David Kirkpatrick

June 11, 2008

Quantum cryptography

Move over one-time pad, there’s a new kid on the cryptographic block — quantum cryptography. This is one amazing application for the weirdness that is quantum mechanics and quantum effects. And one cool way to transmit secret messages.

Today’s KurzweilAI.net newsletter had a link to a Scientific American story on space-based quantum codes used for cryptography.

Over at Bad Astronomy, Phil Plait wrote about this on Monday. He offers a cool short-version explanation of the quantum mechanics involved, and his comment section has even more detail provided by BABlog readers.

Here’s the KurzweilAI  short:

Space Station Could Beam Secret Quantum Codes by 2014
ScientificAmerican.com, June 9, 2008

University of Vienna researchers hope to send an experiment to the International SpaceStation (ISS) by the middle of the next decade that would pave the way for transcontinental transmission of secret messages encoded using quantum entanglement.

(European Space Agency

In addition to potential use for secure communications, the “Space-QUEST” project would give researchers a chance to test the theory that entanglement should be unlimited in range.

Read Original Article>>


Here’s an excerpt from the Scientific American link found above at “Read Original Article”:

Researchers hope to send an experiment to the International Space Station (ISS) by the middle of the next decade that would pave the way for transcontinental transmission of secret messages encoded using the mysterious quantum property of entanglement.

When two particles such as photons are born from the same event, they emerge entangled, meaning they can communicate instantaneously no matter how far apart they are. Transmitting entangled pairs of photons reliably is the backbone of so-called quantum key distribution—procedures for converting those pairs into potentially unbreakable codes. Quantum cryptography, as it is known, could appeal to banks, covert government agencies and the military, and was tested in a 2007 Swiss election

Here’s some of Phil Plait’s commentary at Bad Astronomy:

So some European scientists came up with the idea of using the International Space Station (I know! Using ISS for science! Wow!) to test this out. They can create a small setup with a laser which can create entangled photons. The entangled photons are then sent simultaneously to two different ground stations, widely separated on the surface of the Earth, so that both have a copy of the entangled photons. In addition, two quantum keys are created based on the photons; this is essentially a code based on the state of the photons — like winning a bet is based on which way a coin lands. The two keys are different, and one each is sent to the two ground stations. So both stations have a pair of entangled photons (identical to the other station’s) and a different key.

Each key is actually a long chain of 1s and 0s. The two keys are then compared on the ISS to create what’s called a bitwise XOR — for example, if two coins both land heads then the XOR operation yields a 0, but if they land differently (one heads and one tails) then it yields a 1 — it’s just telling you whether they are the same or different. So for each place in the key, the two numbers are compared, and if they’re the same (both 1s or both 0s) then a 0 is written down. If they are different then a 1 is put there. When this is done, you get a third string of 1s and 0s, representing a comparison of the two keys.

Still with me? Yeah, me neither, but we’re almost done. So now the ISS has this long number string which represents whether the keys are alike or different. It then transmits this to one of the two stations on Earth.

So? What does this mean? This means that now the two ground stations can create a code between them based on their keys, a code that is known only to them and no one else. Furthermore, this code cannot be cracked by anyone, anywhere, because it’s based on entangled photons that cannot be known to anyone else! Because of entanglement, they know what the other station has because they can look at their key and figure it out. But no one else can.

April 16, 2008

“Expelled” antidote

Filed under: Arts, et.al., Media, Science — Tags: , , , — David Kirkpatrick @ 12:49 am

Phil Plait over at Bad Astronomy has some antidote for the new film by proponents of “intelligent design” — Expelled: No Intelligence Allowed. (Oh whither hast thou gone, Ben Stein?)

From the link:

What? Someone makes a movie arguing against evolution and it turns out they’re a bunch of evil lying frauds? How can such a thing be?


It’s true: the makers of the movie Expelled: No Intelligence Allowed have been lying their heads off since square one. I would go into details, but I don’t need to: The National Center for Science Education (Genie Scott’s group) has created a wonderful website which explains very carefully just how evil the Expelled crowd is. The site is called Expelled Exposed, and I highly recommend sending everyone you know there, especially if they may be prone to listen to a propaganda piece like the movie. They more than anybody need to know the truth behind it.

March 20, 2008

Joyride in space, anyone?

Filed under: Arts, et.al., Media, Science, Technology — Tags: , , , , , — David Kirkpatrick @ 6:29 am

Looks like the doors are open and the keys are in the ignition. Let’s go for a a spin …
(link above goes to the full-sized image)


(Hat tip — Bad Astronomy)

GIF loop of lunar impact

Filed under: Science — Tags: , , , , — David Kirkpatrick @ 3:44 am

This is one cool post from Bad Astronomy. A recorded, and confirmed, meteor impact on the moon.

From the link:

Image from George Varros of a meteor impact on the MoonAmateur astronomer George Varros did just that on March 13, and better yet, he had a video camera hooked up to his telescope! He captured an impact, and has an animation on his site of it; the image above is a still from it.These are notoriously hard to get on video, and even then they are harder to confirm; it might be something else like a flaw in the camera. But in this case, other cameras caught it, so this has been confirmed; it was the equivalent of about 100 kilograms of TNT exploding on the lunar surface. Assuming an impact speed of 30 km/sec (that’s a complete guess, but about the speed of an orbiting object near the Earth’s distance from the Sun) the object itself would have massed about a ton kilogram. If it were a rocky sphere it would have been about a meter across 10 centimeters across, roughly the size of a baseball. Not something you want hitting your house!

Varros has a page listing other impacts he’s caught as well. Very cool, and very useful! Eventually, when we go back to the Moon, the number and size of impacts on the surface will determine how we build structures on — or below — the lunar surface.

February 15, 2008

Major astronomy discovery — a twin for Jupiter

Filed under: Science — Tags: , , , — David Kirkpatrick @ 10:19 pm

This is very cool. We’ve found a gas giant planet the same size as Jupiter, and orbiting a similar sized star to our sun at roughly the same distance, a mere 60 light years away.

From Phil Plait’s Bad Astronomy explaining just how important this discovery really is:

Finding a planet like this isn’t as easy as it sounds! Finding planets with the same mass as Jupiter isn’t hard; many have been found with even lower mass. The hard part is finding one that is orbiting a sun-like star at the same distance Jupiter orbits our Sun. The closer in a planet is to its star, the easier it is to find: the method used measures how hard the planet’s gravity tugs on its parent star as it orbits; the planet pulls the star around just like the star pulls the planet, and we see this as a change in the velocity of the star toward and away from us (called the radial velocity; Wikipedia has a nice animated GIF for this), and that effect gets bigger with bigger planets, and the closer they orbit.

January 29, 2008

Spysat reentry

Filed under: Science — Tags: , , , , — David Kirkpatrick @ 12:55 pm

Yowza. A US spy satellite is coming home the hard way in February or March. What makes this event exciting (not the good type of exciting) is we’ve lost control over the craft so it can’t be guided safely into the ocean.

The real trick is satellites don’t completely disintegrate on reentry, they dump some amount of debris on Earth’s surface. And they tend to leave a trail of various chemicals through all the layers of the atmosphere.

All this means is this is an event to at least keep up with because there is some measure of danger, however very, very tiny that danger might be. Odds are high any debris will hit one of the oceans anyway.

Very unlike the overhyped TU24 asteroid event which poses absolutely no threat to our beautiful planet.

(Find an update to the spysat story here.)