First Demonstration Of Time Cloaking

Also, our basic understanding of physics-as-applied-to-the-limits-of-technology hasn't much changed from 1960 to 2010, unlike the period from 1910 to 1960.

But the coming technology and culture they're describing is either difficult to show compellingly onscreen, requires an outlier in IQ and education to understand, or is somewhere between disturbing and revolting to people who have no problem with starships and phasers.

[1]http://news.ycombinator.com/user?id=cstross

Maybe I have a weak imagination, but Star Trek and other sci-fi have probably done anything that can be done with any kind of technology we can come up with. Beyond sci-fi is fantasy land, and sci-fi as a genre has reached that border, beyond that its where Harry Potter and Lord of the Rings take over.

Check out Halting State by Charles Stross and Rainbows End by Vernor Vinge.

Frank Herbert was the one right. His extrapolation of 20th century is a dystopia and utopia at the same time.

But even he couldn't foresee that we will create no-chamber at the start of 21st century.

Then the whole world seemed to sink back into skepticism and the regular blasé mood.

This is as odd as the rampant insanity that took over the world two decades prior to that.

The 20th century was very very strange.

Now that I've answered that, let's caution you about your deployment of Mr. Cat. First of all, I don't believe you'll need an uncertain quantum object to observe in this particular thought experiment. Life is complicated enough without bringing in more quantum mechanics than you need. Just imagine a brick. It's red. Light is shining on the brick and it looks red. Now, I install my time-bending lenses around the brick, and then at one particular instant the brick changes to be yellow, and then goes back to being red. But you don't see that, you just see a continuously red brick, even though the light was "shining on" the brick the whole time, because our lenses made a "time hole" in the stream of light and the color change happened during the hole.

I should also warn you that our friend Mr. Cat is a bad metaphor in many ways. (He was originally an in-joke, after all, used by people who were debating the apparent absurdity of a new theory.) The problem with the cat is that he's a completely unrealistic creature, and he primes your intuition in all sorts of incorrect ways. In real life you will never stumble across a coherent superposition of two quantum states as dramatically large (trillions of cells!) and dramatically different (alive vs dead!) as this imaginary cat. Real cats interact with their surroundings. A lot. They breathe and meow, they emit organic molecules that smell like cat, they charge up with static electricity (electric fields) and then run around in circles (magnetic fields), and above all they gravitate (which is difficult to cloak). So to make the thought experiment work the cat's imaginary box has to be a cloaking device, a box that permits no interaction with the outside world until it is "opened". And that doesn't exist in real life.

And, therefore, importing the cat into this thought experiment is a particularly bad move, because it's redundant. If you have Shroedinger's imaginary box you don't need an additional set of imaginary time-cloaking lenses. The box is already cloaking the cat, for a fairly long period of time.

Always be careful: Thinking about completely impossible things is fun for a while, but don't make a habit of it, or you'll become the sort of insufferable spaced-out quantum-mechanics groupie who says things like gosh, maybe when I turn around and stop believing in this tree it will cease to exist. Of course not. Tree-sized objects do not physically disappear from your universe, not without the sound of a chainsaw.

Instead of a cat, consider a situation where you could 'use' this time lens, if it operated over human-scale time periods. I sneak the time lens into your party, disguising it as a beer keg. At an appropriate moment, I trigger it; then I rush over to your wall safe, open it and extract the diamonds stored within, close the safe, and return to my starting position. From your point of view, everything is as it was before. Unless you were looking at the clock - in which case you would see it jump forward by two minutes! You realize someone at the party has been using a time lens, and raise the alarm. Suspicion soon falls upon me, and I shamefacedly produce the diamonds from my pocket.

But just as you and your friends are about to lay hands on me, I vanish! I triggered the time lens again, and slipped out between you, unobserved.

Of course, I can't see what's going on with the time lens either, in all likelihood; perhaps I need some sort of ninja skills to move blindly through the temporal hiatus.

No, that is wrong. The cat does not live or die. The cat is both alive and dead at the same time. This is why so many people have problems understanding quantum mechanics -- they don't seem to get the implications of a state being a probability. Schrödinger came up with his cat in an attempt to make the reality clear to other people, and yet many intelligent people misinterpret what Schrödinger's point was. It's important to get this right: the cat is both alive and dead. Both. If the scenario wasn't so extremely counter-intuitive, then there would not have been a need to invent it in the first place.

As for what exactly constitute a temporal probe, I am not certain. Some form of laser meant to be manipulated by the occurrence of an event perhaps.

probable application: Magicians can make their tricks completely undetectable using a cloak while they do them (assuming they can do them in sub-microsecond time).

We all learn about causality. Things don't just happen without being there being some kind of reversible action. If an ice cube melts, that's a time reversible aspect of physics. Basically if you could run time backwards like a video in reverse, you would see the ice unmelt.

In another instance, imagine a block of ice in the middle of a star. There's no way that a chunk of ice can just appear in a star. Now, that's not to say its impossible for such a chunk to be there. But you can trace back a line of actions that led to it being there, ranging from the debris of the spacecraft that contained it to the launch pad on a planet orbiting nearby, to all of the patterns of matter and information encompassing the civilization that built and launched it in the first place.

So if I'm understanding this correctly, the temporal cloak effectively allows stuff to happen inside it that isn't detectable from the outside. To stretch my last analogy a bit, imagine you put such a temporal cloak around the entire civilization leading up to where the ice ends up in the star. To an outside observer, say some aliens doing a research study on our star, all of a sudden they would detect the block of ice in the star but not have any idea where it came from.

here's the relevant bit:

Alternatively, it may be desirable to cloak the occurrence of an event over a finite time period, and the idea of temporal cloaking was proposed in which the dispersion of the material is manipulated in time to produce a "time hole" in the probe beam to hide the occurrence of the event from the observer. This approach is based on accelerating and slowing down the front and rear parts, respectively, of the probe beam to create a well controlled temporal gap in which the event occurs so the probe beam is not modified in any way by the event.

Time-space duality represents the analogy between diffraction and dispersion that arises from the mathematical equivalence between the equations describing the diffraction of a beam of light and the one-dimensional temporal propagation of a pulse through a dispersive medium [17,18]. Similar to a spatial lens that imparts a quadratic phase in space, a time-lens can be implemented that produces a quadratic phase shift in time [19{21]. This time-lens can, for example, magnify [22] or compress [23] signals in time and has an equivalent of the lens law. Time-lenses can be created with an electro-optic modulator [18] or via a parametric nonlinear optical process such as four-wave mixing (FWM) with a chirped pump wave [19,20]. In the latter case the signal wave is converted to an idler wave with a linear frequency shift in time (i.e., a quadratic phase in time) [21,22].

I understand this to mean that the passage of time in observed space can be slowed down relative to an observer, rather as happens when observing a body falling into a black hole.