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Researchers Develop Blueprint for Nuclear Clock Accurate Over Billions of Years

Wednesday, March 21, 2012

A clock accurate to within a tenth of a second over 14 billion years -- the age of the universe -- is the goal of research being reported this week by scientists from three different institutions. To be published in the journal Physical Review Letters, the research provides the blueprint for a nuclear clock that would get its extreme accuracy from the nucleus of a single thorium ion.

Such a clock could be useful for certain forms of secure communication -- and perhaps of greater interest -- for studying the fundamental theories of physics. A nuclear clock could be as much as one hundred times more accurate than current atomic clocks, which now serve as the basis for the global positioning system (GPS) and a broad range of important measurements.

"If you give people a better clock, they will use it," said Alex Kuzmich, a professor in the School of Physics at the Georgia Institute of Technology and one of the paper's co-authors. "For most applications, the atomic clocks we have are precise enough. But there are other applications where having a better clock would provide a real advantage."

For the full article, please go to this link.

Summary: 

Precision of Nuclear Clock Depends on Single Atom of Thorium

Intro: 

Precision of Nuclear Clock Depends on Single Atom of Thorium

Alumni: 

Researchers Develop Blueprint for Nuclear Clock Accurate Over Billions of Years

Monday, March 19, 2012

A clock accurate to within a tenth of a second over 14 billion years -- the age of the universe -- is the goal of research being reported this week by scientists from three different institutions. To be published in the journal Physical Review Letters, the research provides the blueprint for a nuclear clock that would get its extreme accuracy from the nucleus of a single thorium ion.

Such a clock could be useful for certain forms of secure communication -- and perhaps of greater interest -- for studying the fundamental theories of physics. A nuclear clock could be as much as one hundred times more accurate than current atomic clocks, which now serve as the basis for the global positioning system (GPS) and a broad range of important measurements.

"If you give people a better clock, they will use it," said Alex Kuzmich, a professor in the School of Physics at the Georgia Institute of Technology and one of the paper's co-authors. "For most applications, the atomic clocks we have are precise enough. But there are other applications where having a better clock would provide a real advantage."

In addition to the Georgia Tech physicists, researchers in the School of Physics at the University of New South Wales in Australia and at the Department of Physics at the University of Nevada also contributed to the study. The research has been supported by the Office of Naval Research, the National Science Foundation and the Gordon Godfrey fellowship.

Early clocks used a swinging pendulum to provide the oscillations needed to track time. In modern clocks, quartz crystals provide high-frequency oscillations that act like a tuning fork, replacing the old-fashioned pendulum. Atomic clocks derive their accuracy from laser-induced oscillations of electrons in atoms. However, these electrons can be affected by magnetic and electrical fields, allowing atomic clocks to drift ever so slightly -- about four seconds in the lifetime of the universe.

Because neutrons are much heavier than electrons and densely packed into the atomic nucleus, they are less susceptible to these perturbations than the electrons. A nuclear clock should therefore be less affected by environmental factors than its atomic cousin.

"In our paper, we show that by using lasers to orient the electrons in a very specific way, we can use the neutron of an atomic nucleus as the clock pendulum," said Corey Campbell, a research scientist in the Kuzmich laboratory and the paper's first author. "Because the neutron is held so tightly to the nucleus, its oscillation rate is almost completely unaffected by any external perturbations."

To create the oscillations, the researchers plan to use a laser operating at petahertz frequencies -- 10 (15) oscillations per second -- to boost the nucleus of a thorium 229 ion into a higher energy state. Tuning a laser to create these higher energy states would allow scientists to set its frequency very precisely, and that frequency would be used to keep time instead of the tick of a clock or the swing of a pendulum.

The nuclear clock ion will need to be maintained at a very low temperature -- tens of microkelvins -- to keep it still. To produce and maintain such temperatures, physicists normally use laser cooling. But for this system, that would pose a problem because laser light is also used to create the timekeeping oscillations.

To solve that problem, the researchers include a single thorium 232 ion with the thorium 229 ion that will be used for timekeeping. The heavier ion is affected by a different wavelength than the thorium 229. The researchers can then cool the heavier ion, which lowers the temperature of the clock ion without affecting the oscillations.

"The cooling ion acts as a refrigerator, keeping the clock ion very still," said Alexander Radnaev, a graduate research assistant in the Kuzmich lab. "This is necessary to interrogate the clock ion for very long and to make a very accurate clock that will provide the next level of performance."

Calculations suggest that a nuclear clock could be accurate to 10 (-19), compared to 10 (-17) for the best atomic clock.

Because they operate in slightly different ways, atomic clocks and nuclear clocks could one day be used together to examine differences in physical constants. "Some laws of physics may not be constant in time," Kuzmich said. "Developing better clocks is a good way to study this."

Though the research team believes it has now demonstrated the potential to make a nuclear clock -- which was first proposed in 2003 -- it will still be a while before they can produce a working one.

The major challenge ahead is that the exact frequency of laser emissions needed to excite the thorium nucleus hasn't yet been determined, despite the efforts of many different research groups.

"People have been looking for this for 30 years," Campbell said. "It's worse than looking for a needle in a haystack. It's more like looking for a needle in a million haystacks."

But Kuzmich believes that problem will be solved, allowing physicists to move to the next generation of phenomenally accurate timekeepers.

"Our research shows that building a nuclear clock in this way is both worthwhile and feasible," he said. "We now have the tools and plans needed to move forward in realizing this system."

 

Research News & Publications Office

Georgia Institute of Technology

75 Fifth Street, N.W., Suite 314

Atlanta, Georgia  30308  USA

 

Media Relations Contacts: John Toon (404-894-6986)(jtoon@gatech.edu) or Abby Robinson (404-385-3364)(abby@innovate.gatech.edu).

Writer: John Toon

 

 

 

 

 

 

Media Contact: 

John Toon

Research News & Publications Office

404-894-6986

jtoon@gatech.edu

Summary: 

A clock accurate to within a tenth of a second over 14 billion years – the age of the universe – is the goal of research being reported this week in the journal Physical Review Letters. The research provides the blueprint for a nuclear clock based on a single thorium ion.

Intro: 

A clock accurate to within a tenth of a second over 14 billion years – the age of the universe – is the goal of research being reported this week in the journal Physical Review Letters. The research provides the blueprint for a nuclear clock based on a single thorium ion.

Alumni: 

Physicists receive GT Fire Awards

Monday, March 19, 2012

Two School of Physics faculty have recently received funding from the Georgia Tech Fund for Innovation in Research and Education (GT FIRE). The GT FIRE program was created in order to inspire innovation in research and education at Georgia Tech. “The program is off to a great start,” said Rafael L. Bras, provost and executive vice president for academic affairs. “The submitted proposals mesh well with our strategic plan, and that was our hope.” “Innovation in research is critical for us to lead and set the science, technology and policy agenda for the United States and the world,” said Steve Cross, executive vice president for research. “I am happy to support GT FIRE in stimulating faculty thinking and creativity.”

Dr. Harold Kim received an award for "A single-cell study to investigate the functional impact of chromosomal landscape."  By correlating expression noise of identical genes placed at different locations on the genome, Kim will create a construction of the segregation map of genes inside the nucleus of a cell.  The funds will be used for a pilot study aimed to construct the segregation map of genes inside the nucleus of a cell. Prof. Kim will correlate expression noise of two identical genes placed at various locations on the yeast genome and investigate whether this correlation can be used to infer physical distance inside the nucleus.

Dr. Daniel Goldman received an award for "Micro-Labs: A hands-on course in experiment, theory and computation in Nonlinear Science/Complex Systems."  Using GT FIRE funds, Prof. Goldman will develop a course in Nonlinear Science/Complex Systems which will emphasize and demonstrate the creativity and critical thinking skills involved in scientific inquiry through participation in hands-on “micro-labs.” These will be short and intense laboratory experiences in which creative problem solving and hypothesis generation will be utilized to design and build an experiment, collect and analyze data, and compare data to a model, all in a single week while working in a laboratory with Prof. Goldman and a graduate student TA. The course will show students that original, cutting-edge science is accessible to them now, with skills and tools they already have or, with guidance, can readily develop.

Summary: 

Two School of Physics faculty have recently received funding from the Georgia Tech Fund for Innovation in Research and Education (GT FIRE). The GT FIRE program was created in order to inspire innovation in research and education at Georgia Tech.

Intro: 

Two School of Physics faculty have recently received funding from the Georgia Tech Fund for Innovation in Research and Education (GT FIRE). The GT FIRE program was created in order to inspire innovation in research and education at Georgia Tech.

Alumni: 

Physics Faculty Awarded Promotion and Tenure

Thursday, March 15, 2012

Congratulations to Physics faculty Mike Schatz, Markus Kindermann and Joshua Weitz, who have been granted promotions at Georgia Tech.  Dr. Schatz was promoted to the rank of professor, and Dr. Kindermann and Dr. Weitz to the rank of associate professor with tenure.

Summary: 

Physics Faculty Awarded Promotion and Tenure

Intro: 

Physics Faculty Awarded Promotion and Tenure

Alumni: 

Physics Alumnus Wins 2012 Sigma Xi Best Thesis Award

Wednesday, March 14, 2012

School of Physics PhD alumnus and current postdoc Chen Li is a recipient of the 2012 Sigma-Xi Best PhD thesis Award.

Li defended his thesis, "Biological, Robotic, and Physics Studies to Discover Principles of Legged Locomotion on Granular Media", in November and graduated in December (advisor: Daniel Goldman). In July, he will join Prof. Robert Full's Poly-PEDAL Lab at UC Berkeley as a Miller Fellow.

Congratulations!

Summary: 

School of Physics PhD alumnus and current postdoc Chen Li is a recipient of the 2012 Sigma-Xi Best PhD thesis Award

Intro: 

School of Physics PhD alumnus and current postdoc Chen Li is a recipient of the 2012 Sigma-Xi Best PhD thesis Award

Alumni: 

Scientists Score Another Victory Over Uncertainty in Quantum Physics Measurements

Sunday, February 26, 2012

Most people attempt to reduce the little uncertainties of life by carrying umbrellas on cloudy days, purchasing automobile insurance or hiring inspectors to evaluate homes they might consider purchasing. For scientists, reducing uncertainty is a no less important goal, though in the weird realm of quantum physics, the term has a more specific meaning.

For scientists working in quantum physics, the Heisenberg Uncertainty Principle says that measurements of properties such as the momentum of an object and its exact position cannot be simultaneously specified with arbitrary accuracy. As a result, there must be some uncertainty in either the exact position of the object, or its exact momentum. The amount of uncertainty can be determined, and is often represented graphically by a circle showing the area within which the measurement actually lies.

Over the past few decades, scientists have learned to cheat a bit on the Uncertainty Principle through a process called “squeezing,” which has the effect of changing how the uncertainty is shown graphically. Changing the circle to an ellipse and ultimately to almost a line allows one component of the complementary measurements – the momentum or the position, in the case of an object – to be specified more precisely than would otherwise be possible. The actual area of uncertainty remains unchanged, but is represented by a different shape that serves to improve accuracy in measuring one property.

This squeezing has been done in measuring properties of photons and atoms, and can be important to certain high-precision measurements needed by atomic clocks and the magnetometers used to create magnetic resonance imaging views of structures deep inside the body. For the military, squeezing more accuracy could improve the detection of enemy submarines attempting to hide underwater or improve the accuracy of atom-based inertial guidance instruments.

Now physicists at the Georgia Institute of Technology have added another measurement to the list of those that can be squeezed. In a paper appearing online February 26 in the journal Nature Physics, they report squeezing a property called the nematic tensor, which is used to describe the rubidium atoms in Bose-Einstein Condensates, a unique form of matter in which all atoms have the same quantum state. The research was sponsored by the National Science Foundation (NSF).

“What is new about our work is that we have probably achieved the highest level of atom squeezing reported so far, and the more squeezing you get, the better,” said Michael Chapman, a professor in Georgia Tech’s School of Physics. “We are also squeezing something other than what people have squeezed before.”

Scientists have been squeezing the spin states of atoms for 15 years, but only for atoms that have just two relevant quantum states – known as spin ½ systems. In collections of those atoms, the spin states of the individual atoms can be added together to get a collective angular momentum that describes the entire system of atoms.

In the Bose-Einstein condensate atoms being studied by Chapman’s group, the atoms have three quantum states, and their collective spin totals zero – not very helpful for describing systems. So Chapman and graduate students Chris Hamley, Corey Gerving, Thai Hoang and Eva Bookjans learned to squeeze a more complex measure that describes their system of spin 1 atoms: nematic tensor, also known as quadrupole.

Nematicity is a measure of alignment that is important in describing liquid crystals, exotic magnetic materials and some high temperature superconductors.

“We don’t have a spin vector pointing in a particular direction, but there is still some residual information in where this collection of atoms is pointing,” Chapman explained. “That next higher-order description is the quadrupole, or nematic tensor. Squeezing this actually works quite well, and we get a large degree of improvement, so we think it is relatively promising.”

Experimentally, the squeezing is created by entangling some of the atoms, which takes away their independence. Chapman’s group accomplishes this by colliding atoms in their ensemble of some 40,000 rubidium atoms.

“After they collide, the state of one atom is connected to that of the other atom, so they have been entangled in that way,” he said. “This entanglement creates the squeezing.”

Reducing uncertainty in measuring atoms could have important implications for precise magnetic measurements. The next step will be to determine experimentally if the technique can improve the measurement of magnetic field, which could have important applications.

“In principle, this should be a straightforward experiment, but it turns out that the biggest challenge is that magnetic fields in the laboratory fluctuate due to environmental factors such as the effects of devices such as computer monitors,” Chapman said. “If we had a noiseless laboratory, we could measure the magnetic field both with and without squeezed states to demonstrate the enhanced precision. But in our current lab environment, our measurements would be affected by outside noise, not the limitations of the atomic sensors we are using.”

The new squeezed property could also have application to quantum information systems, which can store information in the spin of atoms and their nematic tensor.

“There are a lot of things you can do with quantum entanglement, and improving the accuracy of measurements is one of them,” Chapman added. “We still have to obey Heisenberg’s Uncertainty Principle, but we do have the ability to manipulate it.”

Research News & Publications Office
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 314
Atlanta, Georgia  30308  USA

Media Relations Contacts: John Toon (404-894-6986)(jtoon@gatech.edu) or Abby Robinson (404-385-3364)(abby@innovate.gatech.edu)

Writer: John Toon

Media Contact: 

John Toon

Research News & Publications Office

404-894-6986

jtoon@gatech.edu

Summary: 

Uncertainty affects the accuracy with which measurements can be made in quantum physics. To reduce this uncertainty, physicists have learned to "squeeze" certain measurements. Researchers are now reporting a new type of measurement that can be squeezed to improve precision.

Intro: 

Uncertainty affects the accuracy with which measurements can be made in quantum physics. To reduce this uncertainty, physicists have learned to "squeeze" certain measurements. Researchers are now reporting a new type of measurement that can be squeezed to improve precision.

Alumni: 

Dr. Constantine Yannouleas awarded as 2012 APS Outstanding Referee

Thursday, February 16, 2012

Congratulations to Senior Research Scientist Dr. Constantine Yannouleas, who has been awarded as a 2012 APS Outstanding Referee. 

A research scientist with the School of Physics and the Center for Computational Materials Science at Georgia Tech since 1992, he will be attending the  recognition ceremony at the 2012 APS March meeting in Boston, MA.

Summary: 

Dr. Constantine Yannouleas awarded as 2012 APS Outstanding Referee

Intro: 

Dr. Constantine Yannouleas awarded as 2012 APS Outstanding Referee

Alumni: 

$8.5 Million Research Initiative Will Study Best Approaches for Quantum Memories

Thursday, February 16, 2012
$8.5 Million Research Initiative Will Study Best Approaches for Quantum Memories

The U.S. Air Force Office of Scientific Research (AFOSR) has awarded $8.5 million to a consortium of seven U.S. universities that will work together to determine the best approach for generating quantum memories based on interaction between light and matter.  

The team will consider three different approaches for creating entangled quantum memories that could facilitate the long-distance transmission of secure information. The five-year Multidisciplinary University Research Initiative (MURI) will be led by the Georgia Institute of Technology and include scientists from Columbia University, Harvard University, the Massachusetts Institute of Technology, the University of Michigan, Stanford University and the University of Wisconsin.

“We want to develop a set of novel and powerful approaches to quantum networking,” said Alex Kuzmich, a professor in Georgia Tech’s School of Physics and the MURI’s principal investigator.  “The three basic capabilities will be (1) storing quantum information for longer periods of time, on the order of seconds, (2) converting the information to light, and (3) transmitting the information over long distances. We aim to create large-scale systems that use entanglement for quantum communication and potentially also quantum computing.”

For the full article, please visit: http://www.gatech.edu/newsroom/release.html?nid=109721

Summary: 

$8.5 Million Research Initiative Will Study Best Approaches for Quantum Memories

Intro: 

$8.5 Million Research Initiative Will Study Best Approaches for Quantum Memories

Alumni: 

$8.5 Million Research Initiative Will Study Best Approaches for Quantum Memories

Wednesday, February 15, 2012

The U.S. Air Force Office of Scientific Research (AFOSR) has awarded $8.5 million to a consortium of seven U.S. universities that will work together to determine the best approach for generating quantum memories based on interaction between light and matter.  

The team will consider three different approaches for creating entangled quantum memories that could facilitate the long-distance transmission of secure information. The five-year Multidisciplinary University Research Initiative (MURI) will be led by the Georgia Institute of Technology and include scientists from Columbia University, Harvard University, the Massachusetts Institute of Technology, the University of Michigan, Stanford University and the University of Wisconsin.

“We want to develop a set of novel and powerful approaches to quantum networking,” said Alex Kuzmich, a professor in Georgia Tech’s School of Physics and the MURI’s principal investigator.  “The three basic capabilities will be (1) storing quantum information for longer periods of time, on the order of seconds, (2) converting the information to light, and (3) transmitting the information over long distances. We aim to create large-scale systems that use entanglement for quantum communication and potentially also quantum computing.”

The MURI scientists will study three different physical platforms for designing the matter-light interaction used to generate the entangled photons.  These include neutral atom memories with electronically-excited Rydberg-level interactions, nitrogen-vacancy (NV) defect centers in diamonds, and charged quantum dots.

“A large body of work has been initiated in this area over the past 15 years by our team members and their research groups,” Kuzmich noted. “The physical approaches are different, but the goals are closely related, so there are significant opportunities for synergistic activities. Through this MURI, we will be able to interact more closely, communicate more quickly and provide new opportunities for our students and postdoctoral fellows.”

Overall, the MURI has four major goals:

  • To implement efficient light-matter interfaces using three different approaches to entanglement;
  • To realize entanglement lifetimes of more than one second in both the nitrogen-vacancy centers and atomic quantum memories;
  • To implement two-qubit quantum states within memory nodes;
  • To integrate different components and physical implementations into small units capable of significant quantum processing tasks.

Quantum memories generated from the interaction of neutral atoms and light now have maximum lifetimes of approximately 200 milliseconds.  But improvements beyond memory lifetime will be needed before practical systems can be created.

“We aim to be able to combine systems, so that instead of just one memory entangled with one photon, perhaps we could have four of them,” Kuzmich added.  “This may look like a straightforward thing to do, but this is not easy in the laboratory.  The improvements must be made at every level, so the difficulty is significant.”

Among the challenges ahead are maintaining separation between the different memory systems, and minimizing loss of light as signals propagate through the optical fiber systems that would be used to transmit entangled photons.  

“Light is easily lost, and there’s not much that can be done about that from a fundamental physics standpoint,” said Kuzmich.  “The rates of these protocols go down rapidly as you try to scale up the systems.”

Kuzmich and his Georgia Tech research team have been developing quantum memory based on the interaction of light with neutral atoms such as rubidium.  They have made substantial progress over the past decade, but he says it’s not clear which approach will ultimately be used to create large-scale quantum communication system.

The most immediate applications for the quantum memory are in secure communications, in which the entanglement of photons with matter would provide a new form of encryption.

“The immediate focus is on communication, including memories and distributed systems, which is important for sharing and transmitting information,” Kuzmich explained.  “It also has implications for quantum computation because similar techniques are often used.”

In addition to Kuzmich, collaborators in the MURI include:

  • Luming Duan, professor of physics in the School of Physics at the University of Michigan, Ann Arbor, Michigan.
  • Dirk Englund, assistant professor of electrical engineering and applied physics in the School of Engineering and Applied Science at Columbia University, New York, New York.
  • Marko Lonkar, associate professor of electrical engineering in the School of Engineering and Applied Sciences at Harvard University, Cambridge, Massachusetts.
  • Brian Kennedy, professor of physics in the School of Physics at the Georgia Institute of Technology, Atlanta, Georgia.
  • Mikhail Lukin, professor of physics in the Department of Physics at Harvard University, Cambridge, Massachusetts.
  • Mark Saffman, professor of physics in the Department of Physics at the University of Wisconsin, Madison, Wisconsin.
  • Jelena Vuckovic, associate professor of electrical engineering in the Department of Electrical Engineering at Stanford University, Stanford, California.
  • Vladan Vuletic, the Lester Wolfe Professor of Physics in the School of Physics at Massachusetts Institute of Technology, Cambridge, Massachusetts.
  • Thad Walker, professor of physics in the Department of Physics at the University of Wisconsin, Madison, Wisconsin.

“If we are successful with this over the next five years, long-distance quantum communications may become promising for real-world implementation,” Kuzmich added.  “Integrating these advances with existing infrastructure – optical fiber that’s in the ground – will continue to be an important engineering challenge.”

This material is based upon work conducted under contract FA9550-12-1-0025.  Any opinions, findings and conclusions or recommendations expressed are those of the researchers and do not necessarily reflect the views of the Air Force Office of Scientific Research.

Research News & Publications Office
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 314
Atlanta, Georgia  30308  USA

Media Relations Contacts: John Toon (404-894-6986)(jtoon@gatech.edu) or Abby Robinson (404-385-3364)(abby@innovate.gatech.edu).

Writer: John Toon

Media Contact: 

John Toon

Research News & Publications Office

404-894-6986

jtoon@gatech.edu

Summary: 

The U.S. Air Force Office of Scientific Research (AFOSR) has awarded $8.5 million to a consortium of seven U.S. universities that will work together to determine the best approach for generating quantum memories based on interaction between light and matter.

Intro: 

The U.S. Air Force Office of Scientific Research (AFOSR) has awarded $8.5 million to a consortium of seven U.S. universities that will work together to determine the best approach for generating quantum memories based on interaction between light and matter.

Alumni: 

Town Hall Meeting with GT President Bud Peterson and Provost Rafael Bras

Thursday, January 26, 2012

In the coming weeks, President Bud Peterson and Provost Rafael Bras will jointly address the GT Academic Faculty during a series of one-hour, "town hall style" conversations.  These events will include brief presentations, followed by an open question-and-answer session with the audience.  Information about the first of these events is as follows...

 
What: Town Hall Meeting with GT President Bud Peterson and Provost Rafael Bras.
When: Monday, January 30 at 4 p.m.
Where: In the Student Center Theater.
Summary: 

Town Hall Meeting with GT President Bud Peterson and Provost Rafael Bras

Intro: 

Town Hall Meeting with GT President Bud Peterson and Provost Rafael Bras

Alumni: 

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