Introduction to quantum computer operation

The massive amount of processing power generated by computer manufacturers has not yet been able to quench our thirst for speed and computing capacity. In 1947, American computer engineer Howard Aiken said that just six electronic digital computers would satisfy the computing needs of the United States. Others have made similar errant predictions about the amount of computing power that would support our growing technological needs. Of course, Aiken didn’t count on the large amounts of data generated by scientific research, the proliferation of personal computers or the emergence of the Internet, which have only fueled our need for more, more and more computing power.

Will we ever have the amount of computing power we need or want? If, as Moore’s Law states, the number of transistors on a microprocessor continues to double every 18 months, the year 2020 or 2030 will find the circuits on a microprocessor measured on an atomic scale. And the logical next step will be to create quantum computers, which will harness the power of atoms and molecules to perform memory and processing tasks. Quantum computers have the potential to perform certain calculations significantly faster than any silicon-based computer.

Scientists have already built basic quantum computers that can perform certain calculations; but a practical quantum computer is still years away.

You don’t have to go back too far to find the origins of quantum computing. While computers have been around for the majority of the 20^th century, quantum computing was first theorized less than 30 years ago, by a physicist at the Argonne National Laboratory. Paul Benioff is credited with first applying quantum theory to computers in 1981. Benioff theorized about creating a quantum Turing machine. Most digital computers, like the one you are using to read this article, are based on the Turing theory.

Defining the quantum computer

The Turing machine, developed by Alan Turing in the 1930s, is a theoretical device that consists of tape of unlimited length that is divided into little squares. Each square can either hold a symbol (1 or 0) or be left blank. A read-write device reads these symbols and blanks, which gives the machine its instructions to perform a certain program. Does this sound familiar? Well, in a quantum Turing machine, the difference is that the tape exists in a quantum state, as does the read-write head. This means that the symbols on the tape can be either 0 or 1 or a superposition of 0 and 1; in other words the symbols are both 0 and 1 (and all points in between) at the same time. While normal Turing machine can only perform one calculation at a time, a quantum Turing machine can perform many calculations at once.

Today’s computers, like a Turing machine, work by manipulating bits that exist in one of two states: a 0 or a 1. Quantum computers aren’t limited to two states; they encode information as quantum bits, or qubits, which can exist in superposition. Qubits represent atoms, ions, photons or electrons and their respective control devices that are working together to act as computer memory and a processor. Because a quantum computer can contain these multiple states simultaneously, it has the potential to be millions of times more powerful than today’s most powerful supercomputers.

This superposition of qubits is what gives quantum computers their inherent parallelism. According to physicist David Deutsch, this parallelism allows a quantum computer to work on a million computations at once, while your desktop PC works on one. A 30-qubit quantum computer would equal the processing power of a conventional computer that could run at 10 teraflops (trillions of floating-point operations per second). Today’s typical desktop computers run at speeds measured in gigaflops (billions of floating-point operations per second).

Researchers at IBM — Almaden Research Center — developed what they claimed was the most advanced quantum computer. The 5-qubit quantum computer was designed to allow the nuclei of five fluorine atoms to interact with each other as qubits, be programmed by radio frequency pulses and be detected by NMR instruments similar to those used in hospitals. Led by Dr. Isaac Chuang, the IBM team was able to solve in one step a mathematical problem that would take conventional computers repeated cycles. The problem, called order-finding, involves finding the period of a particular function, a typical aspect of many mathematical problems involved in cryptography.

Qubit control

Computer scientists control the microscopic particles that act as qubits in quantum computers by using control devices.

Ion traps use optical or magnetic fields (or a combination of both) to trap ions.

Optical traps use light waves to trap and control particles.

Quantum dots are made of semiconductor material and are used to contain and manipulate electrons.

Semiconductor impurities contain electrons by using “unwanted” atoms found in semiconductor material.

Superconducting circuits allow electrons to flow with almost no resistance at very low temperatures.

Today’s quantum computers

Quantum computers could one day replace silicon chips, just like the transistor once replaced the vacuum tube. But for now, the technology required to develop such a quantum computer is beyond our reach. Most research in quantum computing is still very theoretical.

The most advanced quantum computers have not gone beyond manipulating more than 16 qubits, meaning that they are far from practical application. However, the potential remains that quantum computers one day could perform, quickly and easily, calculations that are incredibly time-consuming on conventional computers. Several key advancements have been made in quantum computing in the last few years. Let’s look at a few of the quantum computers that have been developed.

2000. In March, scientists at Los Alamos National Laboratory announced the development of a 7-qubit quantum computer within a single drop of liquid. The quantum computer uses nuclear magnetic resonance (NMR) to manipulate particles in the atomic nuclei of molecules of trans-crotonic acid, a simple fluid consisting of molecules made up of six hydrogen and four carbon atoms. The NMR is used to apply electromagnetic pulses, which force the particles to line up. These particles in positions parallel or counter to the magnetic field allow the quantum computer to mimic the information-encoding of bits in digital computers.

2001. Scientists from IBM and Stanford University successfully demonstrated Shor’s Algorithm on a quantum computer. Shor’s Algorithm is a method for finding the prime factors of numbers, which plays an intrinsic role in cryptography. They used a 7-qubit computer to find the factors of 15. The computer correctly deduced that the prime factors were 3 and 5.

2005. The Institute of Quantum Optics and Quantum Information at the University of Innsbruck announced that scientists had created the first qubyte, or series of 8 qubits, using ion traps.

2006. Scientists in Waterloo and Massachusetts devised methods for quantum control on a 12-qubit system. Quantum control becomes more complex as systems employ more qubits.

2007. Canadian company D-Wave demonstrated a 16-qubit quantum computer. The computer solved a sudoku puzzle and other pattern matching problems. The company claims it will produce practical systems. Skeptics believe practical quantum computers are still decades away, that the system D-Wave has created isn’t scaleable, and that many of the claims on D-Wave’s Web site are simply impossible.

If functional quantum computers can be built, they will be valuable in factoring large numbers, and therefore extremely useful for decoding and encoding secret information. If one were to be built today, no information on the Internet would be safe. Our current methods of encryption are simple compared to the complicated methods possible in quantum computers. Quantum computers could also be used to search large databases in a fraction of the time that it would take a conventional computer. Other applications could include using quantum computers to study quantum mechanics, or even to design other quantum computers.

But quantum computing is still in its early stages of development, and many computer scientists believe the technology needed to create a practical quantum computer is years away. Quantum computers must have at least several dozen qubits to be able to solve real-world problems, and thus serve as a viable computing method.

 

Notes

To quench our thirst – утолить нашу жажду; similar errant predictions – подобные расплывчатые предсказания; have only fueled our needs – дало новый импульс нашим потребностям; will harness the power of atoms and molecules – задействуют энергию атомов и молекул; is credited with first applying quantum theory – признается первым, кто применил квантовую теорию; superposition – совмещенное состояние; multiple states – многократные состояния; trans-crotonic acid – транс-кротонная кислота; fluorine – фтор; prime factors – основные множители; ion trap – ионная ловушка.

 

Computerized tomography

It is an imaging technique which uses an array of detectors to collect information from a beam that has passed through an object (for example, a portion of the human body). The information collected is then used by a computer to reconstruct the internal structures, and the resulting image can be displayed – for example, on a television screen. The technique relies on the fact that wave phenomena can penetrate into regions where it is impossible or undesirable to introduce ordinary probes.

In medicine, computerized tomography represents a noninvasive way of seeing internal structures. In the brain, for example, computerized tomography can readily locate tumors and hemorrhages, thereby providing immediate information for evaluating neurological emergencies. Another advantage of computerized tomography is three-dimensional reconstruction. It is most useful in cases of fracture of the hip or facial bones, helping the surgeon to do reconstructive surgery. Other medical imaging techniques that make use of computerized tomographic methods include magnetic resonance imaging, positron emission tomography, and single-photon emission tomography.

After the success of computerized tomography in medicine, its possibilities in other fields were quickly realized. In the earth, atmospheric, and ocean sciences it has supplemented, but no means replaced, older methods of remote sensing. Seismic tomography is now an important tool for investigating the deep structure of the Earth, testing theories such as plate tectonics, and exploring for oil. Ocean acoustic tomography is applied to physical oceanography, climatology, and antisubmarine warfare. Atmospheric tomography finds applications to weather, climate and the environment.

Notes

Plate tectonics – тектоника плит (современная геологическая теория о движении земной коры и мантии)

Character recognition

The process of converting scanned images of machine-printed or handwritten text (numerals, letters, and symbols) into a computer-processable format also known as optical character recognition (OCR). A typical OCR system contains three logical components: an image scanner, OCR software and hardware, and an output interface. The image scanner optically captures text images to be recognized. Text images are processed with OCR software and hardware. The process involves three operations: documents analysis (extracting individual character images), recognizing these images (based on shape), and contextual processing (either to correct misclassifications made by the recognition algorithm or to limit recognition choices). The output interface is responsible for communication of OCR system results to the outside world.

Commercial OCR systems can largely be grouped into two categories: task-specific readers and general-purpose page readers. A task-specific reader handles only specific document types. Some of the most common task-specific readers read bank checks, letter mail, or credit-card slips. General-purpose page readers are designed to handle a broader range of documents such as business letters, technical writings and newspapers.

Notes

General - purpose page reader – универсальное устройство для считывания страниц

 

Plastic logic e-newspaper

Plastic Logic, a spin-off company from the Cambridge University’s Cavendish Laboratory, has recently released its design of a future electronic newspaper reader. This lightweight plastic screen copies the appearance, but not the feel, of a printed newspaper. This electronic paper technology was pioneered by the E-Ink Corporation and is used in the current generation Sony eReader and Amazon.com’s Kindle. Plastic Logic’s device, yet to be named, has a highly legible black-and-white display and a screen more than twice as large compared to current versions available on the market.

Plastic Logic’s new device has an A4 sized display, can be continually updated via a wireless link, and can store and display hundreds of pages of newspapers, books, and documents. Richard Archuleta, the chief executive of Plastic Logic, said the display was Amazon Kindle sufficiently large enough to match a newspaper’s layout. “Even though we have positioned this for business documents, newspapers are what everyone asks for,” said Archuleta.

Another company vying to control the e-newspaper market is the Hearst Corporation. They own 16 daily newspapers, including the Houston Chronicle, the San Antonio Express, and the San Francisco Chronicle. Hearst was also an early investor in E-Ink, using this technology and to distribute electronic versions of some papers on Amazon’s Kindle.

The advancement of colour displays with moving images and interactive clickable advertisements would be available within a few more years. However, the ideal format of the flexible display which could be rolled or folded like a newspaper still has many years of development ahead.

At E-lnk’s headquarters recently, a demonstration was held showing prototypes of flexible displays that exhibit rudimentary colors and animated images. “By 2010, we will have a production version of a display that offers newspaper like colour,” said Peruvemba. He also expects technology allowing users to write on the screen and view videos to be available within the next few years.

E-lnk’s technology, commonly known as electronic paper (e-paper), is different from liquid-crystal display (LCD) used in modern computer monitors and televisions. This e-paper technology does not use a backlight and consumes power only when the content of the display changes. Contrasting to current display panels, which are barely visible in strong light, the e-paper’s display will look even brighter in daylight.

Compared to Amazon’s Kindle, Plastic Logic’s first display is 2.5 times larger and is only one-third of the Kindle’s thickness. However, it weighs two ounces more than Kindle, even though it uses a flexible, lightweight plastic as its cover. The display is expected to be on sale in the first half of 2009, according to the company.

Notes

Spin-off company - фирма, отделившаяся от материнской компании (с целью коммерческой реализации нового научно-технического достижения); Amazon Kindle is a software and hardware platform for reading electronic books (e-books), first launched in the United States on November 19, 2007. newspaper’s layout – формат газеты; another company vying - еще одна компания претендует; liquid-crystal display - жидкокристаллический дисплей

 

Embedded computers

The most common form of computer in use today is the embedded computer. Embedded computers are small, simple devices that are used to control other devices — for example, they may be found in machines ranging from fighter aircraft to industrial robots, digital cameras, and children’s toys.

A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets by dropping bombs. Fighters are comparatively small, fast, and maneuverable. Many fighters have secondary ground-attack capabilities, and some are dual-rolled as fighter-bombers; the term “fighter” is also sometimes used colloquially for dedicated ground-attack aircraft. Fighter aircraft are the primary means by which armed forces gain air superiority over their opponents above a particular battle space. Since at least World War II, achieving and maintaining air superiority has been a key component of victory in most modern warfare, particularly conventional warfare between regular armies (as opposed to guerrilla warfare), and the acquisition, training and maintenance of a fighter fleet represent a very substantial proportion of defense budgets for modern militaries.

Today is the age of the fifth-generation fighters which are characterized by being designed from the start to operate in a network-centric combat environment, and to feature extremely low, all-aspect, multi-spectral signatures employing advanced materials and shaping techniques. They have multifunction AESA radars¹ with high-bandwidth, low-probability of intercept (LPI) data transmission capabilities. IRST sensors² are incorporated for air-to-air combat as well as for air-to-ground weapons delivery. These sensors, along with advanced avionics, glass cockpits, helmet-mounted sights, and improved secure, jamming-resistant LPI datalinks³ are highly integrated to provide multi-platform, multi-sensor data fusion for vastly improved situational awareness while easing the pilot's workload. Avionics suites rely on extensive use of very high-speed integrated circuit (VHSIC) technology, common modules, and high-speed data bases. Other technologies common to this latest generation of fighters includes integrated electronic warfare system (INEWS) technology, integrated communications, navigation, and identification avionics technology, centralized “vehicle health monitoring” systems for ease of maintenance, and fiber optics data transmission. Overall, the integration of all these elements is claimed to provide fifth-generation fighters with a “first-look, first-shot, first-kill capability”.

 

Notes

¹ AESA radars ― An Active Electronically Scanned Array (AESA), also known as active phased radar is a type of radar whose transmitter and receiver functions are composed of numerous small transmit/receive (T/R) modules. AESA radars feature short to instantaneous (millisecond) scanning rates and have a desirable low probability of intercept.

²IRST sensors ― An infra-red search and track (IRST) system (sometimes known as infra-red sighting and tracking) is a method for detecting and tracking objects which give off infrared radiation such as jet aircraft and helicopters.

³LPI datalinks ― Low-Probability-of-Intercept datalinks

Avionics – авиационная радиоэлектроника; embedded computer – встроенный компьютер; fighter aircraft – самолет-истребитель; combat – бой; bomber – бомбардировщик; colloquially – в просторечии; to maintain – поддерживать; warfare – война; guerrilla warfare – партизанская война; acquisition – приобретение; glass cockpit – стеклянная кабина; jam – заклинивание, заедание; fusion – сплав, слияние; awareness – понимание; workload – рабочая нагрузка; to feature – показывать