QUANTUM ENIGMA Summer 2014 Ted McIrvine

Transcription

1 QUANTUM ENIGMA Summer 2014 Ted McIrvine June 17: Once Over Lightly & Newtonian Mechanics June 24: Electricity, Magnetism, Light & the Puzzles of 1900 July 1: Atomic Theory, Quantum Theory, Paradoxes and Doubts of the 1930 s & Beyond... July 15: Bell s Theorem ( ) & Quantum Computing July 22: Non-Locality, Conscious Physics, Philosophy

2 2012 NOBEL PRIZE IN PHYSICS Serge Haroche (Collège de France and Ecole Normale Supérieure, Paris, France) David J. Wineland (National Institute of Standards and Technology and University of Colorado Boulder, CO, USA) for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems Techniques for manipulation that enable quantum computers to be considered practical

3 QUANTUM COMPUTERS: DIFFERENCE BETWEEN A QUBIT & A BIT Classical computers store bits, which can have either of two values one or zero. Quantum computers store qubits, which can be in any quantum superposition of a zero and a one.

4 DIFFERENCE BETWEEN A CLASSICAL COMPUTER & A QUANTUM COMPUTER A pair of bits is in one of four states: (0,0), (0,1), (1,0) or (1,1) A pair of qubits is in any quantum superposition of those four states. A normal computer, using n bits, is in one of 2 n states. A quantum computer, using n bits, is in any quantum superposition of those 2 n states.

5 CLASSICAL COMPUTERS: DETERMINISTIC & PROBABILISTIC Consider a three-bit register, with eight possible states (0,0,0), (0,0,1), (0,1,0), (0,1,1), (1,0,0), (1,0,1), (1,1,0), (1,1,1) A classical deterministic computer has a three-bit register in one of those eight states. A classical probabilistic computer has a three-bit register in any of those eight states, with the probability of each given by eight non-negative numbers. Those eight numbers must add to one.

6 QUANTUM COMPUTER A quantum probabilistic computer has a three-bit register in any quantum superposition of those eight states Difference from the classical case: the probability is given by eight complex numbers (the coefficients of an 8-dimensional vector in the complex plane) The numbers don t add to one; instead the sum of the squares of the absolute values add to one

7 QUANTUM COMPUTER The eight-dimensional vector has also phase information (the phase difference between any two coefficients) This phase information is the fundamental difference between a quantum computer and a classical computer When the wave function is collapsed in making a classical reading of the system, the phase information is destroyed

8 PROBABILISTIC COMPUTERS: READING OUT THE ANSWER In the case of a classical probabilistic computer, we sample from the probability distribution on the three-bit register to obtain one answer. In the case of a quantum probabilistic computer, we measure the three-qubit state by collapsing the wave function to a classical distribution, followed by sampling from the probability distribution of that classical reduction. This process destroys the original quantum state.

9 QUANTUM DECOHERENCE Interactions with the external world will cause the system to lose its quantum coherence. The system must be isolated from its environment. Decoherence times for systems under consideration range between nanoseconds and seconds. Quantum computers require running at low temperatures (often below.01k)

10 QUANTUM COMPUTER: APPLICATIONS Why would we go to the trouble and expense of creating a quantum computer? Because of the great increase in speed in tackling problems such as: Integer factorization of large integers (used in cryptography). Simulation of quantum processes in chemistry & solid state physics. Various mathematical proofs.

11 REQUIREMENTS FOR A PRACTICAL & USEFUL QUANTUM COMPUTER Scalable technology... so as to increase the number of qubits Easily read qubits Qubits that can be initialized to arbitrary values & other engineering desiderata

12 AMONG THE AMERICAN R&D SPONSORS NASA Ames Laboratory Lockheed Martin Northrup Grumann Google Quantum Artificial Intelligence Laboratory Microsoft sponsoring multiple sites BBN (Bolt Beranek Newman) on behalf of whom? NSA - $79.7M per year

13 R&D SITES: NORTH AMERICA University of Michigan (since 2005) Yale University (since 2009) University of Southern California University of California Santa Barbara Iowa State University Lockheed Martin IBM D-Wave Systems (Burnaby, BC, Canada) & others...

14 R&D: EUROPE Kavli Institute of Nanoscience (Delft, Netherlands) ETHZ (Eidgenössische Technische Hochschule Zürich, Switzerland) University of Bristol (England) & many others...

15 R&D: ASIA The Chinese government is backing 90 separate projects aimed at a fully-functional quantum computer. The Centre for Quantum Information and Quantum Computation (CQIQC) was set up in 2010 at the Indian Institute of Science. RIKEN (Japan) & others...

16 QUANTUM INFORMATION PROCESSING PROJECT: JAPAN The FIRST program ( Funding Innovative R&D on Science and Technology ) was in the 2009 supplemental budget of the Japanese government. The aim is world leading R&D that will strengthen Japan s international competitiveness in the mid to long term. The Quantum Information Processing project was one of the thirty projects selected out of 565 applications.

17 JFLI: JAPANESE FRENCH LABORATORY FOR INFORMATICS Research Team Members from: The Graduate University for Advanced Studies, Japan University of Tokyo Keio University Université Paris Diderot Telecom ParisTech Laboratoire d Informatique Grenoble (LIG)

18 JFLI: JAPANESE FRENCH LABORATORY FOR INFORMATICS Specific research topics appear are in Computer Science, not in the physical implementation of devices: Quantum Cryptography and Communication Quantum Algorithms Quantum computation and measurement Feasibility of large scale Quantum computation Robustness of QIP protocols Fault-tolerant quantum computation

19 CQC 2 T: AUSTRALIA CQC 2 T - The Australian Centre of Excellence for Quantum Computation & Communication Technology An international effort to develop the science and technology of a global quantum computing information network, encompassing ultra-fast quantum computation, absolutely secure quantum communication and distributed quantum information processing. web site:

20 QUANTUM COMPUTERS: CQC 2 T: AUSTRALIA Established in 2011 with funding from: Australian Research Council Department of Defence (Australia) US Army Research Office Semiconductor Research Corporation the participating Australian universities

21 QUANTUM COMPUTERS: CQC 2 T: AUSTRALIA Seven participating Australian universities: University of New South Wales Australian National University University of Melbourne Griffith University University of Queensland UNSW Canberra University of Sydney

22 POSSIBLE PHYSICAL SYSTEMS Research is underway on more than a dozen configurations. These include: SQUIDs (Superconducting Quantum Interference Devices) & Josephson Junctions Trapped Ions Neutral atoms trapped in an optical lattice Quantum dots (double dots with one ambiguous electron)

23 POSSIBLE PHYSICAL SYSTEMS Other possible configurations: Nuclear Magnetic Resonance in a liquid Nuclear Magnetic Resonance in a solid Diamond-based Nuclear Magnetic Resonance Diamond-based Electron Spin Resonance Electron Spin Resonance in Fullerene

24 POSSIBLE PHYSICAL SYSTEMS Other possible configurations: Electron on Helium Atoms in High-Finesse Optical Cavities A Bose Condensate Holes entrained in Electrostatic Traps in a Transistor Rare Earth Ion-Doped Crystal especially the state of dopants in an optical fiber & others...

25 D-WAVE SYSTEMS D-Wave Systems in Burnaby, BC is a small high tech startup company that has received publicity (e.g. Time Magazine). For $10M, you can buy a D-Wave Two computer that they say operates through adiabatic quantum annealing. Some academic sources have expressed doubt that it is a quantum computer, although recent disclosures have reduced the uncertainty. The existing $10M machines are slower than a classical computer on almost all calculations.

26 PHASED PRODUCT PLANNING The orderly development of high technology products moves through five phases: Concept Research Development Design Maintenance

27 CURRENT STATE OF QUANTUM COMPUTERS Until a dominant product concept is found, many possibilities will be explored. Things will not settle down until there are decisions about: Which quantum algorithms are best to use? Which physical system is best to contain the qubits? How will a small array of qubits be scaled up to create a large computer?

28 CURRENT STATE OF QUANTUM COMPUTERS Quantum computing is in its infancy. We are not even into the development phase for quantum computers. We are in the concept and research phases. Researchers seek the correct combination for a useful product.