Quantum photonic computers

A dramatic practical application of “weird science” may revolutionize computers in the next five years:

A new photonic chip that works on light rather than electricity has been built by an international research team, paving the way for the production of ultra-fast quantum computers with capabilities far beyond today’s devices.

Future quantum computers will, for example, be able to pull important information out of the biggest databases almost instantaneously. As the amount of electronic data stored worldwide grows exponentially, the technology will make it easier for people to search with precision for what they want.

An early application will be to investigate and design complex molecules, such as new drugs and other materials, that cannot be simulated with ordinary computers. More general consumer applications should follow.

Jeremy O’Brien, director of the UK’s Centre for Quantum Photonics, who led the project, said many people in the field had believed a functional quantum computer would not be a reality for at least 25 years.

“However, we can say with real confidence that, using our new technique, a quantum computer could, within five years, be performing calculations that are outside the capabilities of conventional computers,” he told the British Science Festival, as he presented the research.

The breakthrough, published today in the journal Science, means data can be processed according to the counterintuitive rules of quantum physics that allow individual subatomic particles to be in several places at the same time.

From a sidebar:

Why quantum computing?

To make use of properties that emerge on an ultra-small scale. “Entanglement” – the ability of subatomic particles to influence one another at a distance – and “superposition” – the fact that a particle does not have a definite location and can be in several places at once – are the two most important properties.

Yes, it’s weird but why is it useful?

Because quantum particles can do very many things at the same time, unlike an electronic “bit” in conventional computing. The use of quantum particles, or “qubits”, permits parallel computing on a scale that would not be possible with conventional electronics.

What particles are you talking about?

Many scientists are working with atoms or ions trapped in ultra-cold conditions. But the latest discovery by the Bristol-led team uses photons – light particles.

How does a quantum chip actually work?

There are several models. The Bristol version sends “entangled” photons down networks of circuits in a silicon chip. The particles perform a co-ordinated “quantum walk”, whose outcome represents the results of a calculation.

via FT.com / Global Economy – Computers set for quantum leap.

About Gene Veith

Professor of Literature at Patrick Henry College, the Director of the Cranach Institute at Concordia Theological Seminary, a columnist for World Magazine and TableTalk, and the author of 18 books on different facets of Christianity & Culture.

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  • Carl Vehse

    And on September 16, 1954, Lewis L. Strauss, then Chairman of the Atomic Energy Commission, told the National Association of Science Writers in New York: “It is not too much to expect that our children will enjoy in their homes electricity too cheap to meter.”

  • Carl Vehse

    And on September 16, 1954, Lewis L. Strauss, then Chairman of the Atomic Energy Commission, told the National Association of Science Writers in New York: “It is not too much to expect that our children will enjoy in their homes electricity too cheap to meter.”

  • Bryan Lindemood

    The behavior of light and the subatomic is crazy cool. But why does it behave this way?

    “the fact that a particle does not have a definite location and can be in several places at once”

    Can anyone point me to some links to some plausible explanations? I’m interested in reading more about this.

  • Bryan Lindemood

    The behavior of light and the subatomic is crazy cool. But why does it behave this way?

    “the fact that a particle does not have a definite location and can be in several places at once”

    Can anyone point me to some links to some plausible explanations? I’m interested in reading more about this.

  • Digital

    Carl@1
    Which would have been the case had we not been scared witless of atomic energy by a couple snafus. We are finally getting back to nuclear power plants…over 56 years later.
    Bryan@2
    It is a fascinating subject, very difficult to explain in a forum, I suggest you start with Wikipedia articles on Quantum Physics. I have been anxiously awaiting them since I read up on organic and quantum processors back in 2000.

  • Digital

    Carl@1
    Which would have been the case had we not been scared witless of atomic energy by a couple snafus. We are finally getting back to nuclear power plants…over 56 years later.
    Bryan@2
    It is a fascinating subject, very difficult to explain in a forum, I suggest you start with Wikipedia articles on Quantum Physics. I have been anxiously awaiting them since I read up on organic and quantum processors back in 2000.

  • http://www.redeemedrambling.blogspot.com/ John

    Bryan: google “double slit experiment” or “Tonimura et al”

  • http://www.redeemedrambling.blogspot.com/ John

    Bryan: google “double slit experiment” or “Tonimura et al”

  • nqb

    Bryan, the double slit experiment is exactly what I would suggest as an “explanation” of quantum mechanics. But I warn you, you won’t find an explanation but rather an experiment that has only successfully been explained with the ideas of quantum mechanics. Once you have accepted “yes, these are real phenomena and, yes, this quantum description is the only satisfactory explanation,” you can look at how our macroscopic world emerges from all this quantum behavior. This connection is really what makes it all “plausible” (moreoever, true) to me.

  • nqb

    Bryan, the double slit experiment is exactly what I would suggest as an “explanation” of quantum mechanics. But I warn you, you won’t find an explanation but rather an experiment that has only successfully been explained with the ideas of quantum mechanics. Once you have accepted “yes, these are real phenomena and, yes, this quantum description is the only satisfactory explanation,” you can look at how our macroscopic world emerges from all this quantum behavior. This connection is really what makes it all “plausible” (moreoever, true) to me.

  • Ryan

    It’ll be just like Star Trek!

  • Ryan

    It’ll be just like Star Trek!

  • bunnycatch3r

    Do the varying results of the double slit experiment mean that ideas/arguments don’t have to be logical or rational to be true? And if physical reality turns out to be subjective does that mean truth is subjective?

  • bunnycatch3r

    Do the varying results of the double slit experiment mean that ideas/arguments don’t have to be logical or rational to be true? And if physical reality turns out to be subjective does that mean truth is subjective?

  • http://theeternaluniverse.blogspot.com/ Joseph Smidt

    I hope quantum computing works out as it has some real revolutionary benefits. Unfortunately there are still a lot of skeptics. Things like this make me hopeful.

  • http://theeternaluniverse.blogspot.com/ Joseph Smidt

    I hope quantum computing works out as it has some real revolutionary benefits. Unfortunately there are still a lot of skeptics. Things like this make me hopeful.

  • WebMonk

    Like nqb said, it’ll drive you nuts if you try to think of how it can be in two places at once. The double-slit phenomena is real, as are a multitude of other effects. I’m not 100% sure we know truly what is going on, but we have figured out an EXTREMELY good way of understanding it, so maybe that understanding is really what is going on.

    Basically, light (and everything) exists as a probability wave – every proton in your body doesn’t exist as a solid thing, it exists as a probability of being in the carbon atom making up one of your DNA sequences. The probability of it being there is very high, but not 100%. It exists at a variety of different locations, but the probability of it being located in that carbon atom is huge while the probability of it existing a couple cm away is minuscule (but not zero).

    Piece of background: if you see a water wave going through two slits, it will go through them both and diffract through them, making a light and dark pattern on the other side as the wave has been split into two and interact with each other.

    That’s an effect we can see with the double-slit experiment – an experimenter sends a single photon of light or a single electron at material with two tiny slits in it. The single photon hits a receptor on the other side as a single photon, diffracted off in some direction.

    Send in another photon an hour later, and you can see it’s impact on the receptor, diffracted off in a different direction. Solid particles moving through slits aren’t diffracted, only waves are diffracted. However, when the electron or photon is sensed on the other side, it has been diffracted (a wave) but makes a single dot on the receptor (particle).

    Not only that, but if you feed lots and lots of single particles (photons,electrons,protons,etc) the individual impacts on the receptor will slowly form a diffraction pattern. Each particle impacts like a point impact, but are diffracted like a wave, and will in total form a diffraction pattern just like they were all part of a single wave of energy hitting the slits all at once even though each particle can be separated from others by hours and even come from completely different sources.

    From that and a thousand other types of experiments, the best explanation we’ve found (and the only one that has successfully predicted results yet untested) is that each particle of matter – leptons,bosons,quarks, and the things they make up like protons, neutrons, and the things that protons and neutron come together to build like helium,lithium, etc – all of that – behave just like they are waves until specifically interacted with at which point the interaction collapses the wave function down to a specific point.

    The wave which makes up different particles is spread across space, not in one single location until it interacts with something that collapses it down to a point location, such as the receptor on the other side of the slits.

    Those waves aren’t evenly spread across space though, they are concentrated with a high probability around a particular area, but their wave probability drastically diminishes as it moves further away from that area.

    However, that does bring about some cool effects. Let’s use electrons for examples. Let’s say you have electrons zipping around the processor of your computer right now. The paths in your processor are so small that they start getting down to the scale at which an electron actually has a significant chance at not existing inside your computer processor’s path. It can (and does fairly often) no longer exist inside the processor’s path and suddenly it exists outside in the material around the path – giving the material there a sudden ZAP as the wave function which was only MOSTLY centered in the processor’s path suddenly exists outside the path where the electron’s probability of existing was low, but definitely not zero.

    Computer chip manufacturers have to take that into account, and it is one of the limiting factors on how small processors can get. As the processors get smaller and smaller paths and switches, the electrons which it is passing along have a higher and higher probability of existing outside the path.

    Twenty years ago the paths were large enough that an electron only had a 1 in 10^15 or greater chance of suddenly existing outside the path: 1 in a quadrillion electrons would suddenly jump, causing an error which they had to handle. Twenty years ago the processors were only handling a few billion electrons per second, and thus the errors only happened once ever couple million seconds. No biggie, and relatively easily handled.

    With more modern processors, the chances of an electron’s wave suddenly existing outside the path are more in the 1 in a billion order of magnitude. Considering that processors today are handling hundreds of billions of electrons per second, it’s a MUCH bigger problem.

    There are ways to handle it and minimize the risk and things, but the sudden “teleportation” if you will, is a relatively frequent occurrence. While you’ve been working on your computer, there may have been thousands of electrons which suddenly stopped existing in your computer processor’s paths and suddenly existed outside.

    Engineers have also used this effect to to their advantage in some situations – “teleporting” particles across barriers without impacting the barriers.

    Way cool stuff!

  • WebMonk

    Like nqb said, it’ll drive you nuts if you try to think of how it can be in two places at once. The double-slit phenomena is real, as are a multitude of other effects. I’m not 100% sure we know truly what is going on, but we have figured out an EXTREMELY good way of understanding it, so maybe that understanding is really what is going on.

    Basically, light (and everything) exists as a probability wave – every proton in your body doesn’t exist as a solid thing, it exists as a probability of being in the carbon atom making up one of your DNA sequences. The probability of it being there is very high, but not 100%. It exists at a variety of different locations, but the probability of it being located in that carbon atom is huge while the probability of it existing a couple cm away is minuscule (but not zero).

    Piece of background: if you see a water wave going through two slits, it will go through them both and diffract through them, making a light and dark pattern on the other side as the wave has been split into two and interact with each other.

    That’s an effect we can see with the double-slit experiment – an experimenter sends a single photon of light or a single electron at material with two tiny slits in it. The single photon hits a receptor on the other side as a single photon, diffracted off in some direction.

    Send in another photon an hour later, and you can see it’s impact on the receptor, diffracted off in a different direction. Solid particles moving through slits aren’t diffracted, only waves are diffracted. However, when the electron or photon is sensed on the other side, it has been diffracted (a wave) but makes a single dot on the receptor (particle).

    Not only that, but if you feed lots and lots of single particles (photons,electrons,protons,etc) the individual impacts on the receptor will slowly form a diffraction pattern. Each particle impacts like a point impact, but are diffracted like a wave, and will in total form a diffraction pattern just like they were all part of a single wave of energy hitting the slits all at once even though each particle can be separated from others by hours and even come from completely different sources.

    From that and a thousand other types of experiments, the best explanation we’ve found (and the only one that has successfully predicted results yet untested) is that each particle of matter – leptons,bosons,quarks, and the things they make up like protons, neutrons, and the things that protons and neutron come together to build like helium,lithium, etc – all of that – behave just like they are waves until specifically interacted with at which point the interaction collapses the wave function down to a specific point.

    The wave which makes up different particles is spread across space, not in one single location until it interacts with something that collapses it down to a point location, such as the receptor on the other side of the slits.

    Those waves aren’t evenly spread across space though, they are concentrated with a high probability around a particular area, but their wave probability drastically diminishes as it moves further away from that area.

    However, that does bring about some cool effects. Let’s use electrons for examples. Let’s say you have electrons zipping around the processor of your computer right now. The paths in your processor are so small that they start getting down to the scale at which an electron actually has a significant chance at not existing inside your computer processor’s path. It can (and does fairly often) no longer exist inside the processor’s path and suddenly it exists outside in the material around the path – giving the material there a sudden ZAP as the wave function which was only MOSTLY centered in the processor’s path suddenly exists outside the path where the electron’s probability of existing was low, but definitely not zero.

    Computer chip manufacturers have to take that into account, and it is one of the limiting factors on how small processors can get. As the processors get smaller and smaller paths and switches, the electrons which it is passing along have a higher and higher probability of existing outside the path.

    Twenty years ago the paths were large enough that an electron only had a 1 in 10^15 or greater chance of suddenly existing outside the path: 1 in a quadrillion electrons would suddenly jump, causing an error which they had to handle. Twenty years ago the processors were only handling a few billion electrons per second, and thus the errors only happened once ever couple million seconds. No biggie, and relatively easily handled.

    With more modern processors, the chances of an electron’s wave suddenly existing outside the path are more in the 1 in a billion order of magnitude. Considering that processors today are handling hundreds of billions of electrons per second, it’s a MUCH bigger problem.

    There are ways to handle it and minimize the risk and things, but the sudden “teleportation” if you will, is a relatively frequent occurrence. While you’ve been working on your computer, there may have been thousands of electrons which suddenly stopped existing in your computer processor’s paths and suddenly existed outside.

    Engineers have also used this effect to to their advantage in some situations – “teleporting” particles across barriers without impacting the barriers.

    Way cool stuff!

  • Bryan Lindemood

    Thanks everyone, I was aware of the double slit experiment – but I enjoy reading about people’s explanations and the questions this raises. I look forward to digesting a bit of this stuff. I am very curious as to the WHY.

    Do subatomic mechanix rest on paradoxical truth? That would be too funny.

  • Bryan Lindemood

    Thanks everyone, I was aware of the double slit experiment – but I enjoy reading about people’s explanations and the questions this raises. I look forward to digesting a bit of this stuff. I am very curious as to the WHY.

    Do subatomic mechanix rest on paradoxical truth? That would be too funny.

  • nqb

    bunnycatch3r, what exactly do you mean when you say “varying results?” I am going to anticipate two things you may mean, but maybe I’m missing your question:
    First, the double slit will always give the same results under the same conditions. The cases of the diffraction appearing and disappearing are really different “experiments.” For example, dropping a ball on earth and on the space shuttle in orbit could both be called the “ball drop experiment,” but you would get very different results without contradiction.
    Second, you could be referring to the random collapse of systems to different values. So the first time I measure a quantum particle I get value “A” and the second time (after I’ve prepared the particle again) I get value “B” even though this time the experiment was exactly the same. Well, this really is a mystery of quantum mechanics, but it doesn’t mean there isn’t truth. I can say at every point in time, “The particle is truthfully in [whatever state it is in].” An analogous scenario is the spinner in the game Twister. Even though I get a different color each time I spin it, I understand that there isn’t a contradiction. I can say, “The spinner is on blue” or “The spinner is spinning” at all times with complete confidence, though I can’t predict what it will be later. Similarly I can say, “The particle is of value ‘A’” or “The particle is in a superposition of value ‘A’ and ‘B.’”

  • nqb

    bunnycatch3r, what exactly do you mean when you say “varying results?” I am going to anticipate two things you may mean, but maybe I’m missing your question:
    First, the double slit will always give the same results under the same conditions. The cases of the diffraction appearing and disappearing are really different “experiments.” For example, dropping a ball on earth and on the space shuttle in orbit could both be called the “ball drop experiment,” but you would get very different results without contradiction.
    Second, you could be referring to the random collapse of systems to different values. So the first time I measure a quantum particle I get value “A” and the second time (after I’ve prepared the particle again) I get value “B” even though this time the experiment was exactly the same. Well, this really is a mystery of quantum mechanics, but it doesn’t mean there isn’t truth. I can say at every point in time, “The particle is truthfully in [whatever state it is in].” An analogous scenario is the spinner in the game Twister. Even though I get a different color each time I spin it, I understand that there isn’t a contradiction. I can say, “The spinner is on blue” or “The spinner is spinning” at all times with complete confidence, though I can’t predict what it will be later. Similarly I can say, “The particle is of value ‘A’” or “The particle is in a superposition of value ‘A’ and ‘B.’”

  • http://www.geneveith.com Gene Veith

    Thanks, Webmonk, for that fascinating explanation! Bunnycatch3r, I would say that just because something is unlogical that doesn’t mean it is subjective! Quantum physics staggers our limited intellects, though there is objective evidence for it, and though it can be expressed quite well mathematically. Other true things also stagger our limited intellects, including mysteries such as the Trinity. Our subject constructions, by contrast, would be much simpler than things that are true!

  • http://www.geneveith.com Gene Veith

    Thanks, Webmonk, for that fascinating explanation! Bunnycatch3r, I would say that just because something is unlogical that doesn’t mean it is subjective! Quantum physics staggers our limited intellects, though there is objective evidence for it, and though it can be expressed quite well mathematically. Other true things also stagger our limited intellects, including mysteries such as the Trinity. Our subject constructions, by contrast, would be much simpler than things that are true!

  • bunnycatch3r

    @nqb If I understand the http://www.youtube.com/watch?v=DfPeprQ7oGc correctly, a beam of electrons act like particles when observed but as waves when unobserved. It’s as if the electrons are “aware” they are being observed. The observer in this experiment varies the results (or collapses the wave function) merely by observing. This what I mean by varying results.
    Thank you Dr Veith for your response. I wonder though, in a post-quantum world, if the terms “objective” and “subjective” will still retain their respective connotations. Of the two, currently, the former is preferable when discussing matters of religion, science, and philosophy. But on the other side of the quantum looking glass we all may be arguing spiritedly that we have the more subjective world view.
    I also asked the question because I believe (I could be wrong) that to be one of the chief questions a post-modernist would ask of religion.

  • bunnycatch3r

    @nqb If I understand the http://www.youtube.com/watch?v=DfPeprQ7oGc correctly, a beam of electrons act like particles when observed but as waves when unobserved. It’s as if the electrons are “aware” they are being observed. The observer in this experiment varies the results (or collapses the wave function) merely by observing. This what I mean by varying results.
    Thank you Dr Veith for your response. I wonder though, in a post-quantum world, if the terms “objective” and “subjective” will still retain their respective connotations. Of the two, currently, the former is preferable when discussing matters of religion, science, and philosophy. But on the other side of the quantum looking glass we all may be arguing spiritedly that we have the more subjective world view.
    I also asked the question because I believe (I could be wrong) that to be one of the chief questions a post-modernist would ask of religion.

  • nqb

    bunnycatch3r, that’s a great video. And your understanding is correct: The observer in this experiment varies the results (or collapses the wave function) merely by observing. But then again, how do you merely observe an electron? People (even physicists) often use the word “merely” or “simply” when describing quantum observations, but observations on the quantum level are necessarily different than your everyday observation.
    This is exactly what I was getting at with my “different experiments” explanation. The analogous “ball drop” experiment here is doing it with the lights on and off. First, I drop a ball in the dark, then turn on the lights and see that it’s on the floor. Then, I keep the lights on and observe the ball as it falls to the floor. Same experiment, same result, right? Well, actually the experiments aren’t exactly the same because in the second case I have added a huge number of (insignificant) photon collisions with the ball. But the photon-ball collisions are only “insignificant” because of the relative sizes involved (i.e., the photons don’t alter the motion of the ball much at all). But for an electron-photon collision (or however you observe the electron), the observation changes the experiment much more dramatically.
    I’m not trying to demystify quantum mechanics because superpositions, entanglement, quantum teleportation, etc., it’s all real and it’s all bizarre. But quantum mechanics doesn’t really speak to everyday rationality or logic, though we often assume we just know what an “observation” or “particle” is.
    You’re right that a post-modernist may ask the question, and maybe now you have an answer.

  • nqb

    bunnycatch3r, that’s a great video. And your understanding is correct: The observer in this experiment varies the results (or collapses the wave function) merely by observing. But then again, how do you merely observe an electron? People (even physicists) often use the word “merely” or “simply” when describing quantum observations, but observations on the quantum level are necessarily different than your everyday observation.
    This is exactly what I was getting at with my “different experiments” explanation. The analogous “ball drop” experiment here is doing it with the lights on and off. First, I drop a ball in the dark, then turn on the lights and see that it’s on the floor. Then, I keep the lights on and observe the ball as it falls to the floor. Same experiment, same result, right? Well, actually the experiments aren’t exactly the same because in the second case I have added a huge number of (insignificant) photon collisions with the ball. But the photon-ball collisions are only “insignificant” because of the relative sizes involved (i.e., the photons don’t alter the motion of the ball much at all). But for an electron-photon collision (or however you observe the electron), the observation changes the experiment much more dramatically.
    I’m not trying to demystify quantum mechanics because superpositions, entanglement, quantum teleportation, etc., it’s all real and it’s all bizarre. But quantum mechanics doesn’t really speak to everyday rationality or logic, though we often assume we just know what an “observation” or “particle” is.
    You’re right that a post-modernist may ask the question, and maybe now you have an answer.

  • bunnycatch3r

    @nqb I’ve read through your response a few times and I find your insight quite interesting. And yes, the word “merely” was something I think I picked up from the video and decided to include because it mystifies an already fantastic subject. I agree, quantum reality is different than our everyday rationality but I surmise that we live in a culture who’s values mirror it -especially in regards to concepts like Truth and objectivity. Thanks again for responding to my questions.

  • bunnycatch3r

    @nqb I’ve read through your response a few times and I find your insight quite interesting. And yes, the word “merely” was something I think I picked up from the video and decided to include because it mystifies an already fantastic subject. I agree, quantum reality is different than our everyday rationality but I surmise that we live in a culture who’s values mirror it -especially in regards to concepts like Truth and objectivity. Thanks again for responding to my questions.

  • http://www.simdan.com SimDan

    @bunnycatch3r
    “I also asked the question because I believe (I could be wrong) that to be one of the chief questions a post-modernist would ask of religion.”

    Indeed, the very video of Dr. Quantom comes from a film titled “What the Bleep Do We Know!?” This film seems to push some form of new-age spirituality.

  • http://www.simdan.com SimDan

    @bunnycatch3r
    “I also asked the question because I believe (I could be wrong) that to be one of the chief questions a post-modernist would ask of religion.”

    Indeed, the very video of Dr. Quantom comes from a film titled “What the Bleep Do We Know!?” This film seems to push some form of new-age spirituality.

  • Rich Cork

    I think everyone is overlooking the most weird thing on the horizon which relates directly to this. They way I understand it, chip speed is one of the only things holding back those working on construction of artificial brains. Blade Runner??????? What a host of ethical, theological……questions that brings up.

  • Rich Cork

    I think everyone is overlooking the most weird thing on the horizon which relates directly to this. They way I understand it, chip speed is one of the only things holding back those working on construction of artificial brains. Blade Runner??????? What a host of ethical, theological……questions that brings up.

  • WebMonk

    And talking of quantum weirdness and observations, it doesn’t seem to be “just” the observation which changes things. It’s not just a function of the act of observing which limits our precise knowledge of quantum particles – it is that the quantum particles truly are not precise – there really isn’t a determined momentum-location to a particle.

    In other words, it’s not just because an observation disturbs the particle that we can’t know a particle’s momentum and location at the same time — it’s because the particle really doesn’t have a set momentum and location.

    There are quite a number of experiments that show this, and if I weren’t about to head out the door, and if I hadn’t already written a massive post earlier here, I’d describe one of them.

    Anyone interested, though, and always head over to Wikipedia!

  • WebMonk

    And talking of quantum weirdness and observations, it doesn’t seem to be “just” the observation which changes things. It’s not just a function of the act of observing which limits our precise knowledge of quantum particles – it is that the quantum particles truly are not precise – there really isn’t a determined momentum-location to a particle.

    In other words, it’s not just because an observation disturbs the particle that we can’t know a particle’s momentum and location at the same time — it’s because the particle really doesn’t have a set momentum and location.

    There are quite a number of experiments that show this, and if I weren’t about to head out the door, and if I hadn’t already written a massive post earlier here, I’d describe one of them.

    Anyone interested, though, and always head over to Wikipedia!

  • WebMonk
  • WebMonk
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