1. Summary
What is quantum computing?
Computing brings a small change in the computing paradigm that allows massive parallelism to be applied when calculating for significant computational gains, sacrificed in determinism of classical algorithms.
For this a quantum computer needs that the particles that are going to form the qubits that compose it can be in two states at the same time, requiring an almost total isolation and an environment that controls and avoids any possible interaction of the qubits with other particles or radiation, which makes it difficult to build currently real quantum computers that can become stable and this is the reason why a quantum computer with sufficient capacity has not yet been implemented, only prototyping that is progressing little by little.
2. Introduction
It is a different computing paradigm than classical computing. It is based on the use of qubits instead of bits, and it gives rise to new logical gates that make new algorithms possible.
2.1 Bits and qubits. Overlapping information
In classic computers the minimum amount of storable information is the bit. An atomic memory cell can store one of two possible discrete states, 0 or 1. The application of quantum mechanics to the concept of bit is what allows the birth of the quantum bit or qubit (quantum bit): a memory cell which can be in one of the two states (0 or 1), or in a certain superposition of both.
This means that with a register of N qubits, up to 2 ^ N different values can be represented. And doing an operation on a qubit register will be doing it on all the values that are superimposed on the register. This massive application of parallel calculations is what we can call, under Everett's interpretation, "operating on the infinite parallel universes", that is, on the different realities (or values) that the qubits register can contain at that time. As an example, if you have a 10-qubit register then that same register can store up to 1024 values at a time, that is, the superposition of all the possible values that the ten classic bits could take. By operating with that registry,This operation will be applied to all possible registry values, so in this case 1024 operations will be performed at the cost of a single one. It is clear that the power of the system will increase exponentially to the number of qubits that can be grouped in a register.
3. Origin of quantum computing
The idea of quantum computing arises in 1981, when Paul Benioff expounded his theory to take advantage of quantum laws in the computing environment. Instead of working at the level of electrical voltages, one works at the level of how much. In digital computing, a bit can only take two values: 0 or 1. By contrast, in quantum computing, the laws of quantum mechanics intervene, and the particle can be in coherent superposition: it can be 0.1 and it can be 0 and 1 at the same time (two orthogonal states of a subatomic particle). This allows several operations to be performed at the same time, depending on the number of qubits.
4. Features
While in the computation that we use today, each bit can appear in alternate and direct states at the same time, in quantum computing each bit becomes multiple states at the same instant. Thanks to this, we can exponentially reduce the time used by current algorithms. There is an architecture very similar to what we currently have, which has been very successful in the theoretical field and whose realization depends on the future implementation of a quantum computer.
Quantum scientists have made enormous theoretical advances in demonstrating that the drastic reduction of the computational resources required in the execution of algorithms is feasible, some of which require a great deal of computing power in the most advanced computers that exist today. Some of the theoretically very successful examples developed are the aforementioned search for prime factors, or searching unsorted databases. The theoretical basis of quantum computing is based on the interactions of the atomic world, as well as future implementations of quantum computers. In addition, it is one of the methods with the greatest future because it offers a range of enormous presentations, and can even duplicate the most advanced storage devices.
5. Quantum entanglement and teleportation
A surprising concept of quantum mechanics is the one known as quantum entanglement or entanglement whereby two particles of unknown state are linked so that, regardless of the distance at which they are, when the wave function of one of the particles collapses, the state of its interlocking counterpart will be determined to a greater or lesser extent, even when this other particle is in an independent system. This effect will be applied to the qubit, making the value that some of them depend on the value that we observe in others, allowing us to carry out this "filtering" of values that we are talking about, since observing a certain value in a register will completely condition the values that we can observe. in another record that is linked in the first one.
Quantum teleportation makes use of this principle, and allows us to retrieve the information that contains a qubit of unknown state anywhere far from the original qubit, thus transporting all the information that said qubit contained to another qubit. We will use the interlacing of two qubits as the transmission channel: we will operate the qubit that we want to transport with one of the interlaced qubits, causing a collapse of the information of both and obtaining two classic bits together with the interlaced qubit that is not collapsing. Those two classic bits can now be operated in conjunction with the interleaved qubit, allowing us to restore the information that contained the qubit to be transported. This allows us to send the information containing an unknown status qubit to another location,without losing the information and without risk that during the sending the qubit interacts with the ruined system the information it contains.
5.1 Examples of applications of quantum computing
Two interesting applications for quantum computing are presented below.
Shor's algorithm for factoring a number:
Currently, factoring integers into prime numbers is one of the greatest computational challenges in existence. The best known factorization algorithms do not solve the problem in an acceptable time, they have an efficiency of (O (e ^ (a * log (a)))), with n the size in numbers of the number, and the last practical result obtained supposed 18 months of calculation (in 50 years of "computing time") to factor a number of 200 figures.
This is used in the field of encryption, to create keys that involve knowing the factors of a large number to be decrypted.
In this case, quantum computing promises us great results, providing Shor's quantum algorithm, which transforms the problem of finding the prime factors of a number into the problem of finding the period of a certain function, and then makes use of the advantages of quantum computing to evaluate the function at all its points at once, finding the period of the function almost certainly, and achieving a saving in calculation time until reaching an efficiency of (0 (log (〖n)〗 ^ 3)).
It can be easily seen how the gain in this case between the classical algorithm and the quantum algorithm is of an abysmal difference.
Grover algorithm for searching a messy set:
We can find another example of the advantages of quantum algorithms in Grover's algorithm for searching for an element over a disordered set.
Classically, the search efficiency on a disordered set of size n is, of course, O (n). Grover's algorithm manages to improve this time to O (√n).
Although the gain may not seem as impressive as in the previous case, the applications are much more important since this can be used to accelerate any algorithm that is partially or completely based on an exhaustive search on the set of possible solutions.
Shor vs Alg. Classic
Shor vs Alg. Classic
Scientists
Hypercomputers (Beyond Turing).
Paul Benioff, Richard Feynman, David Deutsch, Lov Grove, Seith Lloyd, Michio Kaku, etc.
6. Advantages of quantum computing
In summary, the advantages of quantum computing are the massive application of parallel applications and the ability to provide new solutions to problems that cannot be covered by quantum computing due to its high computational cost.
However, despite the advantages outlined above, a quantum computer will only be efficient for a given range of tasks. This implies that there will be certain functions in which it will not be an advantage to use quantum technology over current classical computing.
6.1 Problems of quantum computing
One of the main obstacles to quantum computing is the problem of quantum coherence, which causes the loss of the unitary character of the steps of the quantum algorithm.
Otro de los problemas principales es la escalabilidad, especialmente teniendo en cuenta el considerable incremento en qubits necesarios para cualquier cálculo que implica la corrección de errores. Para ninguno de los sistemas actualmente propuestos es trivial un diseño capaz de manejar un número lo bastante alto de qubits para resolver problemas computacionalmente interesantes hoy en día.
7. Hardware para computación cuantica
Aun no se ha resuelto el problema de que hardware seria el ideal para la computación cuantica se ha definido una serie de condiciones que debe cumplir, conocida como la lista de Di Vinzenzo y hay varios candidatos actualmente.
Condiciones a cumplir.
El sistema ha de poder inicializarse, esto es, llevarse a un estado de partida conocido y controlado.
Ha de ser posibles manipulaciones a los qubits de forma controlada, con un conjunto de operaciones que forme un conjunto universal de puertas lógicas.
El sistema ha de mantener su coherencia cuantica a lo largo del experimento.
Ha de poder leerse el estado final del sistema, tras el cálculo.
El sistema ha de ser escalable: tiene que haber una forma definida de aumentar el número de qubits, para tratar con problemas de mayor coste computacional.
7.1 Transmisión de datos y procesadores
Científicos de los laboratorios Max Planck y Niels Bohr publicaron, en noviembre de 2005, en la revista Nature, resultados sobre la transmisión cuantica, usando la luz como vehículo, a distancias de 100 kilómetros. Los resultados dan niveles de éxito en las transmisiones del 70 %, lo que representa un nivel de calidad que permite utilizar protocolos de transmisión con auto corrección.
Actualmente se trabaja en el diseño de repetidores que permitirían transmitir información a distancias mayores a las ya alcanzadas.
En 2004, científicos del instituto de Física aplicada de la universidad de Bonn publicaron resultados sobre un registro cuántico experimental. Para ello utilizaron átomos neutros que almacenan la información cuantica, por lo que son llamados qubits por analogía con los bits. Su objetivo actual es construir una puerta cuantica, con lo cual se tendrían los elementos básicos que constituyen los procesadores que son el corazón de las computadoras actuales. Cabe destacar que un chip de tecnología VLSI contiene actualmente más de cien mil puertas de manera que su uso práctico todavía se presenta en un horizonte lejano
8. Tipos de computación
- – Computación clásica- ley de Moore.– Computación molecular (nano tecnología).-Más allá de las leyes física clásica. 2020 fin- almacenamiento 3D algunos años más.-Computación cuantica: algoritmos
9. Conclusión
- Fin de la computación clásicaDificultades de la computación cuanticaÁmbito de investigación.Posibles problemas para criptografía.
10. Referencias
- Baila Martínez, S. (2005). Computación Cuantica. http://www.sargue.netAlejo Plana, M.A. (2001). El ordenador cuántico. http://www.um.es/docencia/campoyl/cuantico.PDFSalas Peralta,P.J.(2006). Corrección de errores en ordenadores cuánticos. Revista española de física (Enero- Marzo, 2006).http://www.babab.com/no12/ordenadores.htmhttps://www.youtube.com/watch¿v=sXyCHdEbmcMhttp://www.microsiervos.com/archivos/ordenadores/ordenador-cuantico-apagado.htmlhttp://www.microsiervos.com/archivos/ordenadores/computacion-cuantica.htmlhttp://www.sociedadelainformacion.com/física/ordenadorescuanticos.htmhttp://www.amazings.com/ciencia/noticias/041102ª.html
11. Anexos
Concepto de computación cuántica
