These larger quantum superpositions are usually entangled, meaning that the measurements of the individual qubits will be correlated. Quantum entanglement can be thought of as an invisible wiring between particles that cannot be replicated in classical physics, a wiring that Einstein called “spooky action at a distance.” In our trapped-ion experiments, for example, each electrically levitated ion behaves like a microscopic bar magnet; the qubit states of 1 and 0 can correspond to two possible orientations of each atomic magnet (say, up and down). Laser cooling, which drains kinetic energy from atoms by scattering photons, brings the ions almost to rest within the trap. Because the ions reside in a vacuum chamber, they are isolated from the environment, yet the electric repulsion among them provides a strong interaction for producing entanglement. And laser beams thinner than a human hair can be targeted on individual atoms to manipulate and measure the data stored in the qubits.
Over the past few years scientists have performed many of the proof-of-principle experiments in quantum computing with trapped ions. Researchers have produced entangled states of up to eight qubits and have shown that these rudimentary computers can run simple algorithms. It appears straightforward (though technically very challenging) to scale up the trapped-ion approach to much larger numbers of qubits. Taking the lead from classical computers, this effort would involve sequencing a few types of quantum logic gates, each made up of only a few trapped ions. Scientists could adapt conventional error-correction techniques to the quantum world by using multiple ions to encode each qubit. Here the redundant encoding of information allows the system to tolerate errors, as long as they occur at a sufficiently low rate. In the end, a useful trapped-ion quantum computer would most likely entail the storage and manipulation of at least thousands of ions, trapped in complex arrays of electrodes on microscopic chips.
The first requirement for making a “universal” quantum computer—one that can perform all possible computations—is reliable memory. If we put a qubit in a superposition state of 0 and 1, with the ion’s magnetic orientation pointing up and down at the same time, it must remain in that state until the data are processed or measured. Researchers have long known that ions held in electromagnetic traps can act as very good qubit memory registers, with superposition lifetimes (also known as coherence times) exceeding 10 minutes. These relatively long lifetimes result from the extremely weak interaction between an ion and its surroundings.
The second essential ingredient for quantum computing is the ability to manipulate a single qubit. If the qubits are based on the magnetic orientation of a trapped ion, researchers can use oscillating magnetic fields, applied for a specified duration, to flip a qubit (changing it from 0 to 1, and vice versa) or to put it in a superposition state. Given the small distances between the trapped ions—typically a few millionths of a meter—it is difficult to localize the oscillating fields to an individual ion, which is important because we will often want to change one qubit’s orientation without changing that of its neighbors. We can solve this problem, however, by using laser beams that are focused on the particular qubit (or qubits) of interest.
The third basic requirement is the ability to devise at least one type of logic gate between qubits. It can take the same form as classical logic gates—the AND and OR gates that are the building blocks of conventional processors—but it must also act on the superposition states unique to qubits. A popular choice for a two-qubit logic gate is called a controlled not (CNOT) gate. Let us call the qubit inputs A and B. A is the control bit. If the value of A is 0, the CNOT gate leaves B unchanged; if A is 1, the gate flips B, changing its value from 0 to 1, and vice versa. This gate is also called a conditional logic gate, because the action taken on qubit input B (whether the bit is flipped or not) depends on the condition of qubit input A.
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Add CommentI^mz .... I = infinite ^ angle of mz = largest and smalles measurement programmed ga programming
Reply | Report Abuse | Link to thisIs the editor on vacation?
Reply | Report Abuse | Link to thisThis article starts minus the capital letter.
"...technological advances have dramatically boosted the..." Is that the beginning of the sentence? If so, why isn't the 't' capitalized??
Are we just throwing out the basic grammar rule book now? Shame on Sci Am. Don't publish if you aren't doing to do it right.
Quasimodo-Were you picked on a lot as a kid? The article is concise and informative. Get over yourself and take the benefit from this article that it most definitely offers. Besides I do not know what article you read but the capitalization and punctuation is fine. The sentence starts:
Reply | Report Abuse | Link to this"Over the past several decades technological advances have dramatically boosted the speed and reliability of computers."
So you have made an even bigger fool of yourself than I first assumed.
**The field of quantum information science promises to radically change the rules of computing.** As scientists still work on small size quantum gates, they cannot afford arguing about new computing rules at present. Designing the new rules simply belongs to another realm of understanding. Similarly, what evolutionism could prove so far is so inexistent that its early allegations about origin of life are boldly presumptuous. So far, origin of life is not a scientific debate.
Reply | Report Abuse | Link to thisSciMike,
Reply | Report Abuse | Link to thisProfessionals write professionally, got it? Too bad if you don't. You answered my question with a question. That's pretty unprofessional.
Either answer my question, or hush up. My question had Nothing to do with the actual facts put forth in the body of the article. Grow up and smell the decade.
I have a question, if anyone here can help me out on this. Considering qubits that are based on the magnetic orientation of a trapped ion, as I understand it, in order to make a particle (say a proton) "flip" in a magnetic field from one orientation to another, we need to apply an amount of energy (by using a wave of particular frequency) that is exactly equivalent to the energy gap between the two spin states (orientations). So, how exactly is it possible to make the particle be in the superposition state? Do we apply half the energy or twice as much (which doesn't make sense), or what exactly do we do? I guess this is the whole point of quantum mechanics...but I dont really get it.
Reply | Report Abuse | Link to thisOh yeah, and something else regarding logic gates....maybe I misunderstood, but how is it possible to form classic logic gates like AND and OR gates using qubits? I mean, these gates are based on determinable deductive logic, but in quantum mechanics, there is always uncertainty (heisenberg's principle) and logic is based on probability (am I right?), so how is that possible?
Reply | Report Abuse | Link to thisIt is of certain intrigue how the evolutionary procedure of this technological branch would reach the ironic imminence of its possible outcomes, which will set forward a whole new perspective on the computational processes within modern electronics. But considering the constant repression the elite has over the introduction of ideas that can potentially compromise their agenda, this technology would still be far from reaching consumer applications.
Reply | Report Abuse | Link to thisOh yeah, and something else regarding logic gates....maybe I misunderstood, but how is it possible to form classic logic gates like AND and OR gates using qubits? I mean, these gates are based on determinable deductive logic, but in quantum mechanics, there is always uncertainty (heisenberg's principle) and logic is based on probability (am I right?), so how is that possible?
Reply | Report Abuse | Link to thisQuantum dot: Are you trying to understand how the gates work or are you just asking how classical gates can be used at all? If you are asking how a classical logic gate works in this situation I will explain that. The logic behind the gates (as I see it) works on a basic principle of quantum mechanics: when you measure something, it changes. Uncertainty doesn't apply in this instance. I see this as a similarity to the double slit experiment where a physical medium is used to measure a quantum state, which forces it to choose and orientation.
ID-based COMPLEX GATES : ID global approach holds the overall answer (God), to be verified in subsequent details. Conversely, evolutionism starts from details (fossils), with no serious intention of reaching a significant answer(Void). Similarly, quantum gates computing rules are determined from software design, while Hardware approach deals with details void of meaning. For instance, the elementary quantum gate described here may get two meanings: CNOT (already described) and XOR. Let us call D1, D2 respectively the first and second data of the gate and A the XOR result. If D1 is 1 and D2 is 1, D2 holds the result as 0: A=D2=0**D1=1, D2=0: A=D2=1** D1=0, D2=1: A=D2=1 **D1=0, D2=0: A=D2=0 ** It is therefore software level interpretation (as XOR or CNOT) that gives the gate its actual meaning, hardware approach simply describing the gate maravellous potential.
Reply | Report Abuse | Link to thisQuasimodo , I find it hilarious that your incorrect rant about an error in their article, is followed with this statement by you:
Reply | Report Abuse | Link to this"Shame on Sci Am. Don't publish if you aren't doing to do it right. "
Hilarious! Shame on you, don't comment if you aren't going to do it correctly!
Kevino819, thank you for your response. You mentioned the basic quantum mechanical principle of: when we measure something, it changes, but what I was trying to say is I just don't understand how its possible to run an algorithm or a program, or to program the logic gates themselves, when the outcome is unknown and based on the measurement, there is no expected result, do you see what I'm trying to say? I mean, its like trying to use logic gates for something where there is no logic.
Reply | Report Abuse | Link to thisWith the AND and OR gates, you'd do it kinda like it's done like it's done in a normal computer. AND: measure two qubits. if they're both in the 1 state, then your AND thing gets a 1 as a return. for the OR gate you'd do the same thing but return a 1 if either qubit was a 1.
Reply | Report Abuse | Link to thisOh, and i think that the qubits can use any of their properties as the data carrying ones, it doesn't have to be their magnetic alignment, it can be anything.
Something that would be very cool about this technology (if i'm assuming correctly) is that you could entangle particals and seperate them between a pair of machines, creating a wireless connection between the two of infinite range. It would work in a tunnel, underground, on the moon! Or, you could go a stage further and link all the processors of all Quantum computers in the world so that they share their computing power amongst all the users!
I will be the first one implements commercial Qcomputer
Reply | Report Abuse | Link to thisI will be the first one implements commercial Qcomputer.
Reply | Report Abuse | Link to thisIt is a very nice thing to see your excellent work and I like your article very much. With your rich knowledge, we can learn more from your wonderful post. Thanks so much.
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What's most interesting is how conditional programs might be able to use probabilistic results of conditional tests - will this be accomplished through probabilistic branch functions? 'If taxable income >72% Then 48% Perform tax calculation...'
Reply | Report Abuse | Link to thisQuasi, SciMike was right. You were and are wrong. And, oddly, you persisted in being wrong.
Reply | Report Abuse | Link to thisI have been puzzled of late. With the Higgs Boson "found" does that mean we have M-theory to ponder. I mean the standard model is vindicated and there is a bridge to quantum effects within the standard model. If this is correct the M-theory is valid; please correct me if I have strayed. What I want to know is what does an electron, for instance, look like in any of the other 7 dimensions and can that be computed using this method. Can we develop sensors and emitters to augment our simple four dimensions? Does that form the basis of what dark matter is? This has had me in a transfixed state since the Higgs was defined. If anyone can elucidate more please feel free!
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