Thursday, April 16, 2015

New Approach to Quantum Computing, Based on Braided Quasi-Particles

Quantum computing: 1 step closer with defect-free logic gate

Developing a new approach to quantum computing, based on braided quasi-particles as a logic gate to speed up computing, first requires understanding the potential error-inducing factors

What does hair styling have in common with quantum computing? The braiding pattern has inspired scientists as a potential new approach to quantum calculation. The idea is to rely on a network of intersecting chains, or nanowires, containing two-dimensional quasi-particles. The way these quasi-particles evolve in space time produces a braid-like pattern. These braids could then be used as the logic gate that provides the logical function required for calculations in computers. Due to their tight assembly, such braids are much more difficult to destabilise and less error-prone. Yet, local defects can still arise along nanowires. In a study published in EPJB, Jelena Klinovaja from the University of Basel, and Daniel Loss from Harvard University, Cambridge, MA, USA, identify the potential sources of computer errors arising from these defects.

Scientists have now created a 2D network of intersecting nanowires within which quasi particles create braided patterns in space time; these are called Majorana Bound States, or MBSs. In this context, the electrons' inner degree of freedom, called spin, interacts with their own movement, leading to spin-orbit interaction (SOI). The trouble is that the SOI direction is not uniform in such braided networks, resulting in local defects along nanowires and at nanowire junctions.

The authors therefore focus on how such defects arise in relation to the SOI direction. They show that the nanowires, in which the SOI changes direction, host novel states referred to as Fermionic Bound States (FBSs). These FBSs, the study shows, occur simultaneously with Majorana fermions, albeit at different locations in the network. FBSs could therefore destabilise quantum information units, or qubits, and accelerate their loss of coherence, thus becoming a source of errors in quantum computing. The authors believe that such new knowledge of the characteristics of FBSs can help identify the best remedy to avoid their negative effects on MBSs.


J. Klinovaja and D. Loss (2015), Fermionic and Majorana Bound States in Hybrid Nanowires with Non-Uniform Spin-Orbit Interaction, Eur. Phys. J. B 88: 62, DOI: 10.1140/epjb/e2015-50882-2

News Release Source : Quantum computing: 1 step closer with defect-free logic gate

Monday, April 13, 2015

Data Structures Influence Speed of Quantum Search in Unexpected Ways

Data Structures Influence Speed of Quantum Search in Unexpected Ways

Highly connected structures don’t always support fastest quantum computing

Using the quantum property of superposition, quantum computers will be able to find target items within large piles of data far faster than conventional computers ever could. But the speed of the search will likely depend on the structure of the data.

[caption id="attachment_572" align="aligncenter" width="600"]Data Structures Influence Speed of Quantum Search in Unexpected Ways Data Structures Influence Speed of Quantum Search in Unexpected Ways[/caption]

Such a search would proceed as a quantum particle jumps from one node of a connected set of data to another. Intuition says that the search would be fastest in a highly connected database.

“Say we are searching for a particular cafe in a city. How quickly we find it can depends on the layout of the city and the location of the cafe within the city. We might imagine that the more connected the city is, the easier it is to move around, and the easier it is to find the cafe,” said Tom Wong, one of the authors of a new analysis of the speed of such a search on databases with different structures and degrees of connectivity.

In a paper published by Physical Review Letters March 18, David Meyer, a professor of mathematics at the University of California, San Diego, and Wong, who recently earned a Ph.D. in physics from UC San Diego and is now at the University of Latvia, showed that this logic doesn’t hold for quantum computing.

“We turned an intuition on its head,” Wong said. “Searching with a quantum particle, we showed the opposite, giving an example where searching in a city with low connectivity yields fast search, and an example where searching in a city with high connectivity yields slow search. Thus the quantum world is much richer than our classical intuitions might lead us to believe.”

News Release Source : Data Structures Influence Speed of Quantum Search in Unexpected Ways

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Saturday, April 11, 2015

Bristol Quantum Information Technologies Workshop 2015

Bristol Quantum Information Technologies Workshop 2015

The Centre for Quantum Photonics is pleased to announce the return of the Bristol Quantum Information Technologies Workshop from the 15th - 17th April 2015.

[caption id="attachment_568" align="aligncenter" width="625"]Bristol Quantum Information Technologies Workshop 2015 Bristol Quantum Information Technologies Workshop 2015[/caption]

Bristol Quantum Information Technologies Workshop began in 2014 as part of a roadmap sponsored by the UK's Defence Science and Technology Laboratory and organised by the Centre for Quantum Photonics at the University of Bristol.We held our first meeting in February 2014 at Engineer's House, Bristol. The event proved to be a great success with nearly 90 delegates from around the globe all coming together to disucss topics such as the optical implementations of:

  • Quantum enhanced sensing/metrology

  • Quantum Computation and Simulation

  • Quantum Key Distribution and Communications

The first workshop resulted in a clear roadmap of the future for the quantum technologies. This year we want to go further to explore the changes in the quantum climate and further discuss the Quantum Technologies Revolution.

For more information about BQIT:15 or to register to attend please go to theconference website.

News Release Source : Bristol Quantum Information Technologies Workshop 2015

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Friday, April 10, 2015

Quantum Ghosts are Helpful for Future Quantum Technologies

Quantum ghosts are helpful

Physical Review Letters paper


The idea that far distant particles can somehow 'talk' to each other worried Einstein so much that he called it 'spooky action at a distance'.

[caption id="attachment_561" align="aligncenter" width="500"]Quantum Ghosts are Helpful for Future Quantum Technologies Quantum Ghosts are Helpful for Future Quantum Technologies[/caption]

Having confirmed its existence, scientists today are learning how to use this 'spooky action' as a helpful tool. Now a team of physicists at the University of Bristol and Imperial College London have harnessed this phenomenon to shed light on another unusual and previously difficult aspect of quantum physics - that of distinguishing between two similar quantum devices.

In the everyday world any process can be considered as a black box device with an input and an output; if you wish to identify the device you simply apply inputs, measure the outputs and determine what must have happened in between.

But quantum black boxes are different. Distinguishing between them is impossible using only single particle inputs because the outputs are not distinguishable: a fundamental consequence of the laws of quantum mechanics is that only very few states of a quantum particle can be reliably distinguished from one another.

The Bristol-Imperial team has shown how to get around this problem using 'spooky action'.

Anthony Laing, PhD student in the Department of Physics, who performed the study, said: "Apart from providing insight into the fundamentals of quantum physics, this work may be crucial for future quantum technologies.

"How else could a future quantum engineer build a quantum computer if they can't tell which circuits they have?"

The new findings have implications for our understanding of quantum mechanics as well as the emerging potential of quantum information science.

This work was performed in the Bristol Centre for Quantum Photonics led by Professor Jeremy O'Brien ( as part of a collaboration with Dr Terry Rudolph at Imperial College London.

The paper in Physical Review Letters is published online ahead of print, 24 April 2009,

The work was supported by the US Intelligence Advanced Research Projects Activity (IARPA), the UK Engineering and Physical Sciences Research Council (EPSRC), the UK Quantum Information Processing Interdisciplinary Collaboration (QIP IRC), and the Leverhulme Trust.

News Release Source : Quantum ghosts are helpful

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