A new quantum state of matter?

Researchers at the University of Pittsburgh have made advances in better understanding correlated quantum matter by studying topological states in order to advance quantum computing, a method that harnesses the power of atoms and molecules for computational tasks.

Through his research, W. Vincent Liu and his team have been studying orbital degrees of freedom and nano-Kelvin cold atoms in optical lattices (a set of standing wave lasers) to better understand new quantum states of matter. From that research, a surprising topological semimetal has emerged.



Since the discovery of the quantum Hall effect by Klaus Van Klitzing in 1985, researchers like Liu have been particularly interested in studying topological states of matter, that is, properties of space unchanged under continuous deformations or distortions such as bending and stretching. The quantum Hall effect proved that when a magnetic field is applied perpendicular to the direction a current is flowing through a metal, a voltage is developed in the third perpendicular direction. Liu's work has yielded similar yet remarkably different results.

"We never expected a result like this based on previous studies," said Liu. "We were surprised to find that such a simple system could reveal itself as a new type of topological state -- an insulator that shares the same properties as a quantum Hall state in solid materials."
"This new quantum state is very reminiscent of quantum Hall edge states," said Liu. "It shares the same surface appearance, but the mechanism is entirely different: This Hall-like state is driven by interaction, not by an applied magnetic field."

Liu says this liquid matter could potentially lead toward topological quantum computers and new quantum devices for topological quantum telecommunication. Next, he and his team plan to measure quantities for a cold-atom system to check these predicted quantum-like properties.

Quantum cryptography breached?

Quantum cryptography has been pushed onto the market as a way to provide absolute security for communications and, as far as we know, no current quantum cryptographic system has been compromised in the field. It is already used in Swiss elections to ensure that electronic vote data is securely transmitted to central locations.

Quantum cryptography relies on the concept of entanglement. With entanglement, some statistical correlations are measured to be larger than those found in experiments based purely on classical physics. Cryptographic security works by using the correlations between entangled photons pairs to generate a common secret key. If an eavesdropper intercepts the quantum part of the signal, the statistics change, revealing the presence of an interloper.

The Swiss general approach can be summed up as follows: if you can fool a detector into thinking a classical light pulse is actually a quantum light pulse, then you might just be able to defeat a quantum cryptographic system. But even then the attack should fail, because quantum entangled states have statistics that cannot be achieved with classical light sources—by comparing statistics, you could unmask the deception.

But there's a catch here. I can make a classical signal that is perfectly correlated to any signal at all, provided I have time to measure said signal and replicate it appropriately. In other words, these statistical arguments only apply when there is no causal connection between the two measurements.

You might think that this makes intercepting the quantum goodness of a cryptographic system easy. But you would be wrong. When Eve intercepts the photons from the transmitting station run by Alice, she also destroys the photons. And even though she gets a result from her measurement, she cannot know the photons' full state. Thus, she cannot recreate, at the single photon level, a state that will ensure that Bob, at the receiving station, will observe identical measurements.

That is the theory anyway. But this is where the second loophole comes into play. We often assume that the detectors are actually detecting what we think they are detecting. In practice, there is no such thing as a single photon, single polarization detector. Instead, what we use is a filter that only allows a particular polarization of light to pass and an intensity detector to look for light. The filter doesn't care how many photons pass through, while the detector plays lots of games to try and be single photon sensitive when, ultimately, it is not. It's this gap between theory and practice that allows a carefully manipulated classical light beam to fool a detector into reporting single photon clicks.

Since Eve has measured the polarization state of the photon, she knows what polarization state to set on her classical light pulse in order to fake Bob into recording the same measurement result. When Bob and Alice compare notes, they get the right answers and assume everything is on the up and up.
The researchers demonstrated that this attack succeeds with standard (but not commercial) quantum cryptography equipment under a range of different circumstances. In fact, they could make the setup outperform the quantum implementation for some particular settings.

(Adapted from ArsTechnica)

Quantum Cloning Advances

Quantum cloning is the process that takes an arbitrary, unknown quantum state and makes an exact copy without altering the original state in any way. Quantum cloning is forbidden by the laws of quantum mechanics as shown by the no cloning theorem. Though perfect quantum cloning is not possible, it is possible to perform imperfect cloning, where the copies have a non-unit fidelity with the state being cloned.

The quantum cloning operation is the best way to make copies of quantum information therefore cloning is an important task in quantum information processing, especially in the context of quantum cryptography. Researchers are seeking ways to build quantum cloning machines, which work at the so called quantum limit. Quantum cloning is difficult because quantum mechanics laws only allow for an approximate copy—not an exact copy—of an original quantum state to be made, as measuring such a state prior to its cloning would alter it. The first cloning machine relied on stimulated emission to copy quantum information encoded into single photons.

Scientists in China have now produced a theory for a quantum cloning machine able to produce several copies of the state of a particle at atomic or sub-atomic scale, or quantum state. A team from Henan Universities in China, in collaboration with another team at the Institute of Physics of the Chinese Academy of Sciences, have produced a theory for a quantum cloning machine able to produce several copies of the state of a particle at atomic or sub-atomic scale, or quantum state. The advance could have implications for quantum information processing methods used, for example, in message encryption systems.

In this study, researchers have demonstrated that it is theoretically possible to create four approximate copies of an initial quantum state, in a process called asymmetric cloning. The authors have extended previous work that was limited to quantum cloning providing only two or three copies of the original state. One key challenge was that the quality of the approximate copy decreases as the number of copies increases.

The authors were able to optimize the quality of the cloned copies, thus yielding four good approximations of the initial quantum state. They have also demonstrated that their quantum cloning machine has the advantage of being universal and therefore is able to work with any quantum state, ranging from a photon to an atom. Asymmetric quantum cloning has applications in analyzing the security of messages encryption systems, based on shared secret quantum keys.

The Future of Computers - Quantum nanocomputers

A quantum computer uses quantum mechanical phenomena, such as entanglement and superposition to process data. Quantum computation aims to use the quantum properties of particles to represent and structure data using quantum mechanics to understand how to perform operations with this data.

The quantum mechanical properties of atoms or nuclei allow these particles to work together as quantum bits, or qubits. These qubits work together to form the computer’s processor and memory and can can interact with each other while being isolated from the external environment and this enables them to perform certain calculations much faster than conventional computers. By computing many different numbers simultaneously and then interfering the results to get a single answer, a quantum computer can perform a large number of operations in parallel and ends up being much more powerful than a digital computer of the same size.

A quantum nanocomputer would work by storing data in the form of atomic quantum states or spin. Technology of this kind is already under development in the form of single-electron memory (SEM) and quantum dots. By means of quantum mechanics, waves would store the state of each nanoscale component and information would be stored as the spin orientation or state of an atom. With the correct setup, constructive interference would emphasize the wave patterns that held the right answer, while destructive interference would prevent any wrong answers.

The energy state of an electron within an atom, represented by the electron energy level or shell, can theoretically represent one, two, four, eight, or even 16 bits of data. The main problem with this technology is instability. Instantaneous electron energy states are difficult to predict and even more difficult to control. An electron can easily fall to a lower energy state, emitting a photon; conversely, a photon striking an atom can cause one of its electrons to jump to a higher energy state.

I promise to write a series of articles on quantum issues very shortly...

The Future of Computers - Electronic nanocomputers

Due to our fifty years of experience with electronic computing devices, including the extensive research and industrial infrastructure built up since the late 1940s, advances in nanocomputing technology are likely to come in this direction making the electronic nanocomputers appear to present the easiest and most likely direction in which to continue nanocomputer development in the near future.

Electronic nanocomputers would operate in a manner similar to the way present-day microcomputers work. The main difference is one of physical scale. More and more transistor s are squeezed into silicon chips with each passing year; witness the evolution of integrated circuits (IC s) capable of ever-increasing storage capacity and processing power.

The ultimate limit to the number of transistors per unit volume is imposed by the atomic structure of matter. Most engineers agree that technology has not yet come close to pushing this limit. In the electronic sense, the term nanocomputer is relative; by 1970s standards, today's ordinary microprocessors might be called nanodevices.

How it works

The power and speed of computers have grown rapidly because of rapid progress in solid-state electronics dating back to the invention of the transistor in 1948. Most important, there has been exponential increase in the density of transistors on integrated-circuit computer chips over the past 40 years. In that time span, though, there has been no fundamental change in the operating principles of the transistor.

Even microelectronic transistors no more than a few microns (millionths of a meter) in size are bulk-effect devices. They still operate using small electric fields imposed by tiny charged metal plates to control the mass action of many millions of electrons.

Although electronic nanocomputers will not use the traditional concept of transistors for its components, they will still operate by storing components, information in the positions of electrons.

At the current rate of miniaturization, the conventional transistor technology will reach a minimum size limit in a few years. At that point, smallscale quantum mechanical efects, such as the tunneling of electrons through barriers made from matter or electric fields, will begin to dominate the essential effects that permit a mass-action semiconductor device to operate Still, an electronic nanocomputer will continue to represent information in the storage and movement of electrons.

Nowadays, most eletronic nanocomputers are created through microscopic circuits using nanolithography.

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The Future of Computers - Nanocomputers

Scientific discussion of the development and fabrication of nanometer-scale devices began in 1959 with an influential lecture by the late, renowned physicist Richard Feynman. Feynman observed that it is possible, in principle, to build and operate submicroscopic machinery. He proposed that large numbers of completely identical devices might be assembled by manipulating atoms one at a time.

Feynman's proposal sparked an initial flurry of interest but it did not broadly capture the imagination of the technical community or the public. At the time, building structures one atom at a time seemed out of reach. Throughout the 1960s and 1970s advances in diverse fields prepared the scientific community for the first crude manipulations of nanometer-scale structures. The most obvious development was the continual miniaturization of digital electronic circuits, based primarily upon the invention of the transistor by Shockley, Brattain, and Bardeen in 1948 and the invention of the integrated circuit by Noyce, Kilby, and others in the late 1950s. In 1959, it was only possible to put one transistor on an integrated circuit. Twenty years later, circuits with a few thousand transistors were commonplace.

Scientists are trying to use nanotechnology to make very tiny chips, electrical conductors and logic gates. Using nanotechnology, chips can be built up one atom at a time and hence there would be no wastage of space, enabling much smaller devices to be built. Using this technology, logic gates will be composed of just a few atoms and electrical conductors (called nanowires) will be merely an atom thick and a data bit will be represented by the presence or absence of an electron.

A nanocomputer is a computer whose physical dimensions are microscopic; smaller than the microcomputer, which is smaller than the minicomputer. (The minicomputer is called "mini" because it was a lot smaller than the original (mainframe) computers.)

A component of nanotechnology, nanocomputing will, as suggested or proposed by researchers and futurists, give rise to four types of nanocomputers:

• Electronic nanocomputers

• Chemical and Biochemical nanocomputers

• Mechanical nanocomputers

• Quantum nanocomputers

Keep reading the next posts…

The Future of Computers - Overview

Computers' Evolution

The history of computers and computer technology thus far has been a long and a fascinating one, stretching back more than half a century to the first primitive computing machines. These machines were huge and complicated affairs, consisting of row upon row of vacuum tubes and wires, often encompassing several rooms to fit it all in.

In the past twenty years, there has been a dramatic increase in the processing speed of computers, network capacity and the speed of the internet. These advances have paved the way for the revolution of fields such as quantum physics, artificial intelligence and nanotechnology. These advances will have a profound effect on the way we live and work, the virtual reality we see in movies like the Matrix, may actually come true in the next decade or so.

Today's computers operate using transistors, wires and electricity. Future computers might use atoms, fibers and light. Take a moment to consider what the world might be like, if computers the size of molecules become a reality. These are the types of computers that could be everywhere, but never seen. Nano sized bio-computers that could target specific areas inside your body. Giant networks of computers, in your clothing, your house, your car. Entrenched in almost every aspect of our lives and yet you may never give them a single thought.

As anyone who has looked at the world of computers lately can attest, the size of computers has been reduced sharply, even as the power of these machines has increased at an exponential rate. In fact, the cost of computers has come down so much that many households now own not only one, but two, three or even more, PCs.

As the world of computers and computer technology continues to evolve and change, many people, from science fiction writers and futurists to computer workers and ordinary users have wondered what the future holds for the computer and related technologies. Many things have been pictured, from robots in the form of household servants to computers so small they can fit in a pocket. Indeed, some of these predicted inventions have already come to pass, with the introduction of PDAs and robotic vacuum cleaners.

Understanding the theories behind these future computer technologies is not for the meek. My research into quantum computers was made all the more difficult after I learned that in light of her constant interference, it is theoretically possible my mother-in-law could be in two places at once.

Nanotechnology is another important part of the future of computers, expected to have a profound impact on people around the globe. Nanotechnology is the process whereby matter is manipulated at the atomic level, providing the ability to “build” objects from their most basic parts. Like robotics and artificial intelligence, nanotechnology is already in use in many places, providing everything from stain resistant clothing to better suntan lotion. These advances in nanotechnology are likely to continue in the future, making this one of the most powerful aspects of future computing.

In the future, the number of tiny but powerful computers you encounter every day will number in the thousands, perhaps millions. You won't see them, but they will be all around you. Your personal interface to this powerful network of computers could come from a single computing device that is worn on or in the body.

Quantum computers are also likely to transform the computing experience, for both business and home users. These powerful machines are already on the drawing board, and they are likely to be introduced in the near future. The quantum computer is expected to be a giant leap forward in computing technology, with exciting implications for everything from scientific research to stock market predictions.

Moore's law

Visit any site on the web writing about the future of computers and you will most likely find mention of Moore's Law. Moore's Law is not a strictly adhered to mathematical formula, but a prediction made by Intel's founder co-founder Gordon Moore in 1965 in a paper where he noted that number of components in integrated circuits had doubled every year from the invention of the integrated circuit in 1958 until 1965 and predicted that the trend would continue "for at least ten years".

Moore predicted that computing technology would increase in value at the same time it would decrease in cost describing a long-term trend in the history of computing hardware. More specifically, that innovation in technology would allow for the number of transistors that can be placed inexpensively on an integrated circuit to double approximately every two years. The trend has continued for more than half a century and is not expected to stop until 2015 or later.

A computer transistor acts like a small electronic switch. Just like the light switch on your wall, a transistor has only two states, On or Off. A computer interprets this on/off state as a 1 or a 0. Put a whole bunch of these transistors together and you have a computer chip. The central processing unit (CPU) inside your computer probably has around 500 million transistors.

Shrinking transistor size not only makes chips smaller, but faster. One benefit of packing transistors closer together is that the electronic pulses take less time to travel between transistors. This can increase the overall speed of the chip. The capabilities of many digital electronic devices are strongly linked to Moore's law: processing speed, memory capacity, sensors and even the number and size of pixels in digital cameras. All of these are improving at (roughly) exponential rates as well.

Not everyone agrees that Moore's Law has been accurate throughout the years, (the prediction has changed since its original version), or that it will hold true in the future. But does it really matter? The pace at which computers are doubling their smarts is happening fast enough for me.

Thanks to the innovation and drive of Gordon Moore and others like him, computers will continue to get smaller, faster and more affordable.