Building quantum registers from imperfect crystals

Chris Lee at Ars explains some new research that could fill in a critical piece needed for a practical quantum computer, a way of storing multiple qubits similar to a register in a classical computer so more sophisticated computation and communication can be realized. Lee does his usual excellent job of making what can be a pretty opaque topic very readable, especially how this likely informs future applications.
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Two Photon Quantum Walk Demonstrated

Slashdot links to a Gizmag article discussing some new research out of the University of Bristol.

A random walk – a mathematical concept with useful applications in computer science – is the trajectory of an object taking successive steps in a random direction, be it over a line (with only two possible directions) or over a multi-dimensional space. A quantum walk is the same concept, but translated to the world of quantum computing, a field in which randomness plays a central role. Quantum walks form an essential part of many of the algorithms that make this new kind of computation so promising, including search algorithms that will perform exponentially faster than the ones we use today.

Single photon quantum walks have been achieved before. What this group did was to overcome the difficulties of managing two photons in identical states and account for their inevitable interference. The big hurdle was increasing from one to two, the researchers are optimistic that scaling from two to any number of particles should be much easier to accomplish.

There has been a lot of questions around what quantum computing will practically do better than classical computers. This still doesn’t directly answer those questions but it is a key bit of progress towards non-trivially complex quantum computers. Once we have one that approaches the register size of even the early vacuum tube goliaths, then we should be able to start mapping out practical applications and benefits.

Two-photon walk a giant stride for quantum computing, Gizmag (via Slashdot)

feeds | grep links > D in Gnu’s Debugger, Police Raids Hit Wikileaks and Pirate Bay, Hope and Hype in Quantum Computing, and More

I am back from Dragon*Con but thoroughly wiped out. It looks like I will return to my usual blogging routine tomorrow. For now, here are some more links.

Quantum Zeno Effect May Allow Routing Qbits

One of the barriers to using quantum states for information processing is the unexpected effects of observation. Trying to figure out how to put these counter intuitive processes to work often seems insurmountable, as is the case when contemplating how to preserve the usual superposed states of qbits when the goal is to send them over a network. That superposition, the simultaneous holding of multiple states, is the biggest difference from how information is represented in classical computing. Observation ends superposition, or more properly causes it to decohere.

Technology Review explains some new research Yu-Ping Huang and colleagues at Northwestern that may make switching and routing of quantum information possible.

First a little more about the effect itself. Imagine a photon in state 0 which has a certain probability of decaying into state 1. Now carry out a series of periodic measurements on the photon. Between the measurements, the photon evolves into a superposition 0 and 1 states and a measurement will cause it collapse into one or other of these.

However, if the time between the measurements is small, the chances of it collapsing to form a 1 are smaller than the chances of it becoming a 0. And if the periodic measurements are made rapidly enough, the probability of a measurement producing a 1 tends to zero.

In effect, the process of repeated measurement prevents the photon decaying from a 0 to a 1. That’s the quantum zeno effect, sometimes also called the watched-pot-never-boils effect.

Now Huang and co have come up with a scheme that exploits this effect to create a switch. The basic idea is to take a signal wave in state 0 which will decay or evolve into a 1 when it passes it through a nonlinear waveguide.

Not only is the quantum state, the superposition, of the information carrying bit preserved with this scheme but it could offer power savings to boot. The research is still very much in the theoretical stage but is part of a larger project at DARPA. By the time quantum computers are ready to be networked together, we may just be able to do so practically.

feeds | grep links > Consumer Friendly ISP Caught Using DPI, P != NP Possibly Solved, and More

I was traveling today so apologies for the lateness of the links and the utter lack of commentary. I’ll be at a tech event all day tomorrow so not sure that I will be able to manage better until after I am done with this trip altogether.

feeds | grep links > Internet Kill Switch, Fair Use before DRM in Brazil, and More

TCLP 2010-07-11 News

This is news cast 218, an episode of The Command Line Podcast.

In the intro, thanks to new donor, Scott, and a request that existing donor Ryan contact me so I can send him his merit badge. Also, there will be new feature cast this week. I need to catch up on writing features for the show and I will be attending two events in DC this week: What Does Light Taste Like and Decoding Digital Activism.

This week’s security alerts are researchers form collective in response to Microsoft’s dismissal of a security concern and REMnux, a linux distro designed for reverse engineering malware.

In this week’s news new quantum states could lead to new approaches to quantum computing, the Apache web server conquers the world, another constructive criticism of transparency, and the NSA is looking to implement domestic surveillance of our infrastructure though they are quick to deny any active monitoring.

Following up this week, two UK ISPs are taking the Digital Economy Act to High Court.


View the detailed show notes online. You can also grab the flac encoded audio from the Internet Archive.

Creative Commons License

This work is licensed under a Creative Commons Attribution-Share Alike 3.0 United States License.

feeds | grep links > Ubuntu on a NexusOne, Google’s New System for Infringing Music, Possibilities for Scalable Quantum Computers, and More

  • Installing Ubuntu on a Nexus One
    Make has a video of the installation process from, document and demonstrated over the long weekend. It isn’t that much of a stretch as Android, the phone’s default OS, already uses a Linux kernel, just an entirely different stack on top of it. Mm, I could definitely see Ubuntu’s forthcoming Unity interface for netbooks running well on a smartphone.
  • Google’s potential new system for avoiding takedowns for infringing music copyrights
    According to Slashdot, the novel aspect of this patent application isn’t identifying potentially infringing music in YouTube videos, but a set of actions from which an uploader may be able to choose: remove the video, swap the soundtrack for something approved, or to mute the video. As the post notes, there is no allowance for use with permissions. Once again, there is also no room for no action, relying on fair use. If implemented, this rely isn’t much better than the filtering system in place now.
  • New fabrication technique could lead to scalable quantum computers
    The key, as Technology Review explains, is inducing nitrogen vacancies within a diamond crystal. The vacancies can be made to luminesce so the implication is they could be used to stored and emit photons, which have been used in other quantum computing rigs. The research hasn’t advanced that far, it really is more about the fabrication technique but the potential is fascinating.
  • Blizzard to require real names to post on its forums

feeds | grep links > Clarification on New Quantum Computing Research, Intelligence Analyst Arrest over Claims of Leaks, and Australian Police Want to Deputize Facebook

  • Clarifying coverage of paper eroding quantum computing
    Scott Aaronson has a must read post if you follow quantum computing as I do, in particular the Ars post on a paper that proposes to undermine one possible advantage of quantum computing. In a nutshell, what the paper shows is much more limited than Chris Lee made out, in particular the findings do not necessarily apply to all models or approaches to quantumcomputing.
  • Intelligence analyst arrested over claims he leaked video to WikiLeaks
    I debated not remarking on this and still feel that there isn’t anything particularly interesting here, despite the supposed role of WikiLeaks and Adrian Lamo. Manning clearly made a huge mistake outing himself as a source of leaks and arguably an even bigger one violating the trust placed in him as a member of themilitary.
  • Australian police want to deputize Facebook
    I have to agree with Curt Hopkins in his conclusion in this RWW post. It is enough that companies not break local laws, this is asking to much, that Facebook play an active role in reporting crime and enforcing local laws. Does anyone know if the Australian police have tried this before, by way of context, with Facebook or any other such service?

TCLP 2010-06-06 News

This is news cast 215, an episode of The Command Line Podcast.

In the intro, just a pointer to my thoughts on Balticon 44 and a recap on advertising, the badge experiment, and Flattr so far.

This week’s security alerts are OS choice does not equal security and an Android rootkit.

In this week’s news Google drops Microsoft for internal use citing security reasons though some are skeptical, figuring out if Wikileaks spun up using documents intercepted from Tor with thoughts from both the Tor project and Wikileaks itself, IBM’s 40 year old Muppet sales films, and a new paper debunks certain suggested advantages of quantum computing.

Following up this week, if you are tired of Facebook then check out a Firefox extension that aims to help preserve your privacy while using it and India tries to gather opposition to ACTA.


Grab the detailed show notes with time offsets and additional links either as PDF or OPML. You can also grab the flac encoded audio from the Internet Archive.

Creative Commons License

This work is licensed under a Creative Commons Attribution-Share Alike 3.0 United States License.