Photonic matter: are real lightsabers on the horizon?

Raising the concealed carry weapon issue to a whole new level.

For your Just Too Cool file from

New form of photon-based matter is essentially a lightsaber

Modern physics has taught us quite a lot about light and how it behaves, but some of what we thought we knew might not be entirely accurate. A team of scientists from MIT and Harvard have been herding photons through a cloud of super-cold atoms in an attempt to get them to do something that was once considered impossible — bind together. According to a new paper, they may have succeeded in creating a new form of matter entirely from photons, which is basically a lightsaber.
Conventional wisdom holds that photons are massless particles that don’t interact with each other, so how can they form molecules? [I’d like to know!] The key was to create a special medium in which photons can interact strongly enough that they attract one another as if they have mass. This so-called “photonic matter” has been theorized for some time in scientific circles, but only in the abstract.

The team used a vacuum chamber filled with rubidium atoms to facilitate the formation of photonic matter. The cloud of gas was cooled to within a few degrees of absolute zero using (fittingly) lasers. Short laser pulses were then used to send individual photons into the cloud where the chilled gas sapped energy away from them, causing the photons to slow down considerably by the time they exited the cloud. If more than one photon was sent in at the same time, the researchers found the particles would lose so much energy that they emerged together as a single molecule.

The Harvard and MIT scientists believe this newly observed interaction between photons could be of great importance in the field of quantum computing. Photons have been studied as a medium for doing quantum calculations, but one of the principal challenges has always been that they don’t interact with each other. Well, now there might be a way to make that happen in the context of a quantum computer. The process still needs to be refined, but it’s an exciting proof-of-concept.
A few photons sticking together is a long way from a lightsaber, but we can still dream, can’t we?  [Yes!]

About Fr. John Zuhlsdorf

Fr. Z is the guy who runs this blog. o{]:¬)
This entry was posted in Just Too Cool and tagged , , , , . Bookmark the permalink.


  1. Legisperitus says:

    For those who live in the southern US, any excitement over this development is tempered by the realization that shortly after the invention of lightsabers will follow the phenomenon of rednecks with lightsabers….

  2. Darren says:

    Legisperitus; sounds like a potential new reality series! “ah’s yer Pappy Luke!”

    “Ca’ful aroun’ th’ still wit thet light sabre!”

  3. wmeyer says:

    Legisperitus, for that generalization, it seems appropriate to refer you to Fr. Z’s “prayer before connecting to the internet.” Charity, please.

  4. inexcels says:

    As someone who does research in a related field, let me say that quantum computers could certainly use a boost. All the existing designs are worthless.

    But light sabers would be a far more viscerally awesome use for this technology.

  5. pledbet424 says:

    Yoda, Obi-Wan, Luke = Rednecks
    Evil Emperor, Darth Vader, Storm Troopers = Obama and the NSA

  6. off2 says:

    As a wannabe red neck (impossible as mother was a lady from Philadelphia), who studied physics 50 years ago, I ask, with some seriousness, have they changed the definition of a molecule, an item composed of atoms?

  7. Darren says:

    off2: A molecule remains the smallest particle of a material/substance that retains its properties, usually consisting of two or more atoms. When I was in grammar school atoms were then made up of protons, neutrons and electrons. Since then all of these even smaller particles have been discovered and/or theorized… quarks, neutrinos, photons etc. Maybe they aren’t all so new, but when I was in grammar school (70’s into the 80’s), they never talked about them.

    To this day, however, I have not heard anything official about midichlorians!

  8. Fr. Z – I had a ‘vision’ of you accidently activating your lightsabre during Holy Mass and slicing off the server’s arm!

    It would be cool to have lightsabres but I think cold steel is cooler. In truth, if they ever get this to work quantum computers would be just a start. Imagine superfast AIs with energy weapons! Laser carrying Robo-armies! Armageddon! :)

  9. The Masked Chicken says:

    Hello, quantum theorist, here.

    This news article is analogous to the hatchet job done on Pope Francis’s interview. Thanks a lot. I spent all morning trying to figure out what would happen if you passed a photon through a rubidium crystal and the best I could come up with is that it would induce a phase shift. It turns out that that is exactly what happens. Two, and only two photons at a time, have their phases twisted towards each other, which is, technically, a form of attraction in phase space. If the wavefunctions of the two photons were, say, 100 degrees out of phase, then passing them through the rubidium crystal causes the bound state photon pair to have a phase difference of only, say, 80 degrees, so the phases have been, “attracted”. Technically, they have been made more coherent, which is exactly what the abstract in Nature says. I think this has been known to happen in non-linear crystal interactions for years, but, I suspect this has only been measured with electron, before (I’d have to do a literature review and this phenomenon doesn’t interest me enough to take the time).

    There are no molecules involved, here. The reporter is fantasizing, which is the polite way to say he has no idea of what he is talking about.

    From Nature’s abstract, with my comments:

    “The fundamental properties of light derive from its constituent particles—massless quanta (photons) that do not interact with one another [note: do not interact]1. However, it has long been known that the realization of coherent interactions [there’s the key word – coherent] between individual photons, akin to those associated with conventional massive particles, could enable a wide variety of novel scientific and engineering applications2, 3. Here we demonstrate a quantum nonlinear medium inside which individual photons travel as massive particles with strong mutual attraction, such that the propagation of photon pairs is dominated by a two-photon bound state4, 5, 6, 7. We achieve this through dispersive coupling of light [source of the photons; dispersion => non-linear, in this case. There is such a thing as linear dispersion] to strongly interacting atoms in highly excited Rydberg states [Rydberg states are states close to the quantum-classical limit in size. The atoms are in Rydberg states, which can have non-linear properties. In this case, the electron wavefunctions can interact with the photon wavefunctions, by a process I don’t know about, although I suspect that the highly excited Rydberg states have upper energy levels where the energy density is so low that that region of the electron behaves, functionally, like a photon so that the electron-photon interaction causes a phase drag on the photon. I’d have to read the article to be sure, but it’s behind a paywall. ]. We measure the dynamical evolution of the two-photon wavefunction using time-resolved quantum state tomography, and demonstrate a conditional phase shift8 exceeding one radian, resulting in polarization-entangled photon pairs [there it it]. Particular applications of this technique include all-optical switching [i.e., high phase separation = off, low phase separation = on], deterministic photonic quantum logic [high phase = 1, low phase = 0] and the generation of strongly correlated states of light9.

    Nothing to see here about light sabers. Now, it will be discovered in 2051 that it is possible to magnetically trap the electromagnetic vectors of photons and arrange them in a linear column, but you didn’t here that from me. I’m supposed to be doing this time travel thing under cover.

    The Chicken

  10. The Masked Chicken says:

    Sorry, for the spelling errors. We have computers that type what we say, so no one learns to spell where I’m from :(

    The Chicken

  11. inexcels says:

    Thanks, Chicken. Shocking that a journalist would misreport a scientific discovery, isn’t it?

    To be fair on the poor journalists, all the low-hanging fruit was discovered a long time ago so now one needs advanced degrees just get an inkling what it is that’s been discovered.

  12. Marion Ancilla Mariae says:

    Masked Chicken,

    May I ask you a question? (I don’t know physics at all, only have read bits of it here and there.) I was waiting for someone to bring up the property of light which responds to gravity. Was it Einstein who noted that beams of life appear to “bend” toward planets? And who hypothesized that photons do, indeed, possess some infinitesimally small mass, enough so that the mass of a large body such as a planet does exert some pull on them. Isn’t that why black holes are black? The light can’t escape at all because of the tremendous gravitational pull of the collapsed star.

    Anyway I am way at the outer reaches of anything I know or understand. But all this is very interesting. Thanks.

  13. Random Friar says:

    It’s 2013. We were promised flying cars. Where are the flying cars? Let’s work on that first.

  14. Marion Ancilla Mariae says:

    Flying cars. Heh.

    If I ever invested in a start-up that was in any way involved in bringing flying cars to market, I would first quit my job, put all my assets in the names of relatives, get a phoney ID and SSN, and get a different job . . . because if you were to stack the court documents from all the lawsuits that would ensue from all the people who would be injured and killed, and all the homes, businesses, and roadways destroyed by flying car accidents, they would paper over the orbit of Uranus five times.

    And that would be just in the first year.

  15. The Cobbler says:

    I was just going to ask if it’s really a vacuum chamber if it’s full of rubidium.

    I’m not really qualified to say anything about quantum physics because unlike the vast majority of the people who talk about it I know what I don’t know. Genuine quantum physics as expounded by the likes of the Chicken seems, in my limited experience, to be an attempt to use theoretical mathematics to explain subatomic phenomena precisely without giving atoms the ability to truly violate normal physics (let alone things like philosophical causality, which physics couldn’t violate if it wanted to, if you know what I mean), but that might be some kind of oversimplification or misimpression (for instance, I couldn’t actually define “theoretical mathematics” for you — sorry; but at least I realize it, right?).

    I want a flying bike instead of a flying car, by the way. And lawsuits should be handled the same way they are for regular cars, shouldn’t they?

  16. Legisperitus says:

    wmeyer: I apologize if I appeared to generalize. Probably I should have mentioned that I was born, and still live, in the southern US and thus naturally don’t consider everyone who lives there a redneck.

Comments are closed.