David Kirkpatrick

July 22, 2010

The first beneficiaries of quantum computing?

Filed under: Science — Tags: , , , , — David Kirkpatrick @ 5:12 pm

Chemists. Who’d a thunk that one. It’s not totally there yet, but quantum chemistry may transform the field.

From the link:

There’s no shortage of scientists waiting to get their hands on quantum computers. Cryptographers, in particular, are licking their lips in anticipation.

But there’s another group who are already beginning to benefit from the first few iterations of quantum computing devices: chemists.

Various scientists have pointed out that it is possible to study the properties of a particular quantum system using another controllable quantum system.

This kind of quantum simulation has huge implications for chemistry. No longer would it be necessary to mess around with real atoms, ions and molecules in messy experiments with test tubes and bunsen burners.

Instead it ought to be possible to perfectly simulate what goes on using a quantum computer set up in the right way. That’s the theory anyway. The practice is inevitably more tricky.

February 15, 2010

A little nano bling …

… may lead to some serious nanotech applications in medicine, data protection and supercomputing.

The release:

Digging deep into diamonds, applied physicists advance quantum science and technology

Diamond nanowire device could lead to new class of diamond nanomaterials suitable for quantum cryptography, quantum computing, and magnetic field imaging

IMAGE: A diamond-based nanowire device. Researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just “one-of-a-kind ” designs,…

Click here for more information.

CAMBRIDGE, Mass., By creating diamond-based nanowire devices, a team at Harvard has taken another step towards making applications based on quantum science and technology possible.

The new device offers a bright, stable source of single photons at room temperature, an essential element in making fast and secure computing with light practical.

The finding could lead to a new class of nanostructured diamond devices suitable for quantum communication and computing, as well as advance areas ranging from biological and chemical sensing to scientific imaging.

Published in the February 14th issue of Nature Nanotechnology, researchers led by Marko Loncar, Assistant Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), found that the performance of a single photon source based on a light emitting defect (color center) in diamond could be improved by nanostructuring the diamond and embedding the defect within a diamond nanowire.

Scientists, in fact, first began exploiting the properties of natural diamonds after learning how to manipulate the electron spin, or intrinsic angular momentum, associated with the nitrogen vacancy (NV) color center of the gem. The quantum (qubit) state can be initialized and measured using light.

The color center “communicates” by emitting and absorbing photons. The flow of photons emitted from the color center provides a means to carry the resulting information, making the control, capture, and storage of photons essential for any kind of practical communication or computation. Gathering photons efficiently, however, is difficult since color-centers are embedded deep inside the diamond.

“This presents a major problem if you want to interface a color center and integrate it into real-world applications,” explains Loncar. “What was missing was an interface that connects the nano-world of a color center with macro-world of optical fibers and lenses.”

The diamond nanowire device offers a solution, providing a natural and efficient interface to probe an individual color center, making it brighter and increasing its sensitivity. The resulting enhanced optical properties increases photon collection by nearly a factor of ten relative to natural diamond devices.

“Our nanowire device can channel the photons that are emitted and direct them in a convenient way,” says lead-author Tom Babinec, a graduate student at SEAS.

Further, the diamond nanowire is designed to overcome hurdles that have challenged other state-of-the-art systems—such as those based on fluorescent dye molecules, quantum dots, and carbon nanotubes—as the device can be readily replicated and integrated with a variety of nano-machined structures.

The researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just “one-of-a-kind” designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely.

“We consider this an important step and enabling technology towards more practical optical systems based on this exciting material platform,” says Loncar. “Starting with these synthetic, nanostructured diamond samples, we can start dreaming about the diamond-based devices and systems that could one day lead to applications in quantum science and technology as well as in sensing and imaging.”


Loncar and Babinec’s co-authors included research scholar Birgit Hausmann, graduate student Yinan Zhang, and postdoctoral student Mughees Khan, all at SEAS; graduate student Jero Maze in the Department of Physics at Harvard; and faculty member Phil R. Hemmer at Texas A&M University.

The researchers acknowledge the following support: Nanoscale Interdisciplinary Research Team (NIRT) grant from National Science Foundation (NSF), the NSF-funded Nanoscale Science and Engineering Center at Harvard (NSEC); the Defense Advanced Research Projects Agency (DARPA); and a National Defense Science and Engineering Graduate Fellowship and National Science Foundation Graduate Fellowship. All devices have been fabricated at the Center for Nanoscale Systems (CNS) at Harvard.

April 30, 2009

Quantum cryptography becoming practical

Looks like things are moving that direction. Very cool.

The release:

Computer hackers R.I.P. — making quantum cryptography practical

Quantum cryptography, a completely secure means of communication, is much closer to being used practically as researchers from  and Cambridge University’s Cavendish Laboratory have now developed high speed detectors capable of receiving information with much higher key rates, thereby able to receive more information faster.

Published as part of IOP Publishing’s New Journal of Physics‘ Focus Issue on ‘Quantum Cryptography: Theory and Practice’, the journal paper, ‘Practical gigahertz quantum key distribution based on avalanche photodiodes’, details how quantum communication can be made possible without having to use cryogenic cooling and/or complicated optical setups, making it much more likely to become commercially viable soon.

One of the first practical applications to emerge from advances in the often baffling study of quantum mechanics, quantum cryptography has become the soon-to-be-reached gold standard in secure communications.

Quantum mechanics describes the fundamental nature of matter at the atomic level and offers very intriguing, often counter-intuitive, explanations to help us understand the building blocks that construct the world around us. Quantum cryptography uses the quantum mechanical behaviour of photons, the fundamental particles of light, to enable highly secure transmission of data beyond that achievable by classical encryption.

The photons themselves are used to distribute keys that enable access to encrypted information, such as a confidential video file that, say, a bank wishes to keep completely confidential, which can be sent along practical communication lines, made of fibre optics. Quantum indeterminacy, the quantum mechanics dictum which states that measuring an unknown quantum state will change it, means that the key information cannot be accessed by a third party without corrupting it beyond recovery and therefore making the act of hacking futile.

While other detectors can offer a key rate close to that reported in this journal paper, the present advance only relies on practical components for high speed photon detection, which has previously required either cryogenic cooling or highly technical optical setups, to make quantum key distribution much more user-friendly.

Using an attenuated (weakened) laser as a light source and a compact detector (semiconductor avalanche photodiodes), the researchers have introduced a decoy protocol for guarding against intruder attacks that would confuse with erroneous information all but the sophisticated, compact detector developed by the researchers.

As the researchers write, “With the present advances, we believe quantum key distribution is now practical for realising high band-width information-theoretically secure communication.”

Governments, banks and large businesses who fear the leaking of sensitive information will, no doubt, be watching closely.



August 1, 2008

Quantum cryptography news …

… from PhysOrg.com and Siemens:

Electronic communication is becoming more secure all over the world. Siemens IT Solutions and Services, Austrian Research Centers (ARC) and Graz University of Technology have joined forces to develop the first quantum cryptography chip for commercial use. The chip, which protects data by generating a completely random sequence of numbers from particles of light, replaces the currently used system of key distribution based on mathematical algorithms.

The prototype of the quantum cryptography chip is already available, and the corresponding fiber-optic network for absolutely safe, chip-based data transfer will be presented in October 2008 at Siemens IT Solutions and Services in Vienna.

This is how it works. Quantum cryptography works with individual light particles known as photons, which are generated and coded by an optical array. The security of the data is guaranteed by laws of nature, as photons generate completely random keys. The mathematical formulae used in the past, which could be decrypted with enough time and effort, will soon be a thing of the past.

Once the optical array has sent the light particles to the recipient via fiber-optic cable, each communication partner uses a detector to measure certain properties of the photons. The values are then compared using a communication protocol via the internet. If they match, the chip takes over the processing and uses the results of the measurements to generate a tap-proof

June 11, 2008

Quantum cryptography

Move over one-time pad, there’s a new kid on the cryptographic block — quantum cryptography. This is one amazing application for the weirdness that is quantum mechanics and quantum effects. And one cool way to transmit secret messages.

Today’s KurzweilAI.net newsletter had a link to a Scientific American story on space-based quantum codes used for cryptography.

Over at Bad Astronomy, Phil Plait wrote about this on Monday. He offers a cool short-version explanation of the quantum mechanics involved, and his comment section has even more detail provided by BABlog readers.

Here’s the KurzweilAI  short:

Space Station Could Beam Secret Quantum Codes by 2014
ScientificAmerican.com, June 9, 2008

University of Vienna researchers hope to send an experiment to the International SpaceStation (ISS) by the middle of the next decade that would pave the way for transcontinental transmission of secret messages encoded using quantum entanglement.

(European Space Agency

In addition to potential use for secure communications, the “Space-QUEST” project would give researchers a chance to test the theory that entanglement should be unlimited in range.

Read Original Article>>


Here’s an excerpt from the Scientific American link found above at “Read Original Article”:

Researchers hope to send an experiment to the International Space Station (ISS) by the middle of the next decade that would pave the way for transcontinental transmission of secret messages encoded using the mysterious quantum property of entanglement.

When two particles such as photons are born from the same event, they emerge entangled, meaning they can communicate instantaneously no matter how far apart they are. Transmitting entangled pairs of photons reliably is the backbone of so-called quantum key distribution—procedures for converting those pairs into potentially unbreakable codes. Quantum cryptography, as it is known, could appeal to banks, covert government agencies and the military, and was tested in a 2007 Swiss election

Here’s some of Phil Plait’s commentary at Bad Astronomy:

So some European scientists came up with the idea of using the International Space Station (I know! Using ISS for science! Wow!) to test this out. They can create a small setup with a laser which can create entangled photons. The entangled photons are then sent simultaneously to two different ground stations, widely separated on the surface of the Earth, so that both have a copy of the entangled photons. In addition, two quantum keys are created based on the photons; this is essentially a code based on the state of the photons — like winning a bet is based on which way a coin lands. The two keys are different, and one each is sent to the two ground stations. So both stations have a pair of entangled photons (identical to the other station’s) and a different key.

Each key is actually a long chain of 1s and 0s. The two keys are then compared on the ISS to create what’s called a bitwise XOR — for example, if two coins both land heads then the XOR operation yields a 0, but if they land differently (one heads and one tails) then it yields a 1 — it’s just telling you whether they are the same or different. So for each place in the key, the two numbers are compared, and if they’re the same (both 1s or both 0s) then a 0 is written down. If they are different then a 1 is put there. When this is done, you get a third string of 1s and 0s, representing a comparison of the two keys.

Still with me? Yeah, me neither, but we’re almost done. So now the ISS has this long number string which represents whether the keys are alike or different. It then transmits this to one of the two stations on Earth.

So? What does this mean? This means that now the two ground stations can create a code between them based on their keys, a code that is known only to them and no one else. Furthermore, this code cannot be cracked by anyone, anywhere, because it’s based on entangled photons that cannot be known to anyone else! Because of entanglement, they know what the other station has because they can look at their key and figure it out. But no one else can.

April 7, 2008

Supercomputing news

Two bits from KurzweilAI.net. First is a qutrit breakthrough making strides toward quantum computing.

The second is on a DARPA challenge for research projects offering “dramatic improvements” in areas including quantum computing.

Qutrit breakthrough brings quantum computers closer
Physics arXiv blog, April 4, 2008University of Queensland scientists have built and tested quantum logic gates that are vastly more powerful than those that have gone before by exploiting the higher dimensions available in quantum mechanics.For example, a qubit can be encoded in a photon‘s polarization. But a photon has other dimensions which can also be used to carry information, such as its arrival time, photon number or frequency. By exploiting these, a photon can easily be used as a much more powerful three level system called a qutrit.That allows a dramatic reduction in the number of gates necessary to perform a specific task. Using only three of the higher-dimension logic gates, the team has built and tested a Toffoli logic gate that could only have been constructed using 6 conventional logic gates. And they say that a computer made up of 50 conventional quantum logic gates could be built using only 9 of theirs.

Read Original Article>>

Uncle Sam searches for a quantum leap
NewScientist news service, April 1, 2008Under its new QuEST (Quantum Entanglement Science and Technology) program, DARPA has issued a request for proposal for research projects that address “”dramatic improvements” in “the nature, establishment, control, or transport of multi-qubit entanglement.”Applications might include parallel computing power in a quantum computer and secure communications using quantum cryptography
Read Original Article>>

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