Slashdot Mirror
New Idea Could Lead to Quantum RAM
KentuckyFC writes to tell us that scientists in Italy and the US have designed a new method of retrieving information from quantum memory that could allow them to create "Quantum RAM". "Giovannetti's idea is to send the address down the branching tree of connections in such a way that it only affects one switch at a time. The first address qubit sets a switch at the first branching point to go one way or the other; the second qubit is sent that way and sets the switch at the next branching point, and so on. The total number of entangled quantum systems is smaller, and they are not so susceptible to interference, allowing information to be retrieved from memory intact."
atomic-scale memory would create huge waves.
It also could help out on the heat issues as well.
I mean, think about how many atoms are in a normal piece of memory.... yeouch that's a lot of RAM!
Karma Whoring for Fun and Profit.
could this be used to implement extremely efficient binary trees? the structure sounds ideal to be but im hardly an expert.
[Guy 1] Hey, I had porn loaded into memory
[Guy 2] You changed it by looking at it!
How else will be I be able to add it to my gaming rig. Do you think this memory has lights on it? I hope so, and that'd look great through my case's side-windows.
Nothing in this really sounds like a new idea except that using this method would have some benefit on the quantum level. It's just a balanced binary decision tree implemented as a (quantum, in this case) circuit such that leaf nodes are stored data and addresses are qbit streams. Am I missing something?
Does that mean my data can travel back and forth through time, but only within my own lifetime?
Insert Generic Sig Here:
...3D Realms has announced that Duke Nukem Forever will require installation of quantum RAM.
Proud member of the Weirdo-American community.
Quantum computers are a real possibility. They just cease to exist if you try to observe them.
It is by the juice of the coffee bean that thoughts acquire speed, the teeth acquire stains. The stains become a warning
What? Yes, they exist, so far not with much memory though. One was used in '04 to implement Shor's Algorithm to factor the integer 15 (or 2^4-1). I know, baby steps, but sometimes I forget the factors of 15 :-/
Apology to Ubuntu forum.
A quantum register can be in a superposition of multiple states. For every possible state, there is a corresponding number called a probability amplitude. The square of the absolute value of the probability amplitude is equal to the probability that when observed, that state is the one you see, so naturally, the squares of the absolute values have to add up to 1. A quantum gate maps a single state onto a superposition of states.
:-)
Maybe an example will make this clearer. A quantum state is often written as a ket: |0> and |1>, for example. The Hadamard gate maps states like this:
|0> to (|0> + |1>)/sqrt(2)
|1> to (|0> - |1>)/sqrt(2)
If you feed |0> to a Hadamard gate, then the result will be a superposition of 0 and 1. 0's probability amplitude will be 1/sqrt(2), as will 1's. Feeding |1> into it will give you the same thing, except now 1's probability amplitude is -1/sqrt(2). (A probability amplitude can be a complex number.)
So suppose, now, that we feed (-|0> + |1>)/sqrt(2) (that is, 0 with amplitude -1/sqrt(2) and 1 with amplitude 1/sqrt(2)) into the Hadamard gate. You can just substitute the result in for the kets, like this:
(-|0> + |1>)/sqrt(2)
(-(|0> + |1>)/sqrt(2) + (|0> - |1>)/sqrt(2))/sqrt(2)
(-(|0> + |1>) + (|0> - |1>))/2
(-|0> - |1> + |0> - |1>)/2
(-2|1>)/2
-|1>
The result will be 1 with a probability amplitude of -1, corresponding to a probability of 1.
So in practice, each qubit will probably be a single particle or something. With 8 qubits, you have 2^8 probability amplitudes that a classical computer would have to keep track of separately. Unfortunately, you can't go around doing just anything you want to these probability amplitudes, like manipulating them one by one, but manipulating them in certain ways can land you with a nice, fast algorithm, like Shor's algorithm, which can factor integers (which is useful for breaking certain types of codes) faster than any known classical algorithm. How does it work? I have no idea
A theorem of quantum mechanics is that you can't perfectly copy a quantum state as that would allow you to measure the energy of one copy and the time of the other, thus violating the uncertainty principle. In practise what happens is that the two systems become entangled so that a measurement on one of them will instantly disrupt the state of the other. Thus your quantum UNIX would have the 'ln' command but not 'cp' ( 'cp -l' is ok ). Even more amusing is that this mandates that the disruption is non-deterministic. If it wasn't you could use it to transmit information and energy quicker than the speed of light, which is prohibited by relativity. So, if you thought lawmakers had trouble understanding how computers work, just wait until they get to deal with the question of who is liable for causing the de-coherence of a quantum system ( hint: you can't prove it unless you caused it ). Bring on the lawyers :P
now, everytime you try to measure the release date, it will change!
A goal is a dream with a deadline
The main roadblock to keeping the gates unitary (i.e. keep the error rate low) is to have the switching occur faster than the decoherence time (the timescale over which the delicate superposition decoheres into a random probabilistic mixture). This is certainly a difficult issue to solve, but in principle it is possible. The small-scale quantum computers that have been built to date were able to solve small problems deterministically.
As a practical point, it may turn out to be very difficult to build a quantum computer... but as far as I know the intended designs of quantum computers are not to yield probabilistic answers and then to average them, but to maintain coherence long enough that the final answer is deterministic, with an acceptably small error rate.
It's all so obvious now!
If fate makes you a motorcycle, you become a motorcycle.
Even checking "Read Only" would irreversibly damage the contents
Maybe this research is funded by Microsoft.
Pavlov wouldn't be so famous if he'd used a can opener instead of a bell.
Were you a g*ddammned hall monitor or something in a past life?
What are you talking about? I replied to a non-sequitur about doing "something".
I did "soemthing".
I posted.
About a funny idea that occurred from mis-reading the post. Quantum DRM is a possible misapplication of the crypto possibilities in quantum computing. But the existence of quantum RAM suggests that the problem might be moved into an area that was not previously accounted for in the speculation.
I was appealing for folks with insight to explore this possibility, or to demonstrate where this was tangential or irrelevant to core cryptography problems.
That is not nonsensical.
Oh, and I think you might need to get laid, or something.
"Flyin' in just a sweet place,
Never been known to fail..."