And yes, Scotland will be there, in the form of Professor Catrina Bryce (right) from Glasgow University Department of Electronics and Electrical Engineering, who is program co-chair in the science and innovation fields.

The Technology transfer session looks to be a small gold mine, with speakers sourced from Sandia National Labs, Stanford University, Optical Science division of Naval Research Lab, Princeton University & Sydor Instruments, as BioPhotonic Solutions Inc, CeLight Lincoln Laboratory, MIT NuCrypt LLC and Sentinel Photonics are all talking license-ready technologies.

Quantum correlated atoms in atom-chip
Objects well separated in space but that still cannot be understood separately,  are the profoundest quantum physics oddity.

Photon pairs are prominent examples of such systems. They allow the teleportation of quantum states or 'tap-proof' data transfer using quantum cryptography.

Such experiments will not be restricted to photons in the future, as Vienna University of Technology has developed a method to create correlated atom pairs using ultracold Bose-Einstein condensates with the experiment results published in Nature Physics.

Even Einstein apparently did not like the idea of well separated particles still being quantum mechanically connected, calling the phenomenon “spooky action at a distance.”

However the quantum theory predictions have been verified in countless experiments. Quantum particles can, even far apart, still belong together and “share” certain physical properties.

“This does not mean by manipulating one particle we can at the same time change the other, as if they were connected by an invisible thread,” says Professor Jörg Schmiedmayer (TU Vienna) says, “but still, we have to treat both particles as one single quantum system – and that opens the door to fascinating new experiments.”

His team at the Institute for Atomic & Subatomic Physics, carried out the experiments, while theoretical calculations were done at Karl Franzens University, Graz, Austria by Ulrich Hohensteiner.



Conservation of Energy and Momentum 


In order to produce the quantum-correlated atoms, researchers first create a Bose-Einstein condensate.

This exotic state of matter occurs at less than a millionth of a degree above absolute zero. Atoms in Bose-Einstein condensate are in the lowest possible energy state. “The key to success are our atom chips,” explains Thorsten Schumm (TU Vienna).

With perfectly tailored chip structures, atoms can be manipulated with incredible precision. It is possible to deliver single quanta of vibrational energy to the atoms of the ultracold Bose-Einstein condensate. When the atoms return to the lowest energy state, the condensate has to get rid of the surplus energy.

“Because of the sophisticated design of our atomchips, the Bose-Einstein condensate is left with only one single way to dispose of its energy: emitting pairs of atoms. All other possibilities are forbidden by quantum mechanics,” explains Robert Bücker.

According to the law of momentum conservation, the two atoms move in exactly opposite directions. This process is closely related to effects in special optical crystals, in which pairs of photons can be created (so-called “optical parametric oscillators”) but now instead of light, massive particles can be used.



The emitted twin atoms cannot be understood in the same way as classical particles, as debris scattered in all directions in an explosion. They are quantum mechanical copies of each other and only differ by their direction of motion. They form one common quantum object. One atom cannot be mathematically described without also describing the other.

“We are going to use these atoms for exciting new experiments," Schmiedmayer enthuses. “A fascinating new field of research is opening up from which new insights and possible applications will evolve. 

"It is conceivable that these correlated atom beams will lead to new quantum measurement methods, with a precision far beyond the scope of classical physics.”

Australia with UK and France
L:R CUDOS researcher Chunle Xiong holding the new (small) and old (big) chip, Ben Eggleton, & Christian Grill
Australian researchers develop an on-chip, microscale photon-pair emitter, that could yield complex devices for future quantum applications.

The research was part of the Centre of Excellence for Ultrahigh Bandwidth Devices for Optical Systems' (CUDOS) Quantum Integrated Photonics project aimed to develop a chip capable of both generating photons and performing logic operations within five years.

With collaborators UK and French collaborators, the CUDOS team demonstrated an 80-micron-long emitter of correlated photon pairs – 100 times smaller than devices used by other groups.

CUDOS director Ben Eggleton explained that the device could be one way of generating qubits for future quantum cryptographic and computing applications. “There’s an international race to create the building blocks of these quantum technologies,” he said.

The ‘photonic crystal waveguide’ fabricated on silicon chip is expected to be scalable and compatible with current manufacturing techniques. The team’s research paper, to be presented in Baltimore, USA , says photons generated by the device would be routed for use in quantum logic gates or communication protocols.

Eggleton explains the device took a statistical approach to qubit generation, in contrast to smaller, single-photon-generating quantum dots. Its size was achieved by slowing light that passed through the device by a factor of 20 to 30, increasing non-linear effects of the waveguide.

Researchers accordingly expect the size of the device to allow hundreds to be incorporated into a single chip. Next to enabling use in ‘unhackable’ quantum key distribution networks is to create entangled photons, says Eggleton.

While the quantum information market is “not a huge one at the moment”, he said, CUDOS researchers would collaborate with organisations like the Sydney University’s upcoming Institute of Nanoscience on fabrication and manufacturing techniques.

Eggleton also hoped to combine the emitter with research by University of Bristol professor Jeremy O’Brien (right) who in 2009 demonstrated a quantum logic circuit that could factorise the number 15, with incredibly quick scaling.

The three-month-old CUDOS project is on track to deliver the “world’s first chip-based quantum information device” within five years.

Single atom quantum information storage
Quantum information encoded in weak light pulses, consisting of single photons is transferred onto a single rubidium atom.

There, the information is stored for some time and retrieved later by producing a single photon. Image courtesy of Andreas Neuzner, MPQ

Scientists in the group of Professor Gerhard Rempe, (director, Max Planck Institute of Quantum Optics and head of Quantum Dynamics division) have succeeded in transferring quantum information encoded in a single photon onto a single atom. There the information is stored for some time and later retrieved.

“This provides us with a universal node for a quantum network,” Rempe points out. The experiment opens up new perspectives for development of scalable quantum networks in which photons communicate quantum information between several nodes over long distances.

Ongoing miniaturisation of chip structures used for information storage has reached the limits classical laws of physics can no longer be applied. Instead, the systems are ruled by the laws of quantum mechanics.

In this physical limit, the smallest storage device consists of a single atom, the smallest possible unit for optical data transfer is a single photon. The special properties of these quantum particles can thus be used to engineer novel applications, eg. quantum cryptography devices or gates to process quantum information. Implementing such new technologies requires new concepts for information transfer and storage.

The most promising candidate is the implementation of a network of distributed quantum memories communicating with each other via exchange of photons. Development requires two main realisations.

The transfer of quantum information stored from memory node onto a single photon, was demonstrated a couple of years ago in by the  division with the implementation of a single-photon-emitter based on a single atom.

And the writing of a photonic qubit into another stationary quantum memory and its retrieval without significant distortion, so far only fulfilled by experiments using ensembles of thousands of particles, information being mapped onto a shared atomic excitation.

In order to take full advantage of opportunities provided by quantum mechanics in practical implementations, eg. quantum computers, it would be best to exchange information between single particles of both light and matter, that can directly be addressed and manipulated.

In this experiment, a single rubidium atom is employed as a quantum memory for the first time. In order to increase its weak coupling to a single photon, the atom is trapped inside an optical resonator consisting of two highly reflecting mirrors. It is kept in place with laser light. The incoming photon is reflected back and forth between two mirrors around 20 000 times.

The quantum information stored in the photon has to be written onto the atom. “While a classical bit represents unambiguously one of two possible values – 0 or 1 –, a quantum bit is a coherent superposition of two quantum states," explains Dr Holger Specht explains.

“We therefore encode the information using a coherent superposition of two polarisation states of the photon, eg. right- and left-handed polarisation.

"The transfer of optical quantum information is enabled by a so-called control laser: when both the photonic qubit and control laser are present, the atom makes a transition into a state which is – and this is the trick – a coherent superposition of two sub-states.

The relative amounts of the two sub-states correspond to the respective amounts of the two polarisation states of the input-photon. After a variable storage time, read-out of the quantum information is initiated by the control laser as well. The whole process is reversed and the photonic qubit released, with an average efficiency of about 10%.

In a series of measurements using different input polarisation states,  fidelity between the original and read out photons turned out to be higher than 90% in all cases.

“The fidelity with the input photon that we achieve with our new method is much better than would be possible with any kind of classical measurement device,” says doctoral student, Christian Nölleke.

Considering the achieved storage efficiency and fidelity, the system is comparable to the best quantum memories available worldwide, the difference that its “hardware” consists of only a single atom. Simultaneously it provides storage times of about 200 microseconds which exceeds all values achieved with optical memories so far.

“There is still room for improving fidelity and storage times by optimising the experimental conditions,” Dr Stephan Ritter points out.

Scientists now plan to use the system to demonstrate a basic quantum network of two communicating nodes. Because of its universal properties, the quantum memory demonstrated here is a cornerstone for the development of optical quantum gates and quantum repeaters.

These  are fundamental requirements for processing of quantum information in a quantum computer and the implementation of long distance quantum communication.

Bringing diamond to networks
Researchers at University of Calgary and Hewlett Packard Labs in Palo Alto, California, have emerged with a way to use impurities in diamonds as a method of creating a node in a quantum network.

In addition to making powerful and secure networks, this  may also help sensitive measurements of magnetic fields and create new powerful platforms useful for applications in biology.

“Impurities in diamonds have recently been used to store information encoded onto their quantum state, which can be controlled and read out using light. But coming up with robust way to create connections needed to pass on signals between these impurities is difficult,” says Dr Paul Barclay, who recently moved to Calgary to start labs at University of Calgary in the Institute for Quantum Information Science and at the National Institute for Nanotechnology in Edmonton.

“We have taken an important step towards achieving this,” adds Barclay.

Impurities in diamonds (left) are responsible for slightly altering the material’s colour, typically adding a slight red or yellow tint.

The “NV center” impurity, which consists of a nitrogen atom and a vacancy in otherwise perfect diamond carbon lattice, has quantum properties that researchers are learning to exploit for useful applications.

In principle, individual photons, can be used to transfer this quantum information between impurities, each of which could be a node in a quantum network used for energy efficient and powerful information processing.

In practice, this is challenging to demonstrate because of the small size of impurities (a few nanometers) and the experimental complexity that comes with studying and controlling several nanoscale quantum systems at once.

Researchers at Hewlett Packard Labs and Barclay, who worked on this research at HP and is now a professor in  Department on Physics and Astronomy, have created photonic 'microring resonators' on diamond chips.

Microrings are designed to efficiently channel light between diamond impurities, and an on-chip photonic circuit connected to quantum impurities at other locations on the chip. In future work, the microring will connect to other components on the diamond chip, light being routed between impurities.

“This work demonstrates important connections between fundamental physics, blue sky applications, and near- term problem solving.

"It involves many of the same concepts being pushed by companies such as HP, IBM, and Intel who are beginning to integrate photonics with computer hardware to increase performance and reduce the major heat generation problem,” says Barclay.

Resonant enhancement of the zero-phonon emission from a colour centre in a diamond cavity, Andrei Faraon, Kai-Mei Fu, Charles Santori and Ray Beausoleil (Hewlett Packard) and Paul Barclay (Hewlett Packard University of Calgary), published in Nature Photonics.