How does a quantum computer work?

We know that a classical computer processes elementary information, bits, which can only present one of two possible states: 0 or 1. This is the binary language. The revolution proposed by quantum computing is to replace these bits with quantum bits, or q (u) bits for short, which can take a much wider set of values. Indeed, quantum physics, with its superposition principle, allows a state to be a “mixture ” of other states. Thus, a qbit can take the values ​​0 or 1, but also a state constitutes 10% of 0 and 90% of 1, or any other combination. This means that when we measure the value of qbit, we have a 10% chance of finding 0 and 90% of finding 1. Basically, qbit can be in both state 0 and state 1 ( it is a somewhat cavalier way to express a precise mathematical result and we must not put too much weight in this interpretation). The richness offered by this principle is however paid by the introduction of an uncertainty in the measurement of the qbit. A little more concretely, with 4 bits, a conventional computer can treat a state among 24 or 16 different states: 0000, 0001, 0010, 0011, etc. In a quantum computer, the four qbits could be in a supersposition of all these states. In this situation, the advantage of the quantum computer is that it can simultaneously process the 16 states. Quantum computers equipped with N qubit processors can manage 2N different information simultaneously! They calculate so N times faster than a conventional computer because they are able to perform these calculations in parallel! The number of qubits therefore exponentially increases the power of parallel work. It is thus easy to calculate that a quantum computer of 300 qbits could handle about 1090 informations, more than the number of Composition of an atom: protons, neutrons and … “data-image = ” “data-more = ” Read more “data-number = ” “data- title = “Atom ” data-tooltip = “” data-url = “http: // ” href = “http : // “> atoms in history The history of the universe begins some 13.7 billion years ago in a Extremely dense and hot soup … The laws of physics as we know them … “data-image = ” 1557798396_80921_univers.jpg “data-more = ” Read more “data-number = ” “data-title = ” Universe “data-tooltip = ” “data-url = ” http: / / ions / astronomy-universe-15239 / “href = ” http: // “> Observable Universe. Today, however, we are still far from being able to manage as many states and the most powerful quantum computer prototypes work best with 7 qubits, the equivalent of a 7-bit processor but massively parallel Managing Decoherence When a quantum system is in a quantum state that is a superposition of several classical states, we speak of a coherent state, and the phenomenon is referred to as “entanglement or quantum nesting”. But one of the reasons why it is very difficult to produce entangled states on macroscopic scales is that as soon as a quantum system interacts with its environment, it “decodes” and falls into one. The potential power of quantum computers depends on the parallelism properties present in the state of quantum nesting. The phenomenon of decoherence represents a major obstacle for the manufacture of such computers because it means a return to conventional states, but also a loss of information and a high risk of errors in the calculations. the measure of the value contained in the qbits breaks the superposition, and we find ourselves in the same situation as in the classic case: each qbit contains the value 0 or 1 after the measurement! We seem to lose all of a sudden all the advantages offered by quantum properties One of the great difficulties of this field is thus to find algorithms specific to quantum computers and which make it possible not to lose the result of the computation when one reads it … “Find the resultBut this n is not the only problem that physicists have to face. Since the quantum computer works in a multidimensional mathematical universe, the results of a computation performed in parallel are distributed in as many parallel or different universes. What is the practical consequence of this phenomenon? The use of nested states for a given series of calculations means that the final solution of the calculation is delocalized in the set of Wave Phenomena due to … “data-more = ” Read more “data-number = ” “data-title = ” Interference “data-tooltip = ” “data-url = ” interference-1012 / “href = ” http: // “> interferences created by the different classical steps.In practice, this means that if you look at a particular calculation, the equivalent of an intermediate state, you run the risk of disturbing the other calculations and of making the interference disappear, which will in some ways cause the “crash” of quantum computation.


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