Norman Littlejohn COSC480

 Quantum Computing  History  How it works  Usage

 The number of transistors in a processor double every ~18 months  What happens in the year ?  The next step: Quantum Computing

 A device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data  Harness the power of atoms and molecules to perform memory and processing tasks

 Argonne National Laboratory around 30 years ago  Paul Benioff – credited for first applying quantum theory to computers in 1981

 Create an quantum turing machine  Turing machine – theoretical device consisting of tape of unlimited length divided into squares which can hold 0 or 1. Instructions are read off of the tape. One calculation at a time  Quantum Turing – tape and read/write head exist in quantum state. The positions can be 0 or 1, or a superposition of 0 or 1. One million calculations at a time

 Superposition - a fundamental principle of quantum mechanics. It holds that a physical system (say, an electron) exists partly in all its particular, theoretically possible states (or, configuration of its properties) simultaneously; but, when measured, it gives a result corresponding to only one of the possible configurations

 Modern computers work with bits in one of two states ( 0 or 1 ).  Quantum computers encode information as quantum bits, or qubits, which can exist in superposition, which allows more states.

 Qubits represent atoms, ions, photons, or electrons and their respective control device that work together to act as computer memory and a processor.  30-qubit processor = modern computer running at 10 teraflops (10 trillion floating- point operations per second).  Typical desktops measured in gigaflops

 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.

 Entanglement – attempting to look at subatomic particles could bump them and change the value.  Looking at a qubit in superposition to determine the value will assume the value of 0 or 1, but not both which is the same function of digital computers.

 Measure indirectly to preserve integrity  Outside force to two atoms makes them entangled. When disturbed, one atom will choose a spin (or value), and the second atom will choose the opposite spin.

 1998 – Los Alamos and MIT researchers  Spread a single qubit across three nuclear spins. Spreading it made it harder to corrupt and allowed researchers to use entanglement to study reactions indirectly

 2000 – Los Alamos Lab  7-qubit quantum computer within a single drop of liquid.  Used nuclear magnetic resonance (NMR) to manipulate particles in the atomic nuclei of molecules of trans-crotonic acid. Electromagnetic pulses forced the particles to line up. Particles in position paralell or counter to the magnetic field let the quantum computer mimic information encoding  Trans-crotonic acid = fluid of 6H atoms and 4C atoms.

 2001 – IBM and Stanford University  Demonstrated Shor’s Algorithm (finding prime factors of numbers).  7-qubits

 2005 – Institute of Quantum Optics and Quantum Information (Innsbruck University)  First qubyte created (8 qubits)  Made through use of ion traps

 2006 – Waterloo and Massachusetts  Quantum control on a 12-qubit system

 2007 Canadian Company D-Wave  Demonstration of 16-qubit quantum computer  Computer solved a sudoku puzzle and other pattern matching problems

 Promised a practical system by 2008, but many believed it to be impossible  D-Wave One D-Wave One  D-Wave Homepage D-Wave Homepage

 Ability to factor large numbers allows for useful decoding and encoding secret information  Modern encryption methods are simple compared to quantum computers’ methods  Search large databases in a fraction of time it would take modern computers

 Think Big Think Big

 Quantum Computing:  History  Development  How it works  Usage