Qutrit breakthrough brings quantum computers closer

Toffoli gate

The folks playing with quantum computers have been claiming for years that their gadgets will one day make today’s supercomputers look like quivering lumps of jelly. But so far, their computers have yet to match the calculating prowess of a 10-year old with ADHD.

The most exciting work so far has been on universal quantum logic gates, the building blocks of any computer. A number of groups have built and demonstrated these and one team even took their gates for the computing equivalent of a run round the block by factorising the number 15.

The trouble is that, to do anything useful with universal quantum gates, you need at least dozens and preferably hundreds of them, all joined together. And because of various errors and problems that creep in, that’s more or less impossible with today’s technology.

Which is why a breakthrough by an Australian group led by Andrew White at the University of Queensland is so exciting. They 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 in quantum mechanics. For example, a qubit can be encoded in a photon’s polarisation. 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.

This is how the Ozzie team have exploited the idea: during a computation, their gates convert qubits into qutrits, process the quantum information in this more powerful form and then convert it back into qubits. All using plain old vanilla optics.

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.

That’s a significant reduction. What’s more, they reckon that these kinds of numbers are possible with today’s linear optics technology.

That means these guys are right now bent over an optical bench with screwdrivers and lens cloths at the ready, attempting to build the world’s most powerful quantum computer. We may see the results–a decent factorisation perhaps–within months.

Could it be that Australia is about to become the center of the quantum computing world?

Ref: arxiv.org/abs/0804.0272: Quantum Computing using Shortcuts through Higher Dimensions

11 Responses to “Qutrit breakthrough brings quantum computers closer”

  1. […] Un nuevo avance en computación cuántica: de qubits a qutrits [Eng.]arxivblog.com/?p=346 por JanSmite hace pocos segundos […]

  2. I am just doing my job….why and how ….good question

  3. matter structure just tell me how WAVE FUNCTION connected

    or how wave-function will switch,some were

    I feel like
    I have to explain my purposes
    usually I deal with paper,book ,the best updated source
    but never I was dealing with human interactive knowledge

    I never explained my motivation,my dream
    all my life a cheat and shop my need
    brook some theory and fit the bad part into some dream

    now I realize with human who fairly show their purposes,dream

  4. when I saw the door
    wide open LORENTZ puzzzzzzz
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    long time ago,but just
    by my self
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    a start
    a basic skeleton,

    for me it is the out put
    with basic trig,
    I will slowly build a strength
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    and after I will shade

    I am not their for a break trough
    I shop and take what I need for complete the other half of my BOX

    I look for some of my paper as a honest sharing
    just for the BOX I have a quarter ton,ton;s

    why the boundary I will share
    it is because I do not have a spot of moral on my soul
    but JUSTICE belong to my nature

    I was stimulated and all of you honest giving their whole stuff
    with honesty
    permit to a cheater me to get a start again

    I was truly connected with the meaning of NATURE
    and I found a basic trig,as my start
    nobody understand nature
    but history prove all TIME

    evolution belong to basic observation
    manipulating basic data from an other dimension
    base on simple in put, out put,
    able us to shade the unknown

    and today I get some major change in my life
    I will not be retired anymore
    I will go back into society
    this is scary and challenging

    my dream it is to see my BOX
    but I did elementary stats
    if I do not exchange I will die
    and no dream

    imaginary ZERO real
    but first general relativity,quantum mechanic and physic
    special relativity,electromagnetic field
    EUCLIDE geometry


    thermal condition as a control of the expansion or the boundary
    space [(Ai=B) tan (A=Bi)] -dimension^time

    tan=0=(number of dimension)^0

    past now future

    now=transition momentum

    t=(t+ a=t-b) 100 1g 15g

    subatomic particle Thomson “s atomic model
    element that exists alone or in combination
    traveling from your frame of reference at the normal physical level down into the inside of matter

    vacuum fluctuation this is a fun part,the door
    energy some stuff happen between,or in between,or just we do not know but after mass exist shortly,or relatively short for us
    zero point exact will not be possible I believe because vacuum fluctuation mean what it mean
    e^-iHt COHI(c+ib)=COHI(eît(c+ib)) Beethoven

    but for math my understanding 2 dim vector,scalar,x,y,z the behavior of vector in physic enhance the math vector……this make me believe everything is relative…….it is possible and it is not possible it is just simply relative.

    c=wavelength time frequency……I will ad vibration seem to be an obvious introduction of a new cricket pitcher ….his ball and his pitch will give known data and finally some secret will be shade.

    their is no relationship from our experience
    mistake are bound to happen
    outside the range of are limit

    theory suppose the true that it is not it happen
    me I just do that I suppose all time
    and if I decide just like that to be an ass hole and suddenly spit on what I was beleiving
    I am free

    They all do the same,all

    what will be the power of my gradian
    I will not use scale,I correct
    fixing distance between each known and each unknown

    poetry that scan has a correct regular pattern
    the pain sweep over me
    as a cruel distance between 2 point of energy
    always tell me where I am,LOVE
    but it seem always the opposite direction

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    now it appear and magically
    your love disappear

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    wait until a later time my love
    time as pass and our delay of love

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    my past tense ,your immediate present time

    I keep hitting your delight
    regularly when I imagine your curve
    your breast description
    allow me to pass on a longer note philippe martin

  5. Tamir Boaz says:

    Well done !!!!

    This is what Knuth was suggesting a long time ago !!! He called those gates Flip-Flap-Flop.


  6. Paul foster says:

    What is wrong with a 10 year old with ADHD? Could you not find a less insulting comparision?

  7. D. Troyer says:

    Many thought Galleo was insane or a heritic with his truths and theorys of which many are fact in our society today. I would like to know the HOW and WHY too, but knowing how this WORLD works in it’s greed and quest for power, it may be best to know the HOW and WHY after the computer is built. I am sorry but the jebberish in a previous response would mean absolutely nothing to most people in this world. I believe in a concise and straight forward answer, like, “they are crazy to think… “ or something to the that nature in the positive. I, myself, could not make heads or tails of what was spoken by Phillipe. I guess I am not on the same WAVELENGTH or QUANTUM PARTICLE. All I ask, Phillipe, explain in “plain english” what you are trying to say?! I applaud the Austrailian team on their break-through and hope they make “GOOD” on their discovery soon.

  8. […] the physics arXiv blog » Blog Archive » Qutrit breakthrough brings quantum computers closer (tags: toread Technology quantum physics computing) […]

  9. Dave says:

    What is wrong with an abacus? Get over it and stop being such a PC nazi. I thought the ref to a 10 year old with ADHD was quite good. Hell , I was one, before they knew what it was and had the term.