Quantum computersSlide 2Slide 3Slide 4Slide 5Slide 6Problems and LimitsQuantum computersQuantum computersDid you know that Bill Gates may need to go back to school? Do you know what the U.S. government spent $1 million on in 1995 and $30 Million on in 2001?What physicists all over the world are into?Governments, universities and computer companies are investing and working on the hot new commodity, quantum computers.In 1965, Intel’s co-founder Gordon Moore saw that the number of transistors and the speed of computer chips were doubling about every 18 months. If technology followed Moore’s Law, then the shrinking size of circuitry packed into silicon chips would eventually reach a point where individual elements would be no larger than a few atoms. Here, a problem arises because at the atomic scale of physical laws that govern the behavior and properties of the circuit are inherently quantum in nature, not classical. The limits of classical computers and its computations brought up the idea of computers based on quantum mechanics. 1970s and 1980s: Theorists proposed idea of quantum computers.1985: Deutsh of Oxford University wrote paper on quantum computers that went unnoticed. No one doubted quantum computer would work, but no point to this difficult and expensive task.1994, A computer scientist at AT&T Bell Labs suggested that the strange, almost spooky way that a quantum computer could go about its business made it the perfect code-breaking machine.A hot commodity is inspired.1996: first quantum computer by IBM’s Chuang. This computer and others to follow look more like chemistry experiments than computers, but then, they are!This first computer was a two-qubit one. You’ve heard of a bit, you heard of a byte; but what do you ask is a qubit?Qubits are the heart of the atoms, the nucleis with certain quantum properties that allow them to work together. Action sometimes looks like a wave.Qubits can also be electrons or photons depending on scientist’s choice. Qubits give a quantum computer its power and are simultaneously the computer’s processor and its memory. The qubits are the fundamental unit of information but are not binary.Classical vs. Quantum: the difference?The logic circuits of traditional computers work by detecting discrete differences in the voltage passing through electronic gates: a high voltage indicates a binary one and a low voltage, a zero. The smallest unit in digital realm is a bit which can represent a 1 or a 0. A qubit can be a 1 or 0 or both simultaneously! A single spinning qubit can be in two states at once and do the job of 2 classical bits operating in parallel. Put another way, a traditional memory register with eight bits can store only one of a possible 256 digital “words”, but a quantum register with eight qubits can represent and compute all 256 words at once.In traditional computer architecture, the expressions and or and not are embodied in the electrical circuits. To manipulate qubits, quantum circuits use nuclear magnetic resonance (NMR) or laser pulses to obtain these operations. NMR,which is already used in chemical analysis and hospital image scanning, is used to measure the small amounts of energy castoff by the spinning atoms. Other methods to develop quantum computers include electron spins confined in a semiconductor nanostructure, nuclear spins associated with single atom impurities, etc.There’s not one set way to do this.We go back again to what’s the point of this? As mentioned by Shor, the code-breaking machine is of great interest. Today, factoring a large number is very difficult. For this and certain jobs, quantum computers will be able to put even the best of today’s supercomputers in the shade by using their trick that ordinary computers cannot truly master- parallel processing. Although supercomputers are fast, they can like all other digital computers, do only one thing at a time. Even so-called “parallel” computers now available are just collections of machines that each do only one thing at a time. But a quantum computer is truly parallel, doing many different things simultaneously in the same piece of equipment. Indeed, IBM’s Almaden Research Center performed the world’s most complicated quantum computer calculation to date, using a billion-billion custom-designed molecules in a test-tube to become a seven-qubit computer that solved the heart of many of today’s data security cryptographic systems. This ability is of great interest to governments who use RSA (a common and the best encryption code that relies on factoring large numbers). The quantum computer will be able to factor a 400-digit number in a year, while a conventional computer would need to work on it for billions of years. Due to this future ability, three companies have already formed to market secure communication systems based on quantum factoring. Another use for a quantum computer presented by Lou Grover, a computer scientist at Bell Labs, is to search unsorted databases. If you were to sift through 10,000 pieces of paper scattered about your desk in search of one important memo, you would have to be prepared to scan 5,000 of them to have an even chance of finding it. By assigning each parallel computation to pursue a different choice, a quantum computer could do the same in 40 runs.Problems and Limits•Quantum computer leaks information like a water though a sieve.•Error correction, coherence and hardware architecture.•Limitation in liquid NMR approach.•Delicate nature of