20th October 2016
Quantum computers: 10-fold boost in stability achieved
A team at Australia's University of New South Wales has created a new quantum bit that remains in a stable superposition for 10 times longer than previously achieved.
Credit: Arne Laucht/UNSW
Australian engineers have created a new quantum bit which remains in a stable superposition for 10 times longer than previously achieved, dramatically expanding the time during which calculations could be performed in a silicon quantum computer.
The new quantum bit, consisting of the spin of a single atom in silicon and merged with an electromagnetic field – known as 'dressed qubit' – retains quantum information for much longer than 'undressed' atoms, opening up new avenues to build and operate the superpowerful quantum computers of the future.
"We have created a new quantum bit where the spin of a single electron is merged together with a strong electromagnetic field," comments Arne Laucht from the School of Electrical Engineering & Telecommunications at University of New South Wales (UNSW), lead author of the paper. "This quantum bit is more versatile and more long-lived than the electron alone, and will allow us to build more reliable quantum computers."
Building a quantum computer is a difficult and ambitious challenge, but has potential to deliver revolutionary tools for otherwise impossible calculations – such as the design of complex drugs and advanced materials, or the rapid search of massive, unsorted databases. Its speed and power lie in the fact that quantum systems can host multiple 'superpositions' of different initial states, which in a computer are treated as inputs which, in turn, all get processed at the same time.
"The greatest hurdle in using quantum objects for computing is to preserve their delicate superpositions long enough to allow us to perform useful calculations," said Andrea Morello, Program Manager in the Centre for Quantum Computation & Communication Technology at UNSW. "Our decade-long research program had already established the most long-lived quantum bit in the solid state, by encoding quantum information in the spin of a single phosphorus atom inside a silicon chip placed in a static magnetic field," he said.
What Laucht and colleagues did was push this further: "We have now implemented a new way to encode the information: we have subjected the atom to a very strong, continuously oscillating electromagnetic field at microwave frequencies, and thus we have 'redefined' the quantum bit as the orientation of the spin with respect to the microwave field."
Tuning gates (red), microwave antenna (blue), and single electron transistor used for spin readout (yellow).
Credit: Guilherme Tosi & Arne Laucht/UNSW
The results are striking: since the electromagnetic field steadily oscillates at a very high frequency, any noise or disturbance at a different frequency results in a zero net effect. The UNSW researchers achieved an improvement by a factor of 10 in the time span during which a quantum superposition can be preserved, with a dephasing time of T2*=2.4 milliseconds.
"This new 'dressed qubit' can be controlled in a variety of ways that would be impractical with an 'undressed qubit'," adds Morello. "For example, it can be controlled by simply modulating the frequency of the microwave field, just like an FM radio. The 'undressed qubit' instead requires turning the amplitude of the control fields on and off, like an AM radio. In some sense, this is why the dressed qubit is more immune to noise: the quantum information is controlled by the frequency, which is rock-solid, whereas the amplitude can be more easily affected by external noise."
Since the device is built upon standard silicon technology, this result paves the way to the construction of powerful and reliable quantum processors based on the same fabrication process already used for today's computers. The UNSW team leads the world in developing silicon quantum computing and Morello's team is part of a consortium who have struck a A$70 million deal between UNSW, researchers, business, and the Australian government to develop a prototype silicon quantum integrated circuit – a major step in building the world's first quantum computer in silicon.
A functional quantum computer would allow massive increases in speed and efficiency for certain computing tasks – even when compared with today's fastest silicon-based 'classical' computers. In a number of key areas – such as searching enormous databases, solving complicated sets of equations, and modelling atomic systems such as biological molecules or drugs – they would far surpass today's computers. They would also be extremely useful in the finance and healthcare industries, and for government, security and defence organisations.
Quantum computers could identify and develop new medicines by vastly accelerating the computer-aided design of pharmaceutical compounds (minimising lengthy trial and error testing), and develop new, lighter and stronger materials spanning consumer electronics to aircraft. They would also make possible new types of computing applications and solutions that are beyond our ability to foresee.
The UNSW study appears this week in the peer-reviewed journal, Nature Nanotechnology.
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12th October 2016
Scientists create the smallest ever transistor – just a single nanometre long
Researchers at the Department of Energy's Lawrence Berkeley National Laboratory have demonstrated a working 1 nanometre (nm) transistor.
Credit: Sujay Desai/UC Berkeley
For more than a decade, engineers have been eyeing the finish line in the race to shrink the size of components in integrated circuits. They knew that the laws of physics had set a 5-nanometre threshold on the size of transistor gates among conventional semiconductors, about one-third the size of high-end 14-nanometre-gate transistors currently on the market.
However, some laws are made to be broken, or at least challenged.
A research team led by faculty scientist Ali Javey at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has done just that by creating a transistor with a functioning 1-nanometre gate. For comparison, a strand of human hair is about 50,000 nanometres thick.
"We made the smallest transistor reported to date," said Javey, lead principal investigator of the Electronic Materials program in Berkeley Lab's Materials Science Division. "The gate length is considered a defining dimension of the transistor. We demonstrated a 1-nanometre-gate transistor, showing that with the choice of proper materials, there is a lot more room to shrink our electronics."
The key was to use carbon nanotubes and molybdenum disulfide (MoS2), an engine lubricant commonly sold in auto parts shops. MoS2 is part of a family of materials with immense potential for applications in LEDs, lasers, nanoscale transistors, solar cells, and more.
This breakthrough could help in keeping alive Intel co-founder Gordon Moore's prediction that the density of transistors on integrated circuits would double every two years, enabling the increased performance of our laptops, mobile phones, televisions, and other electronics.
"The semiconductor industry has long assumed that any gate below 5 nanometres wouldn't work – so anything below that was not even considered," said study lead author Sujay Desai, a graduate student in Javey's lab. "This research shows that sub-5-nanometre gates should not be discounted. Industry has been squeezing every last bit of capability out of silicon. By changing the material from silicon to MoS2, we can make a transistor with a gate that is just 1 nanometre in length, and operate it like a switch."
"This work demonstrated the shortest transistor ever," said Javey, who is also a UC Berkeley professor of electrical engineering and computer sciences. "However, it's a proof of concept. We have not yet packed these transistors onto a chip, and we haven't done this billions of times over. We also have not developed self-aligned fabrication schemes for reducing parasitic resistances in the device. But this work is important to show that we are no longer limited to a 5-nanometre gate for our transistors. Moore's Law can continue a while longer by proper engineering of the semiconductor material and device architecture."
His team's research is published this month in the peer-reviewed journal Science.
Credit: Qingxiao Wang/UT Dallas
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3rd September 2016
DNA is sequenced in outer space for the first time
DNA has been sequenced in space for the first time, with astronaut Kate Rubins using a MinION device aboard the International Space Station.
High above the Earth, at an altitude of 330 km (205 mi), NASA has conducted the first ever space-based genome sequencing. This was made possible by a handheld device called a MinION, used aboard the International Space Station (ISS) by astronaut Kate Rubins.
Genetics have come a long way since 1953, when James Watson and Francis Crick published their famous discovery, which identified the double helical structure of DNA, the molecular instructions used in the development and functioning of all known living organisms. By the 1970s, gene expression could be controlled and manipulated through genetic engineering, which led to the first genetically modified animals and plants. During the final decades of the 20th century, teams of biologists attempted large-scale genetics projects, sequencing entire genomes, which culminated in the Human Genome Project. The latter was a $2.7 billion endeavour that involved hundreds of scientists from laboratories around the world.
Today, in the 21st century, the costs of sequencing DNA and the time required to do so have fallen at unprecedented rates – thanks to exponential advances in technology progressing faster than Moore's Law. Hundreds of thousands of human genomes have now been sequenced, with a billion likely to be read by 2025, alongside those of many more animals, plants and other lifeforms. Given the increasing portability of the hardware and its relative ease of use, it was only a matter of time before this technology found its way into space. This follows a similar milestone in November 2014 when the first 3D printer was used on the ISS.
The MinION device used by Rubins is small and light enough to carry in your palm and is easily attached to a laptop with a USB port. It was tested by researchers last year who sequenced the full genome of the bacteria Escherichia Coli. Developed by UK-based company Oxford Nanopore Technologies, the MinION works by a system of tiny protein "nanopores" dotted across an electrically-resistant membrane. A current is applied and flows through the aperture of the nanopore only. Individual molecules are identified based on a distinctive signature they reveal as they pass by and disrupt the current. Intact strands of DNA can be processed in real time and catalogued according to each of the four nucleobases – guanine (G), adenine (A), thymine (T), and cytosine (C) – as explained in this video.
Credit: Oxford Nanopore Technologies Limited
Dr. Rubins, who has been aboard the ISS since 6th July, sequenced the DNA of bacteria, viruses and rodents. A team back on the ground then analysed the data and compared it to identical samples processed in their laboratory. The microgravity environment and other conditions on the space station appeared to have little or no effect in terms of harming the results.
"Until recently, technology for sequencing in space hasn't been available because sequencers are generally large bulky instruments," said Charles Chiu, director of the Abbott Viral Diagnostics and Discovery Centre at the University of California, who led the study. "It didn't turn out to be a huge problem. We essentially got equivalent data, and it's of very high quality, probably within the top 20% of nanopore runs that we do routinely here on Earth."
In future missions, the sequencing of DNA could enable crew members to rapidly diagnose an illness, or identify microbes growing aboard the station and what health threat is present. This would be particularly important to help protect astronauts on long-duration missions to Mars, for example.
"Onboard sequencing makes it possible for the crew to know what is in their environment at any time," said Sarah Castro-Wallace, NASA microbiologist and ISS project manager. "That allows us on the ground to take appropriate action – do we need to clean this up right away, or will taking antibiotics help or not? We can resupply the station with disinfectants and antibiotics now; but once crews move beyond the station's low Earth orbit, we need to know when to save those precious resources and when to use them."
In addition, the MinION and other sequencers can become a tool for more advanced science investigations in space. Researchers could use them to examine changes in genetic material or gene expression while in orbit, for example, rather than waiting for samples to be returned to Earth for testing. The ability to read genomes in space may also help in the detection of DNA-based life elsewhere in the universe. Maybe in the far future, similar devices will be routinely used on Earth-like planetary surfaces to catalogue alien species.
"Welcome to systems biology in space," said Rubins after sequencing the DNA samples, thanking the ground team for their efforts. "It is very exciting to be with you guys together at the dawn of genomics biology and systems biology in space."
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19th July 2016
Smallest ever hard disk writes information atom by atom
Scientists in the Netherlands, working at the limits of miniaturisation, have used one bit per atom to create 1 kilobyte of data storage.
Every day, modern society creates more than a billion gigabytes of new data. To store all this information, it is increasingly important that each single bit occupies as little space as possible. A team of scientists at the Kavli Institute of Nanoscience at Delft University, Netherlands, managed to bring this reduction to the ultimate limit: they built a memory of 1 kilobyte (8,000 bits), where each bit is represented by the position of one single chlorine atom.
"In theory, this storage density would allow all books ever created by humans to be written on a single post stamp", says lead scientist Sander Otte. They reached a storage density of 500 Terabits per square inch (Tbpsi), 500 times better than the best commercial hard disk currently available. His team reports on this breakthrough in Nature Nanotechnology.
In 1959, physicist Richard Feynman challenged his colleagues to engineer the world at the smallest possible scale. In his famous lecture, There's Plenty of Room at the Bottom, he speculated that a platform allowing us to arrange individual atoms, in an exact orderly pattern, would make it possible to store one piece of information per atom. To honour the visionary Feynman, Otte and his team have now coded a section of Feynman's lecture on an area 100 nanometres wide.
STM scan (96 nm wide, 126 nm tall) of the 1 kB memory, written to a section of Feynman's lecture, There's Plenty of Room at the Bottom.
The team used a scanning tunnelling microscope (STM), in which a sharp needle probes the atoms of a surface, one by one. Using these probes, scientists not only see the atoms, but can also push them around: "You could compare it to a sliding puzzle", Otte explains. "Every bit consists of two positions on a surface of copper atoms, and one chlorine atom that we can slide back and forth between these two positions. If the chlorine atom is in the top position, there is a hole beneath it – we call this a 1. If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a 0." Because the chlorine atoms are surrounded by other chlorine atoms, except near the holes, they keep each other in place. That is why this method with holes is much more stable than methods with loose atoms and more suitable for data storage.
The researchers from Delft organised their memory in blocks of 8 bytes (64 bits). Each block has a marker, made of the same type of 'holes' as the raster of chlorine atoms. Inspired by the pixelated square barcodes (QR codes) often used to scan tickets for airplanes and concerts, these markers work like miniature QR codes that carry information about the precise location of the block on the copper layer. The code will also indicate if a block has been damaged, for instance due to some local contaminant or an error in the surface. This allows memory to be scaled up easily to very big sizes, even if the copper surface is not entirely perfect.
The new method offers excellent prospects in terms of stability and scalability. Still, this type of memory should not be expected in commercial use anytime soon: "In its current form, the memory can operate only in very clean vacuum conditions and at liquid nitrogen temperature (77 K), so the actual storage of data on an atomic scale is still some way off," explains Otte. "But through this achievement, we have certainly come a big step closer".
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