Atoms also “vibrate” at specific frequencies; all atoms of the same type are perfectly identical. Image John Vig Image Copyright Shutterstock

9 My goodness, it’s 12:15: Time for lunch Time for lunch

10 Who cares? GPS satellite. One reason we need atomic clocks is the Global Positioning System. Atomic clocks in satellites guide cars, planes, backpackers, and military vehicles. For improved navigation, communication, scientific research, and national security, we are always trying to improve atomic clocks, but we hit a snag because the atoms move so fast. Image Copyright Shutterstock Image NASA

11 Atoms in a gas are moving really fast, and that makes it hard to measure their ticking. Fast gas atoms make a fast atomic beam. about 200 meters/sec

12 COLD: slow atoms HOT: fast atoms Hot and Cold

13 Demonstrations

14 The Absolute or “Kelvin” temperature scale 0 K => absolute zero 300 K => room temperature

15 The Absolute or “Kelvin” temperature scale 300 K => room temperature 273 K => ice melts 0 K => absolute zero

16 The Absolute or “Kelvin” temperature scale 0 K => absolute zero 300 K => room temperature 195 K => dry ice 273 K => ice melts

17 The Absolute or “Kelvin” temperature scale 0 K => absolute zero 300 K => room temperature 195 K => dry ice 273 K => ice melts 185 K => a cold day in Antarctica

18 The Absolute or “Kelvin” temperature scale 0 K => absolute zero 300 K => room temperature 195 K => dry ice 77 K => liquid nitrogen 273 K => ice melts 185 K => a cold day in Antarctica

19 pull out balloons

20 How do we cool something without touching it? condensation

21 Halley’s comet

22 Halley’s comet We use radiation pressure to push on atoms and make them slow down.

23 Na Optical Molasses How cold are these atoms?

24 The Absolute or “Kelvin” temperature scale 0 K => Absolute Zero 300 K => room temperature 195 K => dry ice 77 K => liquid nitrogen 273 K => ice melts 185 K => a cold day in Antarctica

25 The Absolute or “Kelvin” temperature scale 0 K => Absolute Zero 300 K => room temperature 195 K => dry ice 77 K => liquid nitrogen 3 K => outer space 273 K => ice melts 185 K => a cold day in Antarctica

26 T = 700 nK! This is 100 million times colder than liquid nitrogen, about 4 million times colder than the temperature of outer space. By measuring the velocity of the atoms, we could determine the temperature of laser-cooled atoms. By 1995, we had cooled a gas of cesium atoms to: What sort of clock can we make with atoms this cold? The thermal velocity of these atoms is V thermal < 1 cm/s This was about 200 time COLDER than everybody thought was possible!

27 NIST F-1 Copyright Geoffrey Wheeler

28 Today’s laser cooled clocks are the most accurate primary time standards ever made: better than one second in 60 million years ! laser cooled clock performance But other scientists at NIST have gotten even colder than my team was able to get with laser cooling. Eric Cornell and his team started with laser cooling and then used evaporation. But what do we use for a container? No material vessel, hot or cold, will do. We use a magnetic bottle. Einstein drawing by Bülent Atalay

29 trapping

30 From next week’s NOVA program, let’s listen to Eric Cornell tell about the coldest gas ever made, a new state of matter, which won him and his colleagues the 2001 Nobel Prize in Physics Eric Cornell clip intro

K 100 K 1 K K K K K K K surface of the sun: 5000 K room temperature: 300 K outer space: 3 K liquid nitrogen: 77 K laser cooling: 0.7  K Bose-Einstein Condensation: 1 nK BEC in space (the future):1 pK log thermometer logarithmic thermometer

32 What’s Next? Better clocks Tests of the fundamental understanding of Nature Quantum Computers More...

33 The End