Electricity from tiny pieces
A research team from NPL and the University of Cambridge has developed an electron pump that picks electrons up one at a time and moves them across a barrier to create a very well‑defined electrical current. The team used a nano‑scale semiconductor device called a ‘quantum dot’, which is 0.0001 mm wide, to pump electrons one at a time through a circuit at a rate of almost one billion per second. The 150 picoampere current produced is 300 times larger than previously achieved at a confirmed pumping accuracy of one part per million, thereby taking an important step towards the redefinition of the ampere, the SI unit for electrical current. This quantum current standard will make the ampere easier to realise in practice and the precise control of electrons in semiconductor devices demonstrated by this research will help develop smaller high-precision electronic devices.
MASER power comes out of the cold
For half a century the MASER has been the forgotten, inconvenient cousin of the LASER. Our design breakthrough will enable MASERs to be used by industry and consumers.”
Mark Oxborrow, co-author of the study at NPL
Scientists from NPL and Imperial College London have demonstrated the world’s first solid‑state ‘MASER’ capable of operating at room temperature in air with no applied magnetic field. The breakthrough, published in the journal Nature, means that the cost to manufacture and operate MASERs could be dramatically reduced, paving the way for their wider adoption.
MASER is an acronym for Microwave Amplification by Stimulated Emission of Radiation. Instead of creating intense beams of light, as LASERs do, MASERs deliver a concentrated beam of microwaves. However, conventional MASER technology has had little impact compared with the LASER because getting it to work has always required extreme conditions such as low pressures and temperatures that are difficult, and expensive, to produce.
A room‑temperature MASER opens up new possibilities; it could potentially be used to make more sensitive medical instruments for scanning patients, improved chemical sensors for remotely detecting explosives, lower‑noise read‑out mechanisms for quantum computers and better radio telescopes for potentially detecting life on other planets.
This research was chosen as one of the top 10 breakthroughs for 2012 by Physics World, the membership magazine of the Institute of Physics.
Trapping ions on a chip
We managed to produce an essential device or tool, which is critical for state-of-the-art research and development in quantum technologies.”
Alastair Sinclair, co-author of the 'trapping ions on a chip' study at NPL
A ground‑breaking device, demonstrated for the first time at NPL, could help usher in the long-awaited era of quantum computing. Quantum algorithms can perform certain calculations exponentially faster than classical systems and quantum cryptography could theoretically improve data security to an almost unbeatable level. This information technology is based on the use of entangled particles known as quantum bits, or ‘qubits’, to perform calculations. NPL’s novel device is a 3D ion microtrap array made from a silica‑on‑silicon wafer using a scalable microfabrication process. During the research, NPL scientists were able to confine individual ions, as well as strings of up to 14 ions, in a single segment of the microtrap array. The microfabrication process will enable the creation of more complex devices which could handle even larger numbers of ions, while retaining the ability to control particles at the individual level.
A new generation of acoustic measurements
NPL scientists have made the first measurements of airborne acoustic free‑field pressures using a laser technique based on photon correlation spectroscopy. Two laser beams are set up so that they intersect and produce an interference fringe pattern. When sound is produced by a source (such as a loudspeaker), the intensity of light scattered by particles in the air as they pass through the fringe pattern changes. This intensity change can be detected, and the acoustic free‑field pressure directly calculated. The use of optical techniques like these can not only potentially provide new calibration capabilities applicable to existing commercially available microphones, but also help accelerate the development of new microphone technologies and other acoustic devices.
Scientific first in air quality data
Polycyclic aromatic hydrocarbons (PAHs) are organic compounds, some of which are toxic and carcinogenic. They are produced from the incomplete burning of carbon‑containing fuels and their measurement is important for public health and environmental protection. NPL scientists have conducted the first ever experimental assessment of the effect of atmospheric degradation on the annual average concentration of a PAH called benzo[a]pyrene, in air. This scientific first adds value to data obtained by the UK PAH Monitoring and Analysis Network, which NPL operates on behalf of the Department for Environment, Food and Rural Affairs (Defra), and will help position the UK to meet future requirements of EU air quality directives and improve respiratory health.
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For more stories from 2012, please download our Annual Review (1.17 MB - PDF)