During the past months we’ve been reporting several breakthroughs in the field of quantum computing, and now IBM seems ready to truly pave the way for quantum computers. Researchers announced they are now able to develop a superconducting qubit made from microfabricated silicon that maintains coherence long enough for practical computation. Whoa! That probably sounds like a lot to swallow, so let’s break it down.

Bits and Qubits

Information is measured in ‘bits’, and a bit may have two positions (described typically as 0 or 1). Quantum computers however don’t use these bits, and instead they use quantum bits, or ‘qubits’. But while a bit must be a 0 or a 1, a qubit can be both 0, 1, or a superposition of both. This difference might seem small and subtle, but in fact, it is absolutely humongous: a mere hundred qubits can store more classical ‘bit’ information than there are atoms in the Universe.

Three superconducting qubits. Credits: IBM research

Needless to say a computer running on qubits would be game changing, in pretty much the same way microprocessors were in their days. But what makes quantum computing extremely difficult is a problem called ‘decoherence‘. In the quantum world, things don’t happen as they do in the ‘real world’; when a qubit will move from the 0 state to the 1 state or to a superposition, it will decohere to state 0 due to interference from other parts of the computer. Generally speaking, decoherence is the loss order of the phase angles between the components. So in order for quantum computers to be practical and scalable, the system would have to remain coherent for a long enough time to allow error-correction techniques to function properly.

“In 1999, coherence times were about 1 nanosecond,” said IBM scientist Matthias Steffen. “Last year, coherence times were achieved for as long as 1 to 4 microseconds. With these new techniques, we’ve achieved coherence times of 10 to 100 microseconds. We need to improve that by a factor of 10 to 100 before we’re at the threshold we want to be. But considering that in the past ten years we’ve increased coherence times by a factor of 10,000, I’m not scared.”

Two different approaches, one breakthrough

IBM announced they took two different approaches, both of which played a significant part in the breakthrough they revealed. The first one was to build a 3-D qubit made from superconducting, microfabricated silicon. The main advantage here is that the equipment and know-how necessary to create this technology already exists, nothing new has to be invented, thanks to developments made by Yale researchers (for which Steffen expressed a deep admiration). Using this approach, they managed to maintain coherence for 95 microseconds – “But you could round that to 100 for the piece if you want,” Steffen joked.

The second idea involved a traditional 2-D qubit, which IBM’s scientists used to build a “Controlled NOT gate” or CNOT gate, which is a building block of quantum computing. A CNOT gate connects two qubits in such a way that the second qubit will change state if the first qubit changes its state to 1. The CNOT gate was able to produce a coherence of 10 microseconds, which is long enough to show a 95% accuracy rate – a notable improvement from the 81% accuracy rate, the highest achieved until now. Of course, the technology is still years away from being actually on the shelves, but the developments are very impressive.

From quantum to reality


Given the rapid progress that is being made in the field of quantum computing, one can only feel that a quantum computer is looking more and more like a real possibility. As error correction protocols become more accurate and coherence times grow longer, we are moving more and more towards accurate quantum computing – but you shouldn’t expect a quantum smartphone just yet.

“There’s a growing sense that a quantum computer can’t be a laptop or desktop,” said Steffen. “Quantum computers may well just being housed in a large building somewhere. It’s not going to be something that’s very portable. In terms of application, I don’t think that’s a huge detriment because they’ll be able to solve problems so much faster than traditional computers.”

The next steps are simple, in principle, but extremely hard to do in practice. The accuracy rate has to be at at least 99.99%, up to the point where it achieves what is called a ‘logical qubit’ – one that, for practical purposes, doesn’t suffer decoherence. From that point, the only thing left to do is develop the quantum computer architecture, and this will prove troublesome too – but the reward is definitely worth it.

“We are very excited about how the quantum computing field has progressed over the past ten years,” he told me. “Our team has grown significantly over past 3 years, and I look forward to seeing that team continue to grow and take quantum computing to the next level.”



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  1. 1

    This article is unfortunately a poorly written collection of half-truths and pseudoscience. It’s a shame but you really need to understand the concepts behind Quantum Physics before you try to explain to others.

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    “…can store more classical ‘bit’ information than there are atoms in the Universe.”

    The current evidence points to the universe as being infinite. As a corollary, the matter (amount of atoms) in the universe is infinite as well. Perhaps you mean observable universe? 

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     No evidence suggests the universe is infinite. The edge is currently 13-15 billion light years away.

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    provide three point of information supporting what you are saying.  also it’s said the Universe is Infinitely EXPANDING, I thought….

    and you estimate seems pretty small, I thought that was the distance to the closest star system….

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    The edge of what we can see, considering it is expanding, it’s perfectly plausible to say that there are things beyond what we can see that are either moving away faster than the speed of light, or are so far away light hasn’t been able to reach yet

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    Nope. The closest star system to the Solar system is “only” 4.37 light-years away: http://en.wikipedia.org/wiki/Alpha_centauri#Observational_history
    I don’t know about the size of the Universe though. :-/

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    In my dim understanding, the universe is big enough there are many many exact replicas of our current Hubble Volume (everything we can see, roughly 13.7 billion light years in every direction) down to the motions of every subatomic particle, and then even more slight variations, but even so, this particular universe is not infinite, it’s got a finite amount of energy.  But then most probably there are a lot of other universes, many of them identical to ours or varying in subtle or major ways, exploding from false vacuums or collisions of branes, and at that level it might well be infinite, the ultimate arena for Darwinian evolution as universes replicate like bacteria in a stupendous petri dish, and burn in rapid propagation like unbelievable bonfires, and perhaps some are managed and bred like domestic animals by the intelligent beings they have birthed.

    Whether qubits can encompass all that, I have no idea.

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    That’s an unfair comparison, I’m assuming you are trying to demonstrate that they are extremely different, but you are also implying that Quantum Physics is the same orders of magnitude more complicated than Rocket Science is to 1+1=2.  Comparing a Quantum Physicist and Rocket Scientist isn’t like comparing a Rocket Scientist and a First Grader.

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     Fair enough. The estimate for the size of the universe is based on two assumptions, one of which is integral to the big bang theory.

    1) Integral to the big bang theory is that space began in a singularity in/of space 13.7 billion years ago.

    2) Nothing travels faster than the speed of light in any frame of reference. (Some interpretations of the inflationary theory state that the inflation period of the big bang occurred faster than the speed of light; this could add an arbitrary but finite factor to the size of the universe.)

    If those two assumptions are made, and used along with the theory of relativity, it follows that the further away you look in space, the further back you look in time. Therefore, if you point a telescope at the sky, where there is nothing in the way, you will see the big bang 13.7 billion light years away. Actually, you’ll see a wall of hot hydrogen that existed a very short time after the big bang… but, close enough. This is the cosmic background radiation.

    There are other trans-dimensional big bang explanations that allow for an infinite universe, but there is no evidence yet that supports them. So, usually when you hear someone estimate the number of atoms or energy in the universe, they are estimating the number of atoms or energy in our observable sphere of radius 13.7 billion light years and growing.

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     Oops. I forgot the reference:


    Many other google links for the big bang will reliably take you to the same information.

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    Here, Lister is a physics genius capable of understanding complex quantum mechanics and easily explaining them in writing to even the most daft ludites of science.

    Out there, he is just another Starbucks employee wishing that he’d paid attention in school.

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    100 bits can store one number with a decimal value of up to 2 to the power of 100. 100 qubits can store all the numbers from 0 to 2 to the power of 100 at once. That’s a lot less than atoms in the universe.

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    This guy’s gotta be trolling. Even if we accept the premise of an infinite universe, that wouldn’t imply infinite mass.

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    100 bits can actually store a whole number (no decimal) up to 2 to the 99th. Your first bit is 1, which leaves 99 bits starting at 2 to the first.

     But what would actually take place is the arrangement of bits into bytes, so you would have either 13, bytes (for 96 bits) or 14 bytes (for 104 bits), Each set of 3 bytes would be used to make a floating point number, one byte would signify that that the value stored is to be a floating point number, one byte would be assinged an integer, and one byte would be assigned a mantissa (spellcheck?), a mantissa is effectively an exponent. Meaning you can represent a 64 bit number (16.8 trillion) with only 3 bytes.

    Now imagine the the same thing with qubits. the number is much much much higher than you suggest.

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    Instead quantum vs “real” world, a more accurate comparison would be quantum vs macroscopic.

    I just hope I’ll see one usable quantum computer in my lifetime (I should have about 50 years or so left :) ).

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    I’d still agree with the comparison, not of the Quantum Physicist and and Rocket Scientists, but of the complexity of the two fields. Rocket science in my opinion is somewhat of an outgrown cliche; the science behind the systems analysis and relevant physics is relatively well understood. This surely isn’t saying we know everything there is to know about it, just that in today’s world the study and research of quantum physics seems more complex and daunting than constructing a rocket the won’t tear itself apart at launch.

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    That’s exactly what I was thinking! Unless the use of “a superposition” in the article was a mistake on the reporter’s part, and the actual research involves multiple potential superimposed states.

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    Just jumping off some of the work of cosmologists Andrei Linde and Allen Guth, and some of the stuff from M theory. Nothing much beyond what you’d find in Scientific American, I promise. (It had a big article on multiverse theory a few years ago, where I got the stuff about Hubble Volumes).

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    Dr. Margon: “Mother Nature is having a double laugh. She’s hidden most of the matter in the universe, and hidden it in a form that can’t be seen” 

    source quote from:

    McDonald, Kim A; ”New Findings Deepen the Mystery of the Universe’s ‘Missing Mass’.” 
    Chronicle of Higher Education.

    how do weigh that which we cannot see, feel, measure etc.

    something like 90% of the mass in the universe is hidden from us. how do you claim we KNOW the weight of the ENTIRE universe, when we don’t know for certain the weight of the observable universe.

    “its not rocket science” just use your head mate, if anything the weight you would be referring to would be a great educated guess, or calculated approximation?

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