quantum computing
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QUANTUM COMPUTING MENU
Introduction | The Need for QC | Basis of QC | The State of a QC | Qubit control | Quantam Gates
The Power of The QC | Quantum Aalgorithms | Saving the World | The Orion of QC
introduction
Behold the computer. The greatest, ultimate invention across multiple eras. The grand culmination of brilliant work by the greatest thinkers, scientists, engineers and inventors of the past century. How far have we come from the difference engine of Charles Babbage; to the first computer that occupied a whole room; to the multi-core, powerful compact computers on the shelves today. Very far indeed, right? Wrong! The high-speed, modern computer that sits in front of you is fundamentally no different than Babbage’s difference engine of nearly 200 years ago. The first computer used binary and the most modern computer today uses binary. All we have done in classical computer development is make them more compact and increase the number of transistors on a processor chip. Processing is still done using bits. A bit is still represented by 1’s and 0’s as it was centuries ago.
The classical computer , as the name implies, is classical. Step to a new breed of computing, one that differs radically from the very essence of computers and binary as we know it. An evolved breed…behold the quantum computer. A dynamic new fascinating field that is being pioneered as you read these words. Forget bits, binary and logic gates. Welcome to the world of Qubits, Quantum Gates and Quantum circuits & algorithms. Welcome to Quantum Computing!
the need for qc
Three things in life are certain - death, taxes, and man’s unquenchable thirst for computing power. The power of computers today depend upon the number of transistors on a chip. The more transistors, generally the more powerful the computer. Moore's Law states:
“The number of transistors on a microprocessor continues to double every 18 months”.
This means that by the year 2015 we will find that transistors on a chip will become so small that they will be measured on an atomic scale. As you discovered, quantum mechanics apply to the atomic world and the next logical step will be to create quantum computers, which will harness the power of atoms and molecules in computing. Quantum computers will be able to perform millions of calculations at the same time, whereas today’s conventional computers only perform one.
the basis of qc
The classical computer (non-quantum), like the PC or laptop that sits in front of you, uses the language of computers called binary. Binary is a base 2 mathematical language because it only consists of two digits. These are 1’s and 0’s. This is the fundamental unit of information or building block called the bit. A bit, in classical computers, is either a 1 or 0. In quantum computing the fundamental unit of information is a qubit (quantum bit). Qubits form the basis of quantum computing.
Perfect, but what makes a qubit different from a classical bit. Let’s look at the following example to demonstrate the radical contrast between the two. In a classical computer, let’s say we have two bits. These two bits could consist of one of the following combinations: 00 or 01 or 10 or 11. In quantum computing, two qubits can also consist of one of those four aforementioned combinations which are called computational basic states. Now, here is the crux of quantum computing. While a classical pair of bits can store these numbers only one at a time, a pair of qubits can also exist in a superposition of these four basis states or an intermediate (between 0 and 1). What this means is that a pair of qubits can simultaneously consist of all four possible states or combinations (00, 01, 10, 11). Thus, qubits can contain an extremely vast amount of information (in fact, in theory, an infinite amount of information) and this results in quantum computers being exponentially more powerful than classical computers (non-quantum).
This unique property of a qubit (to be able to exist in a superposition of states) arises because of quantum computers following the laws of quantum mechanics, while a classical bit follows the understood laws of classical physics.
the state of qc
In a classical computer we can read out the state of all the bits in the computer at any time. The following 3 bits is in a definite state of 101, and can be read one-zero-one in a classical computer. Due to the property of superposition of a qubit in a quantum computer; it is impossible to determine the exact state of the computer. This means, we cannot determine exactly which superposition state a qubit is in because of their ability to switch from one state to another. Rather, we can only obtain partial information about the state of the computer. This makes it extremely difficult to build a quantum computer because we cannot determine the exact state at any time. Therefore control measures to control the state of qubits must be created, which are called control devices.
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qubit control
Qubits are made up of quantum particles which are: photons, atoms, electrons and ions. These particles need to be controlled in order to create a qubit which cages these particles. Control devices trap these particles and then switch their state. There are four control devices that can be used to create qubits :
Ion traps
Ion traps use magnetic fields to trap ions. At this moment in time, researchers have managed to entangle as many as six ions in a single ion trap. As ion trap technology becomes more established, the number of ions trapped will grow.
Quantum dots
Quantum dots are bits of semiconductor material that contain one or a few electrons. Quantum dots are loaded with electrons, and they can be integrated into electronic devices. The most advanced prototypes today work only at extremely low temperatures.
Semiconductor impurities
It is difficult to make a pure computer chip. Some atoms embedded in these chips are commonly found as impurities (or flaws). There is usually an unwanted atom of some kind in every few billion atoms. Qubits include ‘unwanted’ electrons of atoms intentionally into the semiconductor materials. The state of these electrons can then be controlled using lasers or electric fields.
Superconducting circuits
Superconducting circuits are simply electrical circuits which are made of superconducting material. This means that electrons can flow with almost no resistance at extremely low temperatures. Superconducting circuits can form qubits by the flow of current. The current can be made to flow in both directions at once (simultaneously) in the quantum state of superposition. The world’s first commercial quantum computer, the Orion, uses superconducting circuits. The advantage is that they use millions of electrons instead of controlling individual particles. Superconducting circuits have to work at extremely low temperatures.
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quantum gates
Introduction
We have seen the enormous superiority that qubits have over bits. This means nothing though, if we don’t have a way of manipulating the information in qubits. To manipulate information in a qubit, quantum gates are used.
How quantum gates work
A quantum gate works similar to a classical logic gate. Classical logic gates take bits as input; evaluate and process the input and produce new bits as output. In the example below (refer to diagram CLG), the logic gate takes in 0101 as input, which ‘goes through’ the gate and an output of 10 is produced.
Quantum logic gates also emulate this, but remember quantum gates take in qubits which can exist in a state of superposition. This opens up a whole new dimension of possible solutions and outputs. In the example below (refer to diagram QLG), the quantum gate takes in 010 (a basis computational state), and what would you say it should output? Another basic computational state? No! Instead, and extraordinarily so, it outputs a wave function representing a superposition state. Magic ! This is the weirdness of the quantum world, where things don’t behave how we expect them to. Fortunately, this weirdness can be exploited to achieve greater processing power, and that is the main advantage of quantum gates (and quantum computer in general).
Reversibility
Another property of quantum gates it that they are reversible unlike many classical logic gates. This means that the outputs can be converted back into the original input. Why is this necessary? In order to preserve the quantum state. In order for the gates to be reversible, the number of outputs must be the same as the number of inputs.
the power of qc
The power and capabilities of quantum computing threatens to rock the very foundations of the information age. These capabilities can be used in various fields and can have astounding effects. Referring to the advancement of quantum computing in the “Technologies: The Future of the Global Information Society” report in 2002, Christopher Altman said:
“An omni-linked world populated with intelligent artifacts will bring sweeping changes to virtually every facet of modern life – from science and education to industry and commerce – leaving no segment of society unaffected by its advance.”
As you can ascertain from this quote, all facets of life will change dramatically with the advance of quantum computing such as science & chemistry, and even the security that protects our personal information.
Science & Chemistry
Food, materials, cloths, fuels and every substance in our lives are created using science and chemistry. Numerous advances have been made in chemistry over the past few decades which is due to computer being able to model the structure of complex molecules. Let’s say we want to model the structure of a molecule of a certain type of medicine. In order to model a molecule, the computer has to solve the Schrodinger Equation (SE). This equation, when solved, provides us with the description of matter at the quantum mechanics level (microscopic level). Using this description, the computer can then model the structure of the molecule. The problem is that the equation doubles in difficulty for every electron in the molecule. This means that conventional computers can only model molecules with no more than 30 electrons, anything more and even the high-end supercomputers of today choke.
Quantum computers, on the other hand, are capable of solving the SE much faster and with less hardware. With a quantum computer the difficulty increases by a very small margin with each electron. This means that even very basic quantum computers will be able to outperform supercomputers in simulating molecules, nature and virtually anything. This will result in massive, exponential advances in the field of science and chemistry, and will affect all facets of life, because thousands of more complex molecules and substances will be created every day. In fact the successful application of quantum computers to science and chemistry can save the world! See how, here.
Encryption and security
In the age where buying, banking and almost anything can be done online; security and encryption is imperative. RSA is the most secure encryption that is used today, because even the most advanced supercomputers cannot crack the system. Why? Because in order to break the RSA encryption is reduced to factoring extremely large numbers (300 digit), which even the fastest computers and supercomputers today choke when attempting. In fact it would take hundreds of years to find the factors of a 300 digit integer using the world’s fastest supercomputer, yet by using Shor’s Algorithm on a quantum computer the RSA would be cracked in a heartbeat and rendered obsolete. This is one example of the massive leap in power that quantum computing provides.
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quantum algorithms
The power of quantum computing could only be harnessed if an algorithm could exploit the potential of it. An algorithm is simply a program that is designed for the purpose of solving a certain problem. Without algorithms, we would have no computer (classical or quantum), because there would have been no motivation to build a computer if it could not solve any problems.Similarly nobody wanted to build a quantum computer because there were no algorithms. In 1994 everything changed when Peter Shor, a Bell Labs scientist, wrote an algorithm which would factor large numbers on a quantum computer. This discovery would change the world forever; as engineers and scientists stepped into the potent world of quantum computing. Since then, there have been great advances in the writing of quantum algorithms which are now armed with astonishing sophistication. The latest being able to manipulate 16 qubits, which is the world’s first commercial quantum computer, the
Orion by D-Wave Systems.
how qc can save the world
NP Problems
Nondeterministic polynomial (NP) problems are considered the most difficult problems on earth to solve. With current computers most NP type problems are virtually unsolvable. This is because when a new variable is added, another dimension to the possible solutions is opened. Every value in the problem must be calculated, compared to and then an optimal solution can be found. Conventional computers almost never achieve optimal results, because they are not fast or accurate enough.
Quantum computers, are once again vastly superior , because they can evaluate all possible solutions simultaneously (because of superposition) and then find the optimal solution. The solution is found a lot quicker and is more accurate, than classical computers.
NP problems are everywhere from database searching to pattern-matching to medicine. If all these NP type problems could be solved, life on earth would be thousands of years ahead and extremely more advanced. Quantum computers can, and a paradox may it be, solve unsolvable problems which will define the future of our world…
Saving the world (and changing it)
Imagine if every NP type problem on earth could be solved? Well, stop imagining because it’s just around the corner, when quantum computers will do just this. Just think of the possibilities! Molecules containing hundreds or thousands, even millions of electrons will be able to be modelled by solving the Schrodinger Equation (SE) using quantum computing. This could mean that a cure for AIDS could be found in seconds! Medicine will leap ahead like never before, and hence millions of lives will be saved.
Even more importantly, ‘greener ’ fuels and alternate energy sources can be discovered and the current global warming problem we are facing could be rectified in an instant. Our dependency of oil will end or on the other hand quantum computing may enable us to synthetically reproduce commodities like gold, diamonds and oil. It can bring to an end the countless wars being fought over oil and other sources of wealth. Eventually the very fundamental equations of nature will be solved. More astonishingly and maybe even frighteningly, quantum computers will be able to simulate nature so accurately that virtual reality and the real world will become undistinguishable. In summary, quantum computing has the potential and is very likely to save the world from imploding, and also making it a better, cleaner, safer place.
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the orion of qc
The first commercial quantum computer in the world has been made by D Wave Systems Inc. The quantum computer is call the ‘Orion’. It is made up of 16 qubits which is the most ever for a quantum computer. The Orion was built using a superconducting metal called niobium. In order for qubits to maintain their quantum state, they must be cooled. Therefore, the Orion is supercooled to almost absolute zero.
The biggest advantage of the ‘Orion’ is the ability it has to solve NP probems in just a few cycles. The classical computer takes thousands of cycles and gives less accurate solutions. When the ‘Orion’ was demonstrated in Mountain View (Silicon valley), it solved a Sudoku puzzle in seconds!
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