Tag Archives: speed

Physicists solve quantum tunneling mystery

An international team of scientists studying ultrafast physics have solved a mystery of quantum mechanics, and found that quantum tunneling is an instantaneous process.

The new theory could lead to faster and smaller electronic components, for which quantum tunneling is a significant factor. It will also lead to a better understanding of diverse areas such as electron microscopy, nuclear fusion and DNA mutations.

“Timescales this short have never been explored before. It’s an entirely new world,” said one of the international team, Professor Anatoli Kheifets, from The Australian National University (ANU).

“We have modelled the most delicate processes of nature very accurately.”

At very small scales quantum physics shows that particles such as electrons have wave-like properties – their exact position is not well defined. This means they can occasionally sneak through apparently impenetrable barriers, a phenomenon called quantum tunneling.

Quantum tunneling plays a role in a number of phenomena, such as nuclear fusion in the sun, scanning tunneling microscopy, and flash memory for computers. However, the leakage of particles also limits the miniaturisation of electronic components.

Professor Kheifets and Dr. Igor Ivanov, from the ANU Research School of Physics and Engineering, are members of a team which studied ultrafast experiments at the attosecond scale (10-18 seconds), a field that has developed in the last 15 years.

Until their work, a number of attosecond phenomena could not be adequately explained, such as the time delay when a photon ionised an atom.

“At that timescale the time an electron takes to quantum tunnel out of an atom was thought to be significant. But the mathematics says the time during tunneling is imaginary – a complex number – which we realised meant it must be an instantaneous process,” said Professor Kheifets.

“A very interesting paradox arises, because electron velocity during tunneling may become greater than the speed of light. However, this does not contradict the special theory of relativity, as the tunneling velocity is also imaginary” said Dr Ivanov, who recently took up a position at the Center for Relativistic Laser Science in Korea.

The team’s calculations, which were made using the Raijin supercomputer, revealed that the delay in photoionisation originates not from quantum tunneling but from the electric field of the nucleus attracting the escaping electron.

The results give an accurate calibration for future attosecond-scale research, said Professor Kheifets.

“It’s a good reference point for future experiments, such as studying proteins unfolding, or speeding up electrons in microchips,” he said.

The research is published in Nature Physics.

Source: ANU

World data transfer record back in Danish hands

Researchers at DTU Fotonik have reclaimed the world data transfer record.

By Lotte Krull


The world champions in data transmission are to be found in Lynbgy, where the High-Speed Optical Communications (HSOC) team at DTU Fotonik has just secured yet another world record. This time, the team has eclipsed the record that was set by researchers at the Karlsruhe Institut für Technologie, by proving that it is possible to transfer fully 43 terabits per second with just a single laser in the transmitter. This is an appreciable improvement on the German team’s previous record of 32 terabits per second.

The worldwide competition in data speed is contributing to developing the technology intended to accommodate the immense growth of data traffic on the internet, which is estimated to be growing by 40–50 per cent annually. What is more, emissions linked to the total energy consumption of the internet as a whole currently correspond to more than two per cent of the global man-made carbon emissions—which puts the internet on a par with the transport industry (aircraft, shipping etc.). However, these other industries are not growing by 40 per cent a year. It is therefore essential to identify solutions for the internet that make significant reductions in energy consumption while simultaneously expanding the bandwidth. This is precisely what the DTU team has demonstrated with its latest world record. DTU researchers have previously helped achieve the highest combined data transmission speed in the world—an incredible 1 petabit per second—although this involved using hundreds of lasers.

The researchers achieved their latest record by using a new type of optical fibre borrowed from the Japanese telecoms giant NNT. This type of fibre contains seven cores (glass threads) instead of the single core used in standard fibres, which makes it possible to transfer even more data. Despite the fact that it comprises seven cores, the new fibre does not take up any more space than the standard version.

The researchers’ record result has been verified and presented in what is known as a ‘post deadline paper’ at the CLEO 2014 international conference.

The High-Speed Optical Communications team at DTU Fotonik has held the world record in data transmission on numerous occasions. Back in 2009, these researchers were the first in the world to break the ‘terabit barrier’, which was considered an almost insurmountable challenge at that time, when they succeeded in transmitting more than 1 terabit per second—again using just a single laser. The benchmark has now been raised to 43 Tbit/s.

Source: DTU News