QUANTUM ENIGMA Summer 2014 Ted McIrvine

(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 (1970-90) & Quantum Computing

(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 2n states.

• A quantum computer, using n bits, is in any quantum

(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.

(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

(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.

(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.

(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?

(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)

(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)

(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

(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

(19)

CQC

2

_{T: AUSTRALIA}

• CQC2_{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.”

(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

(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

(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

(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

(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

(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.