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German Scientists Create 5 qubit Quantum Register
CMan0 writes "In the University of Bonn, a team of scientists has built a 5 qubit register, using cesium atoms trapped by a laser-beam grid, The Register reports. They've been able to install an empty 5 bit register(i.e. all bits 0), change two of them to 1, and later read those 1s back. The next goal is to create an interaction between 2 bits. The full scientific article can be found here in PDF format."
This was covered on New Scientist and IndiaTimes a few days ago. Their articles:
-New Scientist
-IndiaTimes
It'll be both until you boot it.
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Some people are good with words, others,
"a 5 qubit register should be enough for anyone"
So in ten years I'll have to wear a lead apron and protective glasses when I turn on my new computer? New fashion trend for geeks that never shut their boxes off.
Actually, there was uncertainty.
;)
:-(
Upon further observation, it was known to have a probability of 1
On a serious note, this is awesome. With a 5 qubit entanglement and this, we might be able to build a primitive functional Quantum Computer, for the first time.
The team is now working to create a quantum gate in which two or more qubits of the register will interact in a controlled way.
Amazing. The beginnings of a first QC. We've memory, redundancy, processing capabilities and a lot more.
Now the only problem that remains is a suitable and reliable means of error correction - which is the biggest problem thus far in QC
Whilst I am sure this is a step forward there must still be a big step between creating a 5-qubit register and a 5-qubit entangled register. With what they have created can only do the same as a five bit digital computer, with the second you could <insert you favourite quantum hyperbole here>.
A qubit (for "quantum bit") is the basic information unit for a quantum computer (just as the classical bit is for classical computers). They are actually two-state quantum systems (just as ... Ok, I'm repeating myself :-))
The point is that quantum systems have properties which are not found in classical systems. For one, they cannot be just in the states "0" or "1" (in the usual notation for quantum states: |0> or |1>), but also in so called superpositions of those states. Such a superposition means that they are something like both states at the same time (remember Schrödinger's cat? That's exactly such a state, except that unlike atoms, cats cannot actually be brought into such a state). More importantly, such a superposition can extend over more than one qubit, in which case each single qubit doesn't have a defined quantum state at all, but only the whole set of qubit has. This is called entanglement.
Now, why is this so useful? Well, assume you create a set of, say, 8 qubits which are all "half zero, half one". And now you perform a normal calculation on them (but with quantum operations). Then you are actually performing the calculation on all 8-bit combinations, at the same time, i.e. for all numbers between 0 and 255. This remarkable effect is called quantum parallelism.
Now, of course there's a catch: You cannot read out more than one of the results (because reading out one destroys the superposition), and which one you get is essentially random. Ok, you now may think, I can effectively make the calculation just for one randomly selected number? So this is actually a disadvantage? Well, the point is that you can not just do "classical" calculations, but you can add operations which are not possible in classical computers. For example, there are several "half zero and half one" bit states, and you can do a quantum operation to convert one of them to |0> and one of them to |1>. Therefore you can extract properties of that result which depend not on just one of the results, but on several of them. And this allows you to actually reduce the numeric complexity of certain tasks. For example, you can search an unsorted database in O(sqrt(N)) time, instead of the classical O(N) time (N being the size of the database). The most famous algorithm is of course Shor's algorithm which allows factorizing large numbers in polynomial time, thus allowing to break public key encryption systems like PGP.
Now, there's not too much danger yet, since AFAIK the biggest number successfully factorized with a quantum computer is 15. But then, as long as 5 qubits are newsworthy, you cannot expect too much (imagine a message that someone managed to build a classical 5-bit computer!).
The Tao of math: The numbers you can count are not the real numbers.
NMR quantum computing as demonstrated by IBM has many drawbacks.
For these reasons, liquid state NMR is not be considered to be scalable. Nevertheless, the NMR people have amazing control over the operations (logic gates) they can perform, and these ideas may (and have) fed back to other implementations. Moreover, there are attempts to overcome the mentioned difficulties (while keeping some advantages of NMR) by using nuclear spins in cold solids following Kane's proposal).First, there's not a single quantum system doing the computation, but rather some 10^20 molecules in the liquid - and you need so many to generate a detectable signal.
Second, the NMR quantum register cannot be properly initialized, rather it is in a nearly random state with only a slight enhancement of "0" over "1". This is part of the reason why so many systems are needed and it prevents the currently realized systmes from displaying any entanglement.
Finally, it is not clear how to scale such a system (increase the number of nuclear spins on a molecule): the larger that number, the more difficult it is to address individual qubits.
Are we still going to use mouse? Or a cat with two buttons labeled as "alive" and "dead"?
There is a spark in every single flame bait point.