Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New system for detection of single atoms

Records photon bursts from optical cavity

Scientists have devised a new technique for real-time detection of freely moving individual neutral atoms that is more than 99.7% accurate and sensitive enough to discern the arrival of a single atom in less than one-millionth of a second, about 20 times faster than the best previous methods.

The system, described in Advance Online Publication at the Nature Physics web site by researchers at the Joint Quantum Institute (JQI) in College Park, MD, and the Universidad de Concepción in Chile, employs a novel means of altering the polarization of laser light trapped between two highly-reflective mirrors, in effect letting the scientists "see" atoms passing through by the individual photons that they scatter.

The ability to detect single atoms and molecules is essential to progress in many areas, including quantum information research, chemical detection and biochemical analysis.

"Existing protocols have been too slow to detect moving atoms, making it difficult to do something to them before they are gone. Our work relaxes that speed constraint," says coauthor David Norris of JQI. "Moreover, it is hard to distinguish between a genuine detection and a random 'false positive' without collecting data over a large period of time. Our system both filters the signal and reduces the detection time."

The scientists trap and cool a small population of atoms (rubidium is used in the current experiment) in a vacuum enclosure in such a way that they drop slowly, one at a time, through a hole 1.5 millimeters wide at the bottom of the trap. The atom then falls about 8 centimeters until it enters a tiny chamber, or cavity, that is fitted on opposite sides with highly reflective mirrors that face one another at a distance of about 2 millimeters. Passing through the center of both mirrors is a laser beam of wavelength 780 nanometers – just slightly longer than visible red light. The beam excites the atom as it falls between the mirrors, causing it to reradiate the light in all directions.

That arrangement is a familiar one for labs studying the interaction of atoms and photons. The JQI system, however, has two distinctively unique features.

First, the researchers use two polarizations of cavity light simultaneously: one (horizontal) which is pumped in to efficiently excite the atoms, and the other (vertical) which only appears when emitted by an atom inside the cavity. Although the descent of the atom through the chamber takes only 5 millionths of a second, that is 200 times longer than it takes for the atom to become excited and shed a photon, so this process can happen multiple times before the atom is gone.

Second, they create a magnetic field inside the cavity, which causes the laser light polarization to rotate slightly when an atom is present. Known as the Faraday effect, this phenomenon is typically very weak when observed with a single atom. However, since the light reflecting between the mirrors passes by the atom about 10,000 times, the result is a much larger rotation of a few degrees. This puts significantly more of the laser light into the vertical polarization, making the atoms easier to "see."

The light eventually escapes from the cavity and is fed through a polarizing beamsplitter which routes photons with horizontal polarization to one detector, and vertical polarization to another. Each arriving photon generates a unique time stamp whenever it triggers its detector.

Although the detector for the vertically polarized light should only be sensitive to light coming from an atom in the cavity, it can be fooled occasionally by stray light in the room. But because there are multiple emissions from each atom, there will be a burst of photons whenever an atom passes between the mirrors. This is the signature that the researchers use to confirm an atom detection.

"The chief difficulty lies in verifying that our detector is really sensitive enough to see single atoms, and not just large groups of them," says team leader Luis A. Orozco of JQI. "Fortunately, the statistics of the light serve as a fingerprint for single-atom emission, and we were able to utilize that information in our system."

The Joint Quantum Institute is a research partnership between the University of Maryland and the National Institute of Standards and Technology, with additional support and participation of the Laboratory for Physical Sciences. This research was conducted with support from the National Science Foundation and the National Institute of Standards and Technology.

* "Photon Burst Detection of Single Atoms in an Optical Cavity," M.L. Terraciano, R. Olson Knell, D.G. Norris, J. Jing, A. Fernandez and L.A. Orozco,, DOI 10.1038/NPHYS1282.

Luis Orozco | EurekAlert!
Further information:, DOI 10.1038/NPHYS1282

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>