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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."
Noah inquired.
Should the first quantum OS be M$ or Linux? :) I like to watch people argue about OS's. Makes me smile.
Let there be light, and there was "1".
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
This was covered on New Scientist and IndiaTimes a few days ago. Their articles:
-New Scientist
-IndiaTimes
Wow...
I was just going to look for information on Quantum Computing and I thought that I might as well refresh Slashdot too...
Sleep is futile.
"a 5 qubit register should be enough for anyone"
What is the advantage of using caesium?
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.
definition of qubit: The quantum computing analog to a bit. Qubits exhibit superposition. Thus, unlike normal bits, qubits can be both 1 and 0 at the same time.
thankyou NTN
Very small scale.
But it's not the scale that matters, it's the fact that it has been done. The problem with any QC related operation is the inherent difficulty -- in terms of having redundancy, storage, observation and retrieval.
That's why you keep hearing these things about quantum entanglement for 5 qubits and registers and the like. It's not the scale, it's the fact that people have been able to do them.
The problem is that a lot of things are THEORETICALLY possible in QC, but have not been practically achievable. Often times, people find that although it is theoretically possible, it's not realizeable due to some problem or the other. And then, further studies would prove that there are variables that people hadn't considered.
So, this would mean that we can store observed states -- in some way that can be copied and retrieved -- which is a big leap.
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>.
I got 5 caesium atoms free from Ron Popeil when I ordered my Showtime Rotisserie! They came in a seperate package from the steak knives. That's probably where these scientists got their's. That's why they used five atoms I suspect. To bad they didn't have money to buy the second Rotisserie and get a ten atom computer. I couldn't find a laser standing wave generator on Ron's site though. hmmmm.
From the theorist's perspectice it doesn't really matter how you implement this stuff - if it works, all implementations are equivalent.
At the current stage it is very reasonable to explore all possible routes to a QC (atoms, ions, photons, quantum dots, superconductors etc, a nice and readable uptodate overview is given in the Quantum Computation Roadmap): first, since it is not clear which will turn out to be most successful and second, because along the way lot of interesting physics can be expected from the coherent control of well isolated physical systems.But of course ther are (and will remain) technical advantages of certain implementations. I do not think that currently anybody knows what the most promising physical system is. Trapped ions are probably most advanced at the moment. Compared to them neutral atoms in optical lattices might two advantages: optical lattices appear to be rather "scalable", i.e., one might go beyond 5 qubits rather quickly, once complete coherent control has been demonstrated. (In a linear ion trap there will be difficulties to go beyond 10-20 ions, though very promising ways around these difficulties have also been demonstrated.) On the other hand, using neutral atoms (rather than charged ions) may make the qubits less susceptible to stray fields and other sources of decoherence.
Qubit.
/kyoobit/ ) is a unit of quantum information. That information is described by state in a 2-level quantum mechanical system, whose two basic states are conventionally labeled |0> and |1>(pronounced: ket 0 and ket 1). A pure qubit state is a linear quantum superposition of those two states. This is significantly different from the state of a classical bit, which can only take the value 0 or 1.
A qubit is not to be confused with a cubit, which is an ancient measure of length.
A qubit (quantum + bit; pronounced
A qubit's most important distinction from a classical bit, however, is not the continuous nature of the state (which can be replicated by any analog quantity), but the fact that multiple qubits can exhibit quantum entanglement. Entanglement is a nonlocal property that allows a set of qubits to express superpositions of different binary strings (01010 and 11111, for example) simultaneously. Such "quantum parallelism" is one of the keys to the potential power of quantum computation.
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Quantum cryptography
From Wikipedia, the free encyclopedia.
Quantum cryptography currently has two aspects. The first is quantum key exchange, a method for securing communications based on quantum mechanics. The second is the conjectured effect of quantum computing on cryptanalysis, although it is currently, like quantum computing itself, only a theoretical concept.
The basic idea in quantum key exchange is to use the "noisy" properties of light to render incoherent an image that acts to complement a secret key. This image can be represented in a number of ways, but the ability to decode that image rests upon an understanding of how it was made. No way to intercept the transmission without changing it is possible, so key information can be exchanged with great confidence it has been transmitted secretly.
Using quantum superposition as a part of the computation, quantum computing will considerably extend the reach of cryptanalysis, making brute force key space searches much more effective -- if such computers ever become possible in actual practice.
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NOTE: Please read the actual wikipedia articles. They have TONS of hyperlinks with full explanations!
We have to recalibrate the lateral baffles, and rotate the shield harmonics! Ziggy swears you should have leaped by now!
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.
They almost have a qubyte! Think of the power!!
Well.. maybe. Or Maybe not. But Definitely not sort of.
I got 5 caesium atoms free from Ron Popeil when I ordered my Showtime Rotisserie!
It's not real caesium, though! It's qubic zirconium...
Ooh, a sarcasm detector. Oh, that's a real useful invention.
So do you program it using QBasic?
For example, one qbit setup is to use a helium superfluid, which naturally bonds electrons to the surface. The bound electrons can then be controled with a combination of microwave radiation and an electric potential from wafer posts under the fluid. Each electron (qbit) sits on top of a post, which are spaced just a few nm apart. The system is still being developed, but the nice thing is once they get it to work, they can just build a large wafer holding millions of qbits.
However, the huge problem with the above example is that it needs to run at about 50 mK, which is very close to absolute zero and requires a dilution fridge, which is a 6 foot tall cylinder. There are similar (though more complicated) limitations to the laser trapping methods.
For a commercial unit I suppose the QC wafer, microwave source, and dilution fridge could be packaged together nicely, but it is still 6 feet tall, heavy, not well suited for a house. Even if it were possible to make one small enough, there are currently no real benefits for a home user unless they really wanted to find elements in a large array or crack PGP codes... I suppose the first computers were also only suited for a lab environment and scientists probably thought the average person would never need a computer either, so who knows what will develop in the next 50 years...
IMNSHO, It's not really a 5-qubit register until you have interaction between the bits. That is their next step, but until then, it just doesn't count. The reason is that, other than the third "indeterminate" state that randomly returns "1" or "0" (which they also do not appear to have tested), without interaction between bits they might as well be classical bits. There is no computing advantage (other than true-random number generation) without the interaction. If they demonstrated the random-number generation capacity, I would admit that they have 5 1-qubit registers. But I won't give them credit for a 5-qubit register without demonstrating interaction between bits.
Mathematics is not a crime.
"Qomputing" (qubit computing, get it?) is pursued independently across the globe, with separate teams reporting breakthrus in different pieces of the puzzle. One team has produced quantum entanglement, using "spooky action at a distance" to offer apparently instant communication between terminals. If each of these components in its distant lab were entangled in a quantum net, we'd get a qomputer built from the start to network in parallel while computing literally in parallel. Linux's unix heritage shows the compelling momentum derived from including networking from the beginning of the platform. Qomputing is born in the age of the network: entangled networks are natural midwives and gossips for a new qomputing qommunity.
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make install -not war
Disclaimer: I'm a graduate student doing research on quantum computing in optical lattices. I'm not affiliated with the group that published this article.
This result is quite exciting, because it demonstrates the feasibility of some of the techniques necessary for an optical lattice-based quantum computer. Imagine taking their 1-D lattice and turning it into a 3-D lattice, with about 30 atoms in each direction. That's a whole lot of qubits...
So what are the next steps?
1) A new means of addressing atoms (selecting one or two atoms on which to perform operations while excluding the rest) is necessary. Their magnetic gradient technique works fine for a small 1-D lattice, but it would likely be impractical for a large 3-D lattice (Maxwell's equation div B = 0 gives one major obstacle, which would require fancy tricks to overcome).
2) One and two-qubit gates need to be demonstrated using an appropriate addressing scheme.
3) Error correction, which would likely require quantum non-demolition measurements to check to see if an atom had been lost from a lattice site. Translation: we need to be able to measure if we've lost an atom from a lattice site, without disturbing the atom's state (i.e. measuring whether it's |0> or |1>).
4) Full-blown fault-tolerant computation.
My group plans to solve (1) using an addressable optical lattice. What that means is that the lattice spacing is sufficiently large that a laser can be focused on an individual atom (in 3-D, two lasers in orthogonal directions would be used). I'm currently doing simulations of one-qubit gates in this scheme.
That brings me to my question for slashdot: Some of the simulations I'll be doing (specifically, studying decoherence in the one and two qubit gates) will be very computationally intensive. They're also embarrassingly parallel, as they're essentially quantum Monte Carlo simulations. Would people be interested in a BOINC-based distributed computing project (a la SETI@home) to help develop quantum computers? If so, what kinds of things would help you get involved? Would you be interested in helping develop the software (it's C++)?
I probably won't be at that stage for another six months to a year, but it would be helpful to me to start planning now. I have just (last night) completed the core simulation engine, and would need to add code for decoherence, as well as adapt it to BOINC. The code will be GPL'd, of course.